Electrochemical Engineering Research Articles

Hydroxyl-Binding Induced Hydrogen Bond Network Connectivity on Ru-based Catalysts for Efficient Alkaline Hydrogen Oxidation Electrocatalysis.

Understanding the role of adsorbed intermediates at the polarized catalyst-electrolyte interface on the structure of electrical double layer (EDL) is essential for developing highly efficient electrocatalysts. Here, we prepared a series of unconventional face-centered-cubic (fcc) phase Ru-based catalysts (i.e. fcc-Ru, fcc-RuCr, and fcc-RuCrW) by rational tuning the binding energetics of hydroxyl intermediate to engineer the electrochemical interface and boost the performance of alkaline hydrogen oxidation reaction (HOR). The introduction of oxyphilic metals Cr and W can regulate the orbital occupation of Ru, promote the adsorption of hydroxyl species, resulting in an anomalous behavior that HOR performance under alkaline media exceeds acidic media. Experimental results and theoretical calculations unravel that the modulated adsorption of hydroxyl species on the electrode surface are responsible for the reconstruction of interfacial water structure and dynamic evolution of free water molecules from nearest to the electrode surface to above the gap region in the EDL, thereby leading to significantly increased water connectivity and hydrogen bond network. Our work reveals a new understanding of the surface intermediates in controlling the dynamic process of interfacial water and hydrogen bonding network in HOR electrocatalysis, and will guide rational design of advanced electrocatalysts through electrochemical interfacial engineering.

Hydroxyl‐Binding Induced Hydrogen Bond Network Connectivity on Ru‐based Catalysts for Efficient Alkaline Hydrogen Oxidation Electrocatalysis

Understanding the role of adsorbed intermediates at the polarized catalyst‐electrolyte interface on the structure of electrical double layer (EDL) is essential for developing highly efficient electrocatalysts. Here, we prepared a series of unconventional face‐centered‐cubic (fcc) phase Ru‐based catalysts (i.e. fcc‐Ru, fcc‐RuCr, and fcc‐RuCrW) by rational tuning the binding energetics of hydroxyl intermediate to engineer the electrochemical interface and boost the performance of alkaline hydrogen oxidation reaction (HOR). The introduction of oxyphilic metals Cr and W can regulate the orbital occupation of Ru, promote the adsorption of hydroxyl species, resulting in an anomalous behavior that HOR performance under alkaline media exceeds acidic media. Experimental results and theoretical calculations unravel that the modulated adsorption of hydroxyl species on the electrode surface are responsible for the reconstruction of interfacial water structure and dynamic evolution of free water molecules from nearest to the electrode surface to above the gap region in the EDL, thereby leading to significantly increased water connectivity and hydrogen bond network. Our work reveals a new understanding of the surface intermediates in controlling the dynamic process of interfacial water and hydrogen bonding network in HOR electrocatalysis, and will guide rational design of advanced electrocatalysts through electrochemical interfacial engineering.

Unveiling the Structure and Dissociation of Interfacial Water on RuO2 for Efficient Acidic Oxygen Evolution Reaction.

Understanding the structure and dynamic process of interfacial water molecules at the catalyst-electrolyte interface on acidic oxygen evolution reaction (OER) kinetics is highly desirable for the development of proton exchange membrane water electrolyzers. Herein, we construct a series of p-block metallic elements (Ga, In, Sn) doped RuO2 catalysts with manipulated electronic structure and Ru-O covalency to investigate the effect of electrochemical interfacial engineering on the improvement of acidic OER activity. Associated with operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy measurements and theoretical analysis, we uncover the free-H2O enriched local environment and dynamic evolution from 4-coordinated hydrogen-bonded water and 2-coordinated hydrogen-bonded water to free-H2O on the surface of Ga-RuO2, are responsible for the optimized connectivity of hydrogen bonding network in the electrical double layer by promoting solvent reorganization. In addition, the structurally ordered interfacial water molecules facilitate high-efficiency proton-coupled electron transfer across the interface, leading to reduced energy barrier of the follow-up dissociation process and enhanced acidic OER performance. This work highlights the key role of structure and dynamic process of interfacial water for acidic OER, and demonstrates the electrochemical interfacial engineering as an efficient strategy to design high-performance electrocatalysts.

Development of a highly stable IrO2-RuO2-Ta2O5/Ti with fluorine doped nanotube interlayer

Fluorine-doped titanium oxide nanotubes were studied as a coating interlayer for IrO2-RuO2-Ta2O5/Ti to retard the passivation of titanium substrates and enhance anode life and corrosion characteristics. Nanotubes were produced by anodizing the substrate at 10, 20, and 40 V in HF, and their effect on the microstructure of the coating was assessed using FE-SEM. Additionally, EIS and ALT measurements were conducted to investigate this coating's electrochemical behavior. Results showed that titanium oxide nanotubes with a smaller diameter would improve the performance and increase the life of the anode (IrO2-RuO2-Ta2O5/Ti). Likewise, the diameter of the nanotubes demonstrates a direct relationship with anodizing voltage. Furthermore, high voltages during anodizing resulted in an etched surface that was not ideal for an interlayer. All an all, it was concluded that the layer anodized at 10 V, with smaller-diameter tubes and a higher number of walls, could result in a product with high corrosion resistance and 80 % excess lifetime compared to a bare titanium substrate. This study provides valuable insights for engineering applications, demonstrating the potential for enhanced anode design in corrosion-sensitive environments in electrochemical engineering, water treatment, or fuel cells and electrolyzers where durability of the anodes are crucial.

Enhanced propanethiol biodegradation by an optimized propanethiol oxidoreductase in microbial cells within an electrode bioreactor

Propanethiol oxidoreductase (PTO) is a novel thiol-oxidizing enzyme from Pseudomonas putida S-1 that utilizes thiols as the sole nutrition source. This enzyme has shown application potential in the bioremediation of thiols, its substrate selectivity, however, has not yet been elucidated. This study reveals that PTO exhibits catalytic activity towards ethanethiol, propanethiol, and butanethiol, but not methanethiol or phenylmethanethiol, indicating unique substrate specificity. Through directed evolution and semi-rational design, we engineered a PTO mutant (A54V&G316T) with twice the specific activity towards propanethiol than the wild type (from 17.3 to 40.7μg/mg/h). Applying voltage in electrode bioreactors enhanced the microbial degradation of propanethiol, with the mutant PTO further accelerating this process. Both non-native expression in E. coli and native expression in engineered P. putida S-1 demonstrated the mutant PTO's effectiveness in increasing PT removal rates. The PT degradation efficiency of engineered P. putida S-1 increases by 3-fold compared to the wild-type in the first 5hours. These findings highlight the potential of combining metabolic and electrochemical engineering to enhance bioremediation of toxic compounds. The engineered PTO mutant improves PT degradation efficiency and broadens its application in practical bioremediation strategies.

Electrochemical Engineering of Anode with Zincophilic Polymer Interface for Reversible Zinc Battery

AbstractAqueous rechargeable zinc‐ion batteries are emerging as green and safe energy devices owing to their high energy density and eco‐friendliness. The bottleneck is the inhomogeneous nucleation resulting in the growth of Zn dendrites and the parasitic side reactions at the anode. Herein, an electrochemical anode engineering strategy is demonstrated to curb the uncontrolled dendritic growth and side reactions. It involves the in situ generation of a solid‐electrolyte interface based on a Zn nanoparticle‐embedded poly(acrylic acid) hybrid layer (PAA‐nZn) on the anode. The homogeneously distributed polar functionalities and porous nature of the polymer regulate the uniform zinc ion flux, and the embedded zinc particle serves as nucleation sites for zinc plating. The hybrid layer reduces the nucleation overpotential and promotes instantaneous nucleation. The symmetrical cell made with PAA‐nZn@Zn has a lifecycle of >860 h with a voltage gap of 28 mV. The full cell fabricated by pairing the engineered anode with α‐MnO2 cathode showed a high discharge specific capacity of 238.3 mAh g−1 at 0.2 A g−1 with a capacity retention of 81.76% after 200 cycles and a long lifecycle. The electrochemical engineering of the anode suppresses the dendritic growth and protects the anode from unwanted side reactions and passivation.

Understanding the Electric Double Layer at the Electrode-Electrolyte Interface: Part I - No Ion Specific Adsorption.

We present a comprehensive mean-field model that takes into account the key components of modern electrical double layer theory at the interface between an electrode and an electrolyte solution. The model considers short-range specific interactions between different species, including electrode-ion repulsion, the hydration of ions, dielectric saturation of solvent (water), and excluded volume (steric) interactions between species. By solving a modified Poisson-Boltzmann equation and using the appropriate results of quantum chemistry calculations on the hydration of ions, we can accurately approximate the differential capacitance profiles of aqueous electrolyte solutions at the boundary with a silver electrode. The specific interactions between the ions and the electrodes in the systems under considerationare assumed to be significantly weaker than their Coulomb interactions. A novel aspect of our research is the investigation of the impact of short-range ion-water interactions on the differential capacitance, which provides new insights into the behavior of the electrical double layer. This model holds the potential to be useful for electrochemical engineers working on the development of supercapacitors and related electrochemical energy storage devices. It serves as a basis for future modeling of electrolyte systems on real electrodes, especially in scenarios where chemical ion-electrode interactions are significant.

(Invited) Sequential Development of Continuous Electro-Osmotic Dewatering for Phosphatic Clay Suspensions

The beneficiation plant associated with a typical Florida phosphate mining operation produces more than 6,300 L/s of a dilute 2-3 wt.% suspension of phosphatic clay. The clay-water suspension is pumped into large impoundments called clay settling areas in which partial separation is achieved by hindered settling and self-consolidation. As clay settles, the supernatant water is recycled for use in the beneficiation plant. A top crust is formed after a few years, but the clay beneath the crust has a large water content and a pseudo-plastic character that limits the amount of weight the settling area can support. Clay settling areas cover roughly 390 square kilometers of land in Florida. Uses for the land are limited by the properties of the clay that leave the settling areas unstable, even after 50 years of elapsed time. In addition, failure of the impoundments has caused major releases into local rivers.1 Research in use of electrokinetic phenomena to accelerate the dewatering process of phosphatic clay has been active for more than 50 years.2,3 The use of an electric field to separate the water from the solids is attractive because the inherent stability of the clay suspension is due, in part, to the surface charges residing on the platelets. This presentation will describe the results of a 7-year research project, funded by Mosaic, to create an electrokinetic alternative to the creation of clay settling areas. Through a systematic development of prototypes, from batch4,5 to semi-continuous with emphasis on water clarification6 to semi-continuous with emphasis on solids extraction, our team has developed a fully continuous prototype using electrokinetic dewatering. The fully continuous prototype itself underwent several prototype designs, culminating in a single-stage design for continuous electro-osmotic dewatering of phosphatic clay suspensions that demonstrated efficient production of a dewatered cake with a solids content of 35 wt.% at a dry-clay production rate of 4.5 kg/h m2 from a feed clay of 10 wt.%.7,8 The results were supported by measurements of yield stress and a mathematical model that accounted for compressibility of the cake and for both electro-osmotic and hydraulic permeability.9 Patents were published that correspond to the above stages of development.10-12 References Damage Cases and Environmental Releases from Mines and Mineral Processing Sites, U.S. Environmental Protection Agency, Washington, DC, 1997.A. Dizon and M. E. Orazem, “Advances and Challenges of Electrokinetic Dewatering of Clays and Soils,” Current Opinion in Electrochemistry, 22 (2020), 17-24.J. Q. Shang and K. Y. Lo, “Electrokinetic Dewatering of a Phosphate Clay,” Journal of Hazardous Materials, 55 (1997), 117-133J. P. McKinney and M. E. Orazem, “A Constitutive Relationship for Electrokinetic Dewatering of Phosphatic Clay Slurries,” Minerals & Metallurgical Processing, 28 (2011), 49-54.J. P. McKinney and M. E. Orazem, “Electrokinetic Dewatering Phosphatic Clay Settling Areas: Numerical Simulation and Economic Assessment,” Minerals & Metallurgical Processing, 28 (2011), 71-76.R. Kong and M. E. Orazem, “Semicontinuous Electrokinetic Dewatering of Phosphatic Clay Suspensions,” Electrochimica Acta, 140 (2014), 438-446.R. Kong, A. Dizon, S. Moghaddam, and M. E. Orazem, “Development of Fully-Continuous Electrokinetic Dewatering of Phosphatic Clay Suspensions,” in Electrochemical Engineering: From Discovery to Product, Volume XVIII of Advances in Electrochemical Science and Engineering, R. Alkire, P. N. Bartlett, and M. Koper, editors, John Wiley & Sons, Hoboken, 2018, 159-192.A. Dizon and M. E. Orazem, “Efficient Continuous Electrokinetic Dewatering of Phosphatic Clay Suspensions,” Electrochimica Acta, 298 (2018), 134-141.A. Dizon and M. E. Orazem, “Mathematical Model and Optimization of Continuous Electro-Osmotic Dewatering,” Electrochimica Acta, 304 (2019) 42-53.M. E. Orazem and R. Kong, “Electrokinetic Dewatering of Phosphatic Clay Suspensions,” U.S. Patent No. 10,486,108 B2, Issued: November 22, 2019.M. E. Orazem, R. Kong, S. Moghaddam, H. Lai, D. Yu, Y. Huang, and D. Bloomquist, “Continuous Electrokinetic Dewatering of Phosphatic Clay Suspensions,” U.S. Patent No. 10,315,165 B2, Issued: June 11, 2019.M. E. Orazem and A. R. Dizon, “Device for Efficient Continuous Electrokinetic Dewatering of Phosphatic Clay Suspensions,” U.S. Patent No. 11,208,342 B2, Issued: Dec. 28, 2021.

(Henry Linford Award) Overcoming Challenges in Teaching Electrochemical Engineering

Electrochemical engineering is a highly interdisciplinary topic, requiring some preliminary knowledge of chemistry, material science, transport, kinetics, and process design. The major challenge in teaching the topic is that unlike most classes, where all students are ‘in-step’ in terms of their preparation, electrochemical engineering courses typically draw students from different disciplines (e.g., chemical engineering, chemistry, material science, biomedical engineering) with different background and preparation. This problem is further exacerbated in teaching electrochemical engineering short courses, which are typically attended by practicing engineers having quite different backgrounds, experience levels, and interests.When first encountering these issues, I thought that the best approach is to start from the basics, and obtain, through detailed mathematical derivations, very convincingly, the relevant equations. I could not be more wrong: students quickly lost interest, and the practical significance was often missed. I found out, that it is much more effective to first describe the issues and relevancy of the topic, and then, while still emphasizing the fundamentals, only outline the detailed derivations and skip to the final results, explaining the assumptions and limitations, while focusing on the applications and use. The students were still given class notes detailing the derivations and were directed to appropriate book chapters and publications for further reading.In terms of course content, I followed my admired and memorable teacher, Charles Tobias, who first introduced me, and so many others, to electrochemical engineering. Starting with ionic conduction and transport, and moving on to electrochemical thermodynamics, overpotentials, current distributions, multi-components and alloy deposition, transient effects, and scaling. Each topic was accompanied by relevant examples and homework problems which were later reviewed in class. I found out that it was not an effective use of class time to provide detailed discussion of specific electrochemical process technologies, which the students could read about in textbooks. Consequently, just one class period was devoted for brief discussion of each of the following: batteries and fuel-cells, electroplating, electrowinning and electrorefining, electrolytic processes, and corrosion. Emphasis was placed on discussing the fundamentals, issues, and major challenges for each. Students had the opportunity for in-depth study of additional specific applications by preparing and presenting in class a term-paper. To minimize direct reproduction from the literature, students had to indicate and discuss relevancy to fundamentals studied in class. Students could select their own topics and thereby relate the class material to their own disciplinary interests.To foster critical thinking and discussion, and to integrate the material taught, comprehensive case studies were presented and discussed in class. These case studies included among others, topics related to my own research, including scaling analysis, roughness evolution and dendritic growth, bottom-up plating of semi-conductor interconnects, and periodic reverse plating. These will be discussed in the oral presentation in more detail.I would like to conclude by thanking all my former students, who enriched my life so much, and whom I treasure as my ‘academic family’. Lastly and very importantly, I thank my dear friends and colleagues at Case Western Reserve University who made my teaching and research there most enjoyable, through stimulating discussions and close friendships.

Framework and Initial Steps Towards Industry-Relevant Undergraduate Electrochemical Engineering Education

It is widely expected that the use of electrochemical processes will grow rapidly in the coming decade. This growing industry requires a commensurate workforce. However, currently there is little educational infrastructure nationally to provide the number of well-educated incoming engineers and scientists that are needed. Using a design-based research approach, we have developed a framework for curricular development in undergraduate electrochemical engineering, and report here on the first author’s first course offering as the beginning of an iterative refinement process.Our education and research framework is outlined in Figure 1, which illustrates the four main aspects of the project – learning goals, tools, courses, and research – and shows how they are connected. There are two learning goals for students. First, the development of conceptual understanding of electrochemical topics enables them to develop the knowledge structures needed to access and operationalize the content in new contexts, such as in industrial practice. Second, engaging students in disciplinary practices provides an authentic experience of the sociotechnical work faced by engineers in industry. These goals will be realized using tools housed in the Concept Warehouse, an online instructional tool constructed by members of our research team. Tools include concept questions provided to students in class to develop their conceptual understanding, which will then be assessed using a concept inventory in development. An industrially-situated virtual laboratory will allow students to experience a realistic task that engages them in both knowledge practices and social practices of professional engineers. Instructors at a range of institutions, beginning with Tufts University, will teach electrochemical engineering courses. They will design the courses according to how they best fit their individual context, but all courses will incorporate the two learning goals and will be supported by the three tools. The project will be supported by a comprehensive research plan that contains two studies – an interview study and a design-based research (DBR) study. First, we plan to interview practicing engineers in the electrochemistry industry to understand both the conceptual knowledge they rely on (for development of the concept inventory) and disciplinary practices they use in their work (to inform the industrially-situated virtual laboratory). Second, using a DBR approach, we will utilize multiple data sources to both improve the instructional design of these courses and develop transferable knowledge about the development of conceptual understanding and disciplinary practices using these instructional tools.In this work, we report on the development of the framework and on the electrochemical engineering course developed and delivered in Fall 2024 by the first author, a post-doctoral fellow at Tufts University, as a pilot. This was also the first author’s first solo course delivery, and general insights on this process will also be shared. The course was offered to 13 students, of whom 8 were undergraduate chemical engineering students, one was a master’s student, and 4 were PhD students. The first half of the course centered electrochemistry fundamentals, using Electrochemical Engineering by Thomas Fuller and John Harb as a reference text, and emphasized conceptual understanding using concept questions and culminating in an entirely conceptual mid-term exam. In the second half of the course, students explored practical applications of electrochemistry, supported by conversations with industry professionals, culminating in a final project on an application of interest for each student.Finally, we discuss next steps in this project, in particular ongoing development of a virtual laboratory and concept inventory, as well as inter-institutional collaboration. Figure 1

Revitalizing Electrochemical Science and Engineering Education to Create a Clean Energy Workforce

Electrochemical science, engineering, and technology education and workforce development are central to the ongoing clean energy transition. In particular, I will highlight battery, hydrogen, and microelectronics industries as drivers. I then highlight a unique Electrochemistry-Technology-focused Graduate program launched through the Oregon Center for Electrochemistry in 2020. At the master’s level, the accelerated program consists of six core electrochemistry science and engineering lecture, laboratory, and project-based courses over either two or three academic quarters. In addition to core electrochemistry knowledge spanning thermodynamics, transport, kinetics, and device technology, emphasis is placed on problem solving, data analysis, programming (particularly in Python) and professional development and this additional content is embedded throughout all the core lecture and laboratory courses. Students are also introduced to continuum-level electrochemical simulations, with an emphasis on understanding the effects of boundary conditions on the simulation output. They also complete a team-based applied project sponsored by industry partners. The program ends with a nine-month paid internship leading to a master’s degree and career in the electrochemistry industry after 15 months.The coursework is also open to PhD students and postdoctoral scholars who go on to serve as near peer mentors and teaching assistants in the program in future years, directly synergistic with their research, and building community around electrochemistry. A new BS-MS program leveraging the above has launched in 2023, allowing University of Oregon students to complete coursework for both BS and MS in just four years yielding an incredibly high return on tuition and time investment in terms of career potential and earnings. Key to the success of the programs is very low administrative overhead with technical faculty/staff leading all efforts and a transparent budget model to fund the program based on tuition return.

(Keynote) Unified Quantum Theory of Electrochemical Kinetics Based on Coupled Ion-Electron Transfer

A general theory of coupled ion–electron transfer (CIET) is presented, which unifies quantum kinetics of electron transfer (ET) with classical kinetics of bond-breaking ion transfer (IT) in a general framework of non-equilibrium thermodynamics [1]. In the limit of large reorganization energy, the theory predicts Marcus kinetics of “electron-coupled ion transfer” (ECIT). In the limit of large ion-transfer energies, the theory predicts generalized Butler–Volmer kinetics of “ion-coupled electron transfer” (ICET), where the charge transfer coefficient and exchange current are connected to microscopic properties of the electrode/electrolyte interface. In the ICET regime, the reductive and oxidative branches of Tafel’s law are predicted to hold over a wide but finite range of overpotentials, bounded by the ion-transfer energies for oxidation and reduction, respectively. The probability distribution of transferring electron energies in CIET smoothly interpolates between a shifted Gaussian distribution for ECIT (as in the Gerischer–Marcus theory of ET) to an asymmetric, fat-tailed Meixner distribution centered at the Fermi level for ICET. The latter may help interpret asymmetric line shapes in x-ray photo-electron spectroscopy (XPS) and Auger electron spectroscopy (AES) for oxidized metal surfaces in terms of shake-up relaxation of the ionized atom and its image polaron by ICET. In the limit of large overpotentials, the theory predicts a transition to inverted Marcus ECIT, leading to a universal reaction-limited current for metal electrodes, dominated by barrierless quantum transitions. Uniformly valid, closed-form asymptotic approximations are derived that smoothly transition between the limiting rate expressions for ICET and ECIT for metal electrodes, using simple but accurate mathematical functions. The theory is applied to lithium intercalation in lithium iron phosphate (LFP) and found to provide a consistent description of the observed current dependence on overpotential, temperature and concentration, learned from x-ray images [2]. CIET theory thus provides a critical bridge between quantum electrochemistry and electrochemical engineering.[1] M. Z. Bazant, Unified quantum theory of electrochemical kinetics by coupled ion-electron transfer, Faraday Discussions 246, 60-124 (2023).[2] H. Zhao, H. D. Deng, A. E. Cohen, J. Lim, Y. Li, D. Fraggedakis, B. Jiang, B. D. Storey, W. C. Chueh, R. D. Braatz, and M. Z. Bazant, Learning heterogeneous reaction kinetics from X-ray movies pixel-by-pixel, Nature 621, 289-294 (2023). Figure 1

Incorporating Electrochemistry and Battery Technology in an Undergraduate Materials Science Course

Electrochemical devices and systems are ubiquitous in many engineering disciplines, yet basic electrochemistry principles are rarely covered in the typical undergraduate engineering curriculum. This presents a barrier for young engineers aspiring to make contributions to this fast-growing field, as well as primary investigators in electrochemical engineering at undergraduate-only institutions. In the field of mechanical engineering, one of the oldest and arguably the broadest engineering disciplines, energy storage and conversion are covered in depth at the undergraduate level. However, electrochemical energy storage and conversion are only briefly glanced, if at all. As part of curriculum development in a new undergraduate mechanical engineering program, electrochemistry fundamentals, with a focus on applications to battery technology, were deliberately incorporated into a second-year materials science course.Undergraduate materials science courses typically focus on general process-structure-property relationships of different engineering materials, and this course is no different. Instead of covering only traditional materials, significant time is also devoted to battery materials, which are very relevant and poised for exponential growth in this era of electric vehicles and renewable energy storage. The course includes instruction on basic electrochemical principles, a survey of functional materials used in common electrochemical devices and their properties, as well as a short lab project where students are guided through the steps of constructing a simple coin-cell lithium-ion battery, arguably the most dominant of all battery chemistries. Classroom discussion also includes the environmental impacts of sourcing raw battery materials and end-of-life disposal practices, which, given current projections, will lead to a substantial sustainability problem as the battery market grows with electric vehicle uptake. Emerging battery technologies that seek to address the challenges of the current generation of batteries are also introduced. Students are also asked to give a short presentation after researching additional topics in the field that are of interest to them. Overall, the course aims to help modernize the undergraduate mechanical engineering curriculum by incorporating electrochemistry principles and battery technology into a core course.

(Invited) Achieving Circularity in the Battery Industry through Salt Splitting Electrolysis

In an era focused on sustainability, Aepnus Technology introduces a transformative approach in electrochemical engineering that enables circularity in the manufacturing of battery chemicals. Aepnus’ innovation centers on advanced gas diffusion electrodes (GDEs), engineered to significantly boost efficiency and lower the costs of electrolytic salt splitting processes. GDEs offer a cost-effective alternative to traditional planar electrodes, and open new reaction pathways for versatile product generation. For example, GDE’s can improve on the incumbent technologies capable of converting sodium sulfate waste into useful chemicals such as sodium hydroxide and sulfuric acid. Aepnus’ GDEs are poised to revolutionize the recycling of sodium sulfate, the largest waste product of the lithium battery supply chain.The application of these GDE’s can extend into the synthesis of various metal hydroxides and other essential commodity chemicals. Aligning with the principles of circular economy and eco-manufacturing, our project addresses challenges in electrolyzer design, catalyst advancement, and reactor optimization. We underscore the translation from academic research to scalable solutions, integrating our technology seamlessly into existing industrial processes.This presentation will delve into the environmental and operational advantages of Aepnus GDEs, their role in reducing the ecological footprint of chemical manufacturing for the battery industry, and our journey to manufacture chemicals in ways that are circular and carbon neutral. Additionally, we will provide insights into the setbacks of existing electrochemical technologies such as membrane electrolysis and bi-polar electrodialysis (BPED), while demonstrating the real-world applicability of our technology through performance data at lab and pilot-scales.

(Invited) Electrochemical Engineering Approaches for High-Performing Electrosynthesis of Polymer Precursors

The chemical industry accounts for ~5% of the US energy utilization and >30% of the US energy-derived industrial CO2 emissions. Amongst these processes, the production of organic chemical commodities, many of which are used as polymer precursors, account for the majority of the energy utilization (>1200 TBTU/y). The electrification of these processes via the implementation of electro-organic reactions could accelerate the decarbonization of the chemical industry, and bring additional sustainability advantages over their thermo-chemical counterparts. Currently, however, two major challenges prevent the deployment of electro-organic reactions: their low selectivity and their low production rates. To circumvent these barriers, our group deploys electrochemical reaction engineering principles to engineer electrode/electrolyte interfaces and design high-performing electro-organic processes. In this presentation, I will discuss how we implement this approach to understand and improve the performance of electro-organic reactions for the production of large-scale precursors for the production of Nylon 6,6 and polyethylene.The production of Nylon 6,6 involves the step-growth polymerization of 1,6-hexanediamine (HMDA) with adipic acid. HMDA is currently produced by the hydrogenation of adiponitrile (ADN). Here, I will present our insights into the electrohydrodimerization of acrylonitrile (AN) to adiponitrile (ADN). This is one of the largest electro-organic reaction deployed in industry and serves as a model process for the development of practical organic electrochemical processes. Our investigations on ADN uncovered relationships between the microenvironment at and near the electrical double layer (EDL) and reaction performance metrics (i.e., selectivity, efficiency, and productivity). I will discuss general guidelines for electrolyte formulation, dynamic electrochemical operation, the implementation of convective forces to mitigate transport limitations, ultimately leading in the conversion of AN to ADN at Faradaic efficiencies >80% and current densities of 100’s mA/cm2. Our learnings on ADN electrosynthesis helped us to engineer the electrocatalytic hydrogenation of ADN to HMDA, achieving the highest reported selectivity to date for this reaction (>95%). I will also show how similar electrochemical engineering approaches allowed us to elucidate factors that control performance in the electrochemical production of ADN from glutamic acid, an abundant and inexpensive bio-based feedstock, and of ethylene from bio-derived propionic acid. Through our studies, we aim to electrify and bring sustainability to chemical manufacturing, one reaction at a time.

The Diverse Electrochemistry and Photophysics of Pyrrolopyrroles

Pyrrole is among the most popular molecular scaffolds for biology. Tetrapyrroles, such as porphyrins, corrins and their derivatives, are the quintessential redox centers and chromophores exhibiting a wide range of electrochemical and optical characteristics. Similarly, pyrrolopyrroles, built on condensed five-member rings with nitrogens as heteroatoms, offer scaffolds for organic chromophores with diversity of redox and photophysical properties. For example, pyrrolo[3,2-b]pyrroles are stable electron-rich UV absorbers with quadrupole symmetry (Acc. Chem. Res. 2017, 50, 2334-2345). They can act as immensely potent electron donors and attaching electron-accepting moieties to them leads to the emergence of a myriad of optical phenomena, such as excited-state symmetry breaking (Commun. Chem. 2020, 3, 190) and generating white fluorescence by tuning donor-acceptor electronic coupling (Chem. Sci. 2023). Attaching carbonyls to the pyrrolopyrrole rings drastically changes their electronic properties, making them pronouncedly electron deficient and shifting their absorption to the visible spectral region. For example, 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-diones, or diketopyrrolopyrroles (DPPs) for short, are excellent electron acceptors and photooxidants (Adv. Opt. Matter. 2015, 3, 2018-320). Their reduction potentials are susceptible to localized electric fields, which has allowed demonstrating dipole-induced rectification of photoinduced hole transfer (Angew. Chem. Int. Ed. 2018, 57, 12365-12369). This field susceptibility extends to the optical properties of DPPs, providing an extra dimension in their utility for photonics and optoelectronics. DPPs, and pyrrolopyrroles in general, are built on small bicyclic scaffolds, i.e., considerably smaller than those of other multi-pyrrole chromophores. The small size enhances the susceptibility of their redox properties to solvation and makes them attractive photoprobes. Therefore, this class of compounds have become indispensable agents for electrochemical and photonic science and engineering.

Accelerated Development and Optimization of Adiponitrile Production via Kolbe Electrolysis of Biomass-Derived Precursors

Environmental and societal pressures are demanding a transition from fossil-based resources to renewable and sustainable feedstocks for the production of materials. In this context, biomass streams emerge as scalable candidates for creating sustainable chemicals. Electrocatalytic transformation of biomass can facilitate the production of chemicals under mild conditions and can be easily integrated with renewable energy sources. These transformations could lead to the production of sustainable monomers and polymers from biomass, significantly enhancing the sustainability of plastics production. Amongst a large number of plastics manufactured by the chemical industry, Nylon 6,6 is one of the most important fossil-derived polymers for the production of high-performance textiles and structural materials. Central to Nylon 6,6 production is adiponitrile (ADN), predominantly synthesized via energy-intensive thermochemical processes. An alternative route, electrochemical hydrodimerization of acrylonitrile (AN), although successful, still depends on fossil feedstocks. A promising sustainable source for ADN is renewable glutamic acid, derived from hydrolysis of waste proteins.1,2 This process involves transforming glutamic acid to 3-cyanopropanoic acid (CPA) and then to ADN through Kolbe electrolysis, a reaction with a historical background and multiple pathways. Our study utilizes an electrochemical reaction engineering approach to examine the Kolbe electrolysis of CPA to ADN and AN, focusing on a hierarchical research methodology. This approach allowed us to simultaneously accelerate the exploration of numerous reaction parameters while also conducting detailed studies under optimal conditions. This method has enabled us to gain deeper insights into the factors controlling reaction selectivity. We discovered that platinum electrodes favor ADN formation, with selectivity increasing at higher current densities. Optimal CPA concentrations, the presence of larger alkali cations, solvent composition, and controlled pH levels significantly influence ADN production, reducing side reactions such as the oxygen evolution reaction (OER). When using graphite electrodes, an increase in AN production was observed, with the solvent composition playing a crucial role in determining the rate of ADN formation. Our investigation has led to a deeper understanding of the electrochemical conversion of CPA to ADN, revealing key parameters that influence reaction selectivity and rate. The insights obtained from this study are not only pivotal for the specific case of ADN production but also have broader implications for a range of electrochemical decarboxylation reactions. The hierarchical research approach employed here demonstrates its potential for speeding the development of sustainable electrochemical processes. Our insights and methodology used for the electrosynthesis of ADN from biomass-derived feedstocks can be deployed to the deployed to the development of other biomass transformations advancing our ability to produce essential chemicals sustainably.

(Vittorio de Nora Award) When Solid State Semiconductor Physics and Devices Meet Photoelectrochemistry: From Growth and Interfacial Processes to Photovoltaics

I joined the CNRS solid-state physics laboratory near Paris in 1978, to work on the preparation of CdTe solar cells using close space sublimation (CSS) growth process. Thanks to some original discoveries, we were able to achieve a record yield of 10.5% for the time, but this research was gradually abandoned in France and in Europe. Yet it was this method that formed the basis of the technology developed with such success by first solar. So I was on the right track.However, it was in a different direction that I decided to go: semiconductor photoelectrochemistry, a rapidly developing field at the time. Here too, solar energy remained the backdrop, with the field opened up by Honda’s work on the photoelectrolysis of water. I thus began research into the mechanisms of charge transfer at semiconductor-electrolyte interfaces, keeping CdTe as my study material, enabling me to draw on my knowledge of solid-state devices to guide the analysis of its photoelectrochemical behavior in an original way. Our studies have focused on highlighting the energetic changes at interfaces under illumination during charge transfer reactions towards redox species in competition with corrosion reactions. We have demonstrated the role of adsorption and surface chemistry in these phenomena, with the result that photoelectrochemical properties can be optimized. Photoelectrochemistry is once again a highly topical field with artificial photosynthesis.In 1980 I discovered that CdTe layers could be deposited electrochemically in a simple beaker, as theorized by F.A. Kröger, without having to use much heavier vacuum processes.The electrochemical deposition of CdTe immediately became one of the major themes of my research, and remained so until the 2000s. The analysis of deposition mechanisms and their relationships to film properties were the subject of numerous publications and theses, with some outstanding results, in particular the synthesis of a new phase such as CdTe2, the study of as-grown semiconducting properties , the demonstration of epitaxial growth.This work gave rise to two major lines of research with far-reaching consequences. The first concerns the extension of electrochemical synthesis to other compound semiconductors of oxide type, with the discovery of the electrochemical synthesis of ZnO by cathodic reduction in the presence of oxygen, leading to materials of exceptional crystalline quality, suitable for epitaxial deposition. Depending on the experimental conditions, the forms obtained can range from nanocolumns to compact films. These results have opened a new avenue at international level. They led us to introduce them into the photovoltaic field for the formation of TCOs or hybrid matrices for dye cells. The second concerns the electrochemical synthesis of CuInGaSe2 (note CIGS), a ternary semiconductor of major industrial importance to photovoltaics. Initiated in the early 90s, this work involved both fundamental research and the creation of an industrial outlet. It led to the creation of a laboratory dedicated to photovoltaics with EDF in 2002, which succeeded in the creation of a start-up in 2009, NEXCIS, which achieved world-class performance in the field. This adventure has been the subject of a book chapter. Today, it continues with the creation of a new start-up, that I founded in 2021, that is using the electrodeposition technology to manufacture ultra-light, flexible, high-efficiency photovoltaic modules for new applications.This vision of the fundamental and underestimated interest of solution growth methods (electrochemistry or CBD) for the development of high-quality functional materials, particularly for photovoltaic conversion, has guided my entire scientific approach to date. The emergence of halogenated perovskite cells, also prepared in solution, has recently reinforced this approach as a way forward.Selected references:RECOMBINATION AND CHARGE-TRANSFER AT THE ILLUMINATED N-CdTe ELECTROLYTE INTERFACE - SIMPLIFIED KINETIC-MODEL ,LINCOT, D; VEDEL, J, JOURNAL OF ELECTROANALYTICAL CHEMISTRY 220 (1987) 179MECHANISM OF CHEMICAL BATH DEPOSITION OF CADMIUM-SULFIDE THIN-FILMS IN THE AMMONIA-THIOUREA SYSTEM - IN-SITU KINETIC-STUDY AND MODELIZATION, ORTEGABORGES, R; LINCOT, D, JOURNAL OF THE ELECTROCHEMICAL SOCIETY 140 (1993)3464.SOLAR-CELLS WITH IMPROVED EFFICIENCY BASED ON ELECTRODEPOSITED COPPER INDIUM DISELENIDE THIN-FILMS, GUILLEMOLES, JF; COWACHE, P; MASSACCESSI, S; THOUIN, L; SANCHEZ, S; LINCOT, D; VEDEL, J., Advanced Materials 6 (1994)379Mechanistic study of cathodic electrodeposition of zinc oxide and zinc hydroxychloride films from oxygenated aqueous zinc chloride solutions, Peulon, S; Lincot, D , JOURNAL OF THE ELECTROCHEMICAL SOCIETY 145 (1998)864Solution growth of functional zinc oxide films and nanostructures, Lincot, D., MRS BULLETIN 35(2010) 778From the Lab to Scaling-up Thin Film Solar Absorbers. Hariklia Deligianni, Lubomyr T. Roamnkiw, Daniel Lincot, Pierre-Philippe Grand. Book Chapter in Advances in Electrochemical Science and Engineering,XVIII (2018)

(Industrial Electrochemistry and Electrochemical Engineering Division H. H. Dow Memorial Student Achievement Award) Tailoring Electrode-Electrolyte Interfaces through Non-Covalent Interactions for Electrochemical Energy Storage and Conversion

Li-ion batteries and fuel cells play essential roles in electrifying transportation. Central to the electrochemical systems is the electrode-electrolyte interface, where (electro)chemical surface reactions or intercalation occur, and its thermodynamic and kinetic properties determine the energy density, power density, and lifetime of the electrochemical devices. However, the molecular structures at the electrical double layer and reaction mechanisms remain poorly understood, hindering the rational material design for more efficient electrochemical devices. This talk focuses on the mechanisms of (electro)chemical reactions and charges transfer kinetics at the electrode-electrolyte interface, providing design principles based on non-covalent interactions in electrolytes.First, an in situ Fourier-transform infrared spectroscopy (FTIR) method was developed for Li-ion batteries, which revealed unique evidence for dehydrogenation of carbonate electrolytes on Ni-rich lithium nickel, manganese and cobalt oxides (NMC), accounting for interface impedance build-up and battery capacity fading. Based on the proposed mechanism, strategies on suppressing electrode and electrolyte reactivity were demonstrated to improve battery cycling. Next, the kinetic mechanism for ion intercalation at the electrode-electrolyte interface will be discussed. Li-ion concentration-dependent intercalation kinetics was demonstrated from charge-adjusted electrochemical experiments and fit into a coupled ion-electron transfer mechanism, which governed the current-dependent maximum capacity and power density of intercalation batteries. Finally, for electrocatalytic reactions central to fuel cell technologies, we demonstrated tuning interfacial hydrogen bonding through protic ionic liquids with different acid dissociation constants and organic solvents with different donor numbers to tailor oxygen-reduction reaction (ORR) and hydrogen evolution reaction (HER). Strengthening hydrogen bonding between ORR products and ionic liquids, or between interfacial water molecules facilitated proton-coupled electron transfer kinetics, revealed by in situ surface-enhanced infrared absorption spectroscopy and density functional theory (DFT) calculations. The study can pave the way for the electrolyte and electrode design of electrochemical storage devices with improved energy and power density and cycle life.

Quantifying Volume Change in Porous Electrodes via the Multi-Species, Multi-Reaction Model

Automotive manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost; and active material volume change is one of the more complex aspects that needs to be considered during this process. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods, the need for coupled electrochemical/mechanical models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary[1-9]. In this study[10], we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge[11-16] and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions. References T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014).T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, Ecs Transactions, 72, 11 (2016).T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017).D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019).D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020).T. R. Garrick, J. Gao, X. Yang and B. Koch, J Electrochem. Soc., 168 (1) 010530 (2021)D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez and J. W. Weidner, J Electrochem Soc, 170, 100513 (2023).T. R. Garrick, M. A. Fernandez, M. Verbrugge, C. Labaza, R. Mollah, B. J. Koch, M. Jones, J. Gao, X. Gao and N. Irish, J. Electrochem. Soc., 170 060548 (2023)M. Verbrugge, D. Baker and X. Xiao, J Electrochem Soc, 163, A262 (2016).M. Verbrugge, D. Baker, B. Koch, X. Xiao and W. Gu, J Electrochem Soc, 164, E3243 (2017).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 165, A3952 (2018).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 167, 013504 (2019).D. R. Baker, M. W. Verbrugge and W. Gu, J Electrochem Soc, 166, A521 (2019).M. W. Verbrugge, X. Xiao and D. R. Baker, J Electrochem Soc, 167, 080523 (2020).