Energy Sciences Research Articles

Recent Advances in Photocatalytic Nitrogen Fixation Based on Two‐Dimensional Materials

AbstractUtilizing solar energy for photocatalytic nitrogen fixation has been extensively regarded as a promising avenue towards renewable nitrogen energy production. 2D materials, renowned for their unique structures and properties, have sparked remarkable advancements in the realm of energy and environment sciences. In this review, we delve into the recent advancements pertaining to 2D materials for solar‐driven photocatalytic nitrogen fixation. This encompasses a diverse array of materials, including metal carbides/nitrides (MXenes), transition metal dichalcogenides (TMDs or TMDCs), graphitized carbon nitride (g‐C3N4), metal‐organic frameworks (MOFs), covalent organic frameworks (COFs), and covalent triazine‐based frameworks (CTFs). We offer a fundamental understanding of the functionalities exhibited by various 2D materials in enhancing photocatalytic nitrogen fixation activity. The photocatalytic properties of these 2D materials are meticulously examined from multiple perspectives, including visible light absorption capabilities, charge transfer within the energy band, and reaction mechanisms. Finally, we present an in‐depth discussion on the existing challenges and prospects surrounding the application of 2D materials in photocatalytic nitrogen fixation.

Effectively Sieving Alkali Metal Ions Using Functionalized Graphene Oxide Membranes by Exploiting Water-Repellent Interactions.

Sieving membranes capable of discerning different alkali metal ions are important for many technologies, such as energy, environment, and life science. Recently, two-dimensional (2D) materials have been extensively explored for the creation of sieving membranes with angstrom-scale channels. However, because of the same charge and similar hydrated sizes, mostly laminated membranes typically show low selectivity (<10). Herein, we report a facile and scalable method for functionalizing graphene oxide (GO) laminates by dually grafting cations and water-repellent dimethylsiloxane (DMDMS) molecules to achieve high selectivities of ∼50 and ∼20 toward the transport of Cs+/Li+ and K+/Li+ ion pairs, surpassing many of the state-of-the-art laminated membranes. The enhanced selectivity for alkali metal ions can be credited to a dual impact: (i) strong hydrophobic interactions between the incident cations' hydration shells and the water-repellent DMDMS; (ii) the efficient screening of electrostatic interactions that hamper selectivity.

Valence electron matching law for MXene-based single-atom catalysts

Single-atom catalysts (SACs) have attracted considerable interest in the fields of energy and environmental science due to their adjustable catalytic activity. In this study, we investigated the matching of valence electron numbers between single atoms and adsorbed intermediates (O, N, C, and H) in MXene-anchored SACs (M-Ti2C/M-Ti2CO2). The density functional theory results demonstrated that the sum of the valence electron number (VM) of the interface-doped metal and the valence electron number (VA) of the adsorbed intermediates in M-Ti2C followed the 10-valence electron matching law. Furthermore, based on the 10-valence electron matching law, we deduced that the sum of the valence electron number (k) and VM for the molecular adsorption intermediate interactions in M-Ti2CO2 adhered to the 11-valence electron matching law. Electrostatic repulsion between the interface electrons in M-Ti2CO2 and H2O weakened the adsorption of intermediates. Furthermore, we applied the 11-valence electron matching law to guide the design of catalysts for nitrogen reduction reaction, specifically for N2→NNH conversion, in the M-Ti2CO2 structure. The sure independence screening and sparsifying operator algorithm was used to fit a simple three-dimensional descriptor of the adsorbate (R2 up to 0.970) for catalyst design. Our study introduced a valence electron matching principle between doped metals (single atoms) and adsorbed intermediates (atomic and molecular) for MXene-based catalysts, providing new insights into the design of high-performance SACs.

Preface: 7th Astechnova International Energy Conference (ASTECHNOVA 2023)

Abstract Astechnova International Energy Conference (ASTECHNOVA) is an international conference that is annually organized by the Department of Nuclear Engineering and Engineering Physics, Universitas Gadjah Mada, Indonesia. This 7th ASTECHNOVA was held on October 4-5, 2023. This conference provides an ideal platform for researchers, academicians, engineers, politicians, economists, energy enthusiasts, energy planners, and energy analysts, to share the recent research and development in the energy science discipline from various perspectives: New and Renewable Energies, Nuclear Technology, Energy Securities, Energy Efficiency, and Urban Infrastructure and Utilities The conference was attended by approximately 300 participants from various universities and institutions in Kiribati, India, Japan, South Korea, Malaysia, Thailand, Canada, the United States of America, Singapore, and Indonesia. The panel session of this conference includes one (1) keynote lecture and six (6) invited talks by the panel speakers from across the globe. As for the parallel session, oral presentations were delivered by the authors who submitted their research. In total, the ASTECHNOVA 2023 organizer accepted 64 paper submissions after being reviewed by distinguished experts in the field. The reviewing process has considerably reduced the number of published papers, but it also has raised the proceedings’ quality. Finally, we would like to thank all the participants, authors, panel speakers, reviewers, panel session moderators, parallel session chairs, steering committee, organizing committee, technical coordinators, and all other supporting staff for their tremendous support during this conference. Astechnova 2023 Editorial Team List of Committees are available in this Pdf.

Locally Adaptive Shrinkage Priors for Trends and Breaks in Count Time Series

Non-stationary count time series characterized by features such as abrupt changes and fluctuations about the trend arise in many scientific domains including biophysics, ecology, energy, epidemiology, and social science domains. Current approaches for integer-valued time series lack the flexibility to capture local transient features while more flexible models for continuous data types are inadequate for universal applications to integer-valued responses such as settings with small counts. We present a modeling framework, the negative binomial Bayesian trend filter (NB-BTF), that offers an adaptive model-based solution to capturing multiscale features with valid integer-valued inference for trend filtering. The framework is a hierarchical Bayesian model with a dynamic global-local shrinkage process. The flexibility of the global-local process allows for the necessary local regularization while the temporal dependence induces a locally smooth trend. In simulation, the NB-BTF outperforms a number of alternative trend filtering methods. Then, we demonstrate the method on weekly power outage frequency in Massachusetts townships. Power outage frequency is characterized by a persistent low level trend with occasional spikes. These illustrations show the estimation of a smooth, non-stationary trend with adequate uncertainty quantification.

Semiconducting Heusler Compounds beyond the Slater-Pauling Rule

Heusler compounds with semiconducting properties represent an important class of functional materials. Usually, research on these systems is guided by simple electron-counting rules, such as the Slater-Pauling principle. Here, we report on the discovery of Heusler-type semiconductors, significantly deviating from the Slater-Pauling rule. We theoretically predict the occurrence of nonmagnetic semiconducting ground states in various highly off-stoichiometric full-Heusler alloys, where self-substitution leads to a band-gap opening. This unexpected trend is confirmed experimentally by thermoelectric transport measurements on a multitude of Fe2−2xV1−xAl1+3x samples with up to 20% substitution of Fe and V atoms. The band-gap opening leads to an exceptionally large Seebeck coefficient in p-type Fe2VAl thermoelectrics, previously limited by bipolar conduction and low-density-of-states effective mass. Consequently, our work presents a paradigm to tune the band gap of Heusler compounds by self-substitution and introduces a hitherto unexplored class of semiconductors with exceptional thermoelectric properties, offering significant potential for advancements in energy science and sustainable-energy technologies. Published by the American Physical Society 2024

6th International conference on energy, materials and environmental science: enhancing thermal properties of wood–plastic composites through incorporation of phase change materials: a short review

6th International conference on energy, materials and environmental science: enhancing thermal properties of wood–plastic composites through incorporation of phase change materials: a short review

Recent Advances in Piezoelectric Coupled with Photocatalytic Reaction System: Synergistic Mechanism, Enhancement Factors, and Application.

The field of photocatalysis has demonstrated numerous advantages in the domains of environmental protection, energy, and materials science. However, conventional modification methods fail to simultaneously enhance carrier separation efficiency, redox capacity, and visible light absorption solely through light activation due to the intrinsic band structure limitations of photocatalysts. In addition to modification methods, the introduction of an external field, such as a piezoelectric field, can effectively address deficiencies in each step of the photocatalytic process and enhance the overall performance. The assistance of a piezoelectric field overcomes the limitations inherent in traditional photocatalytic systems. Hence, this review provides a comprehensive overview of recent advancements in piezoelectric-assisted photocatalysis and thoroughly investigates the interaction between the alternating piezoelectric field and photocatalytic processes. Various ideas for synergistic enhancement of the piezoelectric and photocatalytic properties are also explored. This multifield catalytic system shows remarkable performance in stability, pollutant degradation, and energy conversion, distinguishing it from single catalytic systems. Finally, an in-depth analysis is conducted to address the challenges and prospects associated with piezoelectric photocatalysis technology.

Constructing covalent organic frameworks with dense thiophene S sites for effective iodine capture

Developing versatile sorption materials for radionuclide capture (e.g. iodine) is critical for nuclear energy and environmental science. Covalent organic frameworks (COFs) have recently become a new platform for developing sorption materials because of their high surface area and functionalised skeleton structure. Herein, two types of COF materials containing thiophene were designed as iodine sorbents and synthesised via a Schiff base reaction of benzo[1,2-b:3,4-b’:5,6-b’’]trithiophene-2,5,8-tricarbaldehyde, benzidine (DADP) and p-phenylenediamine (DAB): DADP-COF and DAB-COF. DAB-COF exhibits a unique granular-rod-like morphology and has a higher surface area (1775 m2/g) than DADP-COF (1140 m2/g), which is clearly beneficial for the physical adsorption of iodine. Meanwhile, the COF backbone is rich in N and S sites, which are advantageous for the chemical adsorption of iodine. These two features make the two prepared COFs ideal iodine sorption materials. DAB-COF demonstrates an excellent gaseous iodine adsorption capacity of 4.2 g/g, ranking it as one of the most effective iodine sorption materials, while DADP-COF exhibits a good adsorption capacity of over 235 mg/g for iodine in cyclohexane solutions. Density functional theory calculations prove that imine N and thiophene S serve as active sites during the iodine adsorption. DAB-COF exposes more active sites because of its higher surface area, leading to a higher iodine adsorption capacity than DADP-COF. The results of this study indicate that introducing thiophene to COFs improves sorption efficacy for sorption applications in general and particularly paves the way for developing stable and effective COF sorbents for iodine capture from various environments.

Photocatalytic Reforming of Ethanol in the Liquid Phase Using a Ternary Composite of Rh/TiO2/g-C3N4 as a Catalyst.

Photocatalytic reforming of ethanol provides an effective way to produce hydrogen energy using natural and nontoxic ethanol as raw material. Developing highly efficient catalysts is central to this field. Although traditional semiconductor/metal heterostructures (e.g., Rh/TiO2) can result in relatively high catalyst performance by promoting the separation of photoinduced hot carriers, it will still be highly promising to further improve the catalytic performance via a cost-effective and convenient method. In this study, we developed a highly efficient photocatalyst for ethanol reformation by preparing a ternary composite structure of Rh/TiO2/g-C3N4. Hydrogen is the main product, and the reaction rate could reach up to 27.5 mmol g-1 h-1, which is ∼1.41-fold higher than that of Rh/TiO2. The catalytic performance here is highly dependent on the wavelength of the light illumination. Moreover, the photocatalytic reforming of ethanol and production of hydrogen were also dependent on the Rh loading and g-C3N4:TiO2 ratio in Rh/TiO2/g-C3N4 composites as well as the ethanol content in the reaction system. The mechanism of the enhanced hydrogen production in Rh/TiO2/g-C3N4 is determined as the improvement in the separation of photoinduced hot carriers. This work provides an effective photocatalyst for ethanol reforming, largely expanding its application in the field of renewable energy and interface science.

Advances in the Fabrication, Properties, and Applications of Electrospun PEDOT-Based Conductive Nanofibers.

The production of nanofibers has become a significant area of research due to their unique properties and diverse applications in various fields, such as biomedicine, textiles, energy, and environmental science. Electrospinning, a versatile and scalable technique, has gained considerable attention for its ability to fabricate nanofibers with tailored properties. Among the wide array of conductive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) has emerged as a promising material due to its exceptional conductivity, environmental stability, and ease of synthesis. The electrospinning of PEDOT-based nanofibers offers tunable electrical and optical properties, making them suitable for applications in organic electronics, energy storage, biomedicine, and wearable technology. This review, with its comprehensive exploration of the fabrication, properties, and applications of PEDOT nanofibers produced via electrospinning, provides a wealth of knowledge and insights into leveraging the full potential of PEDOT nanofibers in next-generation electronic and functional devices by examining recent advancements in the synthesis, functionalization, and post-treatment methods of PEDOT nanofibers. Furthermore, the review identifies current challenges, future directions, and potential strategies to address scalability, reproducibility, stability, and integration into practical devices, offering a comprehensive resource on conductive nanofibers.

Energy storage chemistry: Atomic and electronic fundamental understanding insights for high-performance supercapacitors

The scarcity of fuels, high pollution levels, climate change, and other major environmental issues are critical challenges that modern societies are facing, mostly originating from fossil fuels-based economies. These challenges can be addressed by developing green, eco-friendly, inexpensive energy sources and energy storage devices. Electrochemical energy storage materials possess high capacitance and superior power density. To engineer highly efficient next-generation electrochemical energy storage devices, the mechanisms of electrochemical reactions and redox behavior must be probed in operational environments. They can be studied by investigating atomic and electronic structures using in situ x-ray absorption spectroscopy (XAS) analysis. Such a technique has attracted substantial research and development interest in the field of energy science for over a decade. The mechanisms of charge/discharge, carrier transport, and ion intercalation/deintercalation can be elucidated. Supercapacitors generally store energy by two specific mechanisms—pseudocapacitance and electrochemical double-layer capacitance. In situ XAS is a powerful tool for probing and understanding these mechanisms. In this Review, both soft and hard x rays are used for the in situ XAS analysis of various representative electrochemical energy storage systems. This Review also showcases some of the highly efficient energy and power density candidates. Furthermore, the importance of synchrotron-based x-ray spectroscopy characterization techniques is enlightened. The impact of the electronic structure, local atomic structure, and electronically active elements/sites of the typical electrochemical energy storage candidates in operational conditions is elucidated. Regarding electrochemical energy storage mechanisms in their respective working environments, the unknown valence states and reversible/irreversible nature of elements, local hybridization, delocalized d-electrons spin states, participation of coordination shells, disorder, and faradaic/non-faradaic behavior are thoroughly discussed. Finally, the future direction of in situ XAS analysis combined with spatial chemical mapping from operando scanning transmission x-ray microscopy and other emerging characterization techniques is presented and discussed.

Tackling gender disparities in energy research: a diagnostic tool for equality in research centres

BackgroundIn a case study in Spain, the unequal proportion of men and women in a research organization in the energy sector is severe, and long-established dynamics that might determine differences in access to leadership positions and inequalities in research careers are evident. The gender gap in historically masculinized fields, such as energy engineering reflects more than simply the differences in male and female values and personalities. This study seeks to explore the gender gap in energy research centres and to identify barriers that potentially hinder the research careers of women. It proposes the development of a diagnostic tool, based upon indicators, to monitor and evaluate gender roles and inequalities in the management of research centres for identifying and addressing the dynamics and obstacles that hinder women's progress in the energy sector and their potential contribution to the field. This participatory multicriteria-based tool prioritizes the proposed indicators by their influence and importance in the context of energy research and applies it to the monitoring of a specific Spanish energy research centre.ResultsThe results are threefold: (i) the methodology is adaptable to different research centres; (ii) the analysis of indicators’ prioritization could lead to recommendations that should be addressed first; (iii) the diagnostic tool used in this in-depth case study of an energy research centre in Spain allowed results to be achieved in terms of gender dynamics. Two indicators stand out as the most relevant in our analysis: gender diversity in leadership positions and uncomplicated application of work–life balance measures. In this case study, the measurement of the first indicator has drawn unsatisfactory results, and the research of the latter is considered still insufficient. In conclusion, this difference becomes a vicious or negative circle for attracting and retaining more women to the research centre. Despite these results, no gender gap seems to be recognized and thus, no measures are being taken to improve the situation.ConclusionsComprehensive data and contextualized monitoring are necessary to effectively study and enhance the presence and participation of women in the energy science sector. This approach, combining quantitative and qualitative techniques, is suitable for any research centre that would like to monitor its gender gap, identify potential sources of inequity and address them.

Unlocking the photothermal conversion capacity of lignin and lignin-derived materials

Lignin is the most prevalent polyphenolic organic solid waste generated by the pulping and biorefining industries. It confers upon woody biomass a remarkable combination of physical, chemical, and biological resilience, while simultaneously exhibiting considerable potential for photothermal conversion. In recent years, the utilization of technical lignin and lignin by-products to develop photothermal materials has emerged as a research hotspot. This review introduces the industrial separation processes and characterization of different types of lignin, highlighting the chemical structures of lignin and its derivatives linked to their photothermal conversion mechanisms. The evaluation pathways for photothermal conversion are summarized and critically assessed, as guided by mathematical descriptions of best practices in lignin-derived materials. This review covers and reflects on recent and emerging advances in materials and energy sciences that demonstrate how lignin can be utilized to maximize solar-to-thermal conversion and versatility in desalination, electricity generation, therapy, and intelligent and environmentally friendly building materials. Finally, the challenges and proposed future directions for the development of lignin-derived photothermal materials are identified with the objective of challenging the prevailing notion that lignin is merely an organic solid waste.

Pressure Characteristics and Secondary Ignition Effects of Gas Produced in RDE Using Lignite and Anthracite/CH4 Fuel.

This study aims to address the energy efficiency release and environmental impact of coal dust in rotating detonation engines (RDEs) by monitoring the detonation characteristics of lignite and anthracite in methane gas-solid mixtures using high-precision sensor technology. Experimental results indicate that the peak detonation pressure of anthracite is 1.4% higher than that of lignite, and its detonation wave propagation speed is at least 5.5% faster, suggesting that anthracite exhibits more stable and efficient fuel energy release characteristics during detonation. Additionally, the sensor technology enabled detailed recording of pressure fluctuations and gas composition changes during the detonation process, providing accurate data for assessing and controlling emissions of harmful gases such as carbon monoxide and carbon dioxide. These data are crucial for designing more efficient and environmentally friendly coal dust detonation systems, enhancing mine safety and environmental protection. The outcomes of this research not only advance technological progress in the field of energy science but also address efficiency and environmental issues in industrial applications, offering significant support for achieving safer and more sustainable energy production methods.

(Battery Student Slam 8 Award Winner) A Simple and Fast Method to Assemble Flexible and Stable Quasi-Solid-State Zn Ion Pouch Cell

Aqueous zinc-ion batteries (AZIBs) have been investigated intensively as effective energy storage devices that are environmentally friendly, safe, and have a lower cost than current Li-ion batteries.[1-5] Being outstandingly safe due to usage of non-organic electrolyte, AZIBs could also be used as power supply for wearable electronics. This also put high standard requirements in terms of flexibility, stability and electrochemical performance to AZIBs. On the other hand, the general challenges, such as the formation of the dendrites on the Zn anodes, hydrogen evolution and side reactions, have been obstructing the practical application of AZIBs. In this presentation, a simple method to assemble quasi-solid-state Zn ion pouch cell with excellent mechanical performance, flexibility and electrochemical performance was developed, combining in-situ electrodeposition of MnO2 cathode and aramid nano fiber-based hydrogel with Zn plate as anode. In-situ and cycling measurements of the electrodeposition of MnO2 on carbon nanotube mat shows excellent capacitance and superior cycling stability. In addition, Kevlar derivatized aramid nanofiber-based hydrogel shows extremely strong strength when combined with polyvinyl alcohol, which prolonged the lifetime of the cell by preventing Zn dendrite growth largely.[5,6] Moreover, the method to assemble the AZIBs pouch cell enables us to optimize the process, decrease the steps, and save time effectively by taking advantage of hydrogel formation stage and avoiding conventional verbose slurry-casting-drying steps. This work paves an efficient path to assemble flexible and stable AZIBs pouch cells with high capacity and cycling stability.[1] Tang, Boya, et al. "Issues and opportunities facing aqueous zinc-ion batteries." Energy & Environmental Science 12.11 (2019): 3288-3304.[2] Li, Chang, et al. "Toward practical aqueous zinc-ion batteries for electrochemical energy storage." Joule 6.8 (2022): 1733-1738.[3] Yu, Feng, et al. "An aqueous rechargeable zinc-ion battery on basis of an organic pigment." Rare Metals 41.7 (2022): 2230-2236.[4] Lin, Yuexing, et al. "Dendrite-free Zn anode enabled by anionic surfactant-induced horizontal growth for highly-stable aqueous Zn-ion pouch cells." Energy & Environmental Science 16.2 (2023): 687-697.[5] Wang, Peng, and Petru Andrei. "High Performance Separator and Hydrogel Based on Aramid Fibers for Zn Ion Batteries." Electrochemical Society Meeting s 242. No. 4. The Electrochemical Society, Inc., 2022.[6] Xu, Lizhi, et al. "Water‐rich biomimetic composites with abiotic self‐organizing nanofiber network." Advanced Materials 30.1 (2018): 1703343.

(Invited) Sub-Particle-Resolution Microscopy Reveals Inter-Facet Junction Effects on Particulate Photoelectrodes

This presentation will describe our recent work in using single-particle/single-molecule imaging approaches to study photoelectrocatalytic properties of particulate semiconductor photocatalysts, important for many solar energy conversion technologies. In anisotropically shaped photocatalyst particles, the different constituent facets differ in their electronic and thus photoelectrocatalytic properties, and between different facets they may form inter-facet junctions at their adjoining edges, analogous to lateral two-dimensional (2D) heterojunctions or pseudo-2D junctions made of few-layer 2D materials. Using subfacet-level multimodal functional imaging, we uncover inter-facet junction effects on anisotropically shaped bismuth vanadate (BiVO4) particles and identify the characteristics of near-edge transition zones on the particle surface, which underpin the whole-particle photoelectrochemistry. The imaging tools, the analytical framework and the inter-facet junction concept pave new avenues towards understanding, predicting and engineering (opto)electronic and photoelectrochemical properties of faceted semiconducting materials, with broad implications in energy science and semiconductor technology.

Atmospheric Pressure Plasma Jet Synthesis and Characterization of Copper-Silver Bimetallic Materials as Electrocatalysts for CO2 Reduction

Copper-silver (Cu-Ag) bimetallics and alloys are attractive due to their enhanced performance compared to their parent metals in various fields including electronics, batteries, biomedicine, solar technology, energy storage, and catalysis.[1] Existing methods for synthesizing Cu-Ag bimetallics suffer from major drawbacks such as intense temperature and pressure conditions, pre and post-treatment processes, and multiple time-consuming steps.[2, 3]In this work, Cu-Ag bimetallic films were synthesized under various ratios for the first time using a newly developed Atmospheric Pressure Plasma Jet (APPJ) system. Synthesis was done in a single step, in under 15 minutes. The samples exhibited strong adhesion onto various substrates such as glass and glassy carbon. This direct-deposition technique requires low power input (<50 W) without the need for any pre- or post-treatment processes and with little to no waste. This contrasts with wet chemistry, where deposition normally takes 12-24 hours followed by thermal processes that produce several waste products.[4] Considering the high melting points (MP) of pure Cu and Ag (MP of Cu is ca. 1,085 °C and MP of Ag is ca. 962 °C), and the fact that they are immiscible, the formation of Cu-Ag alloys usually requires a high amount of energy under intense conditions.[5]These Cu-Ag films were characterized via cyclic voltammetry (CV), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Here, we demonstrate that by only mixing low-concentration metal salt solutions and using a neutral gas (helium), we can readily synthesize metal alloys while controlling their thickness, shape, composition, and metal ratios. From an electrochemical point of view, APPJ drives the reduction of metal cations from the presence of free electrons. This suggests the presence of a medium that is considered either as an electrode, due to the presence of electrons, or as an electrolyte, due to their electrical conduction.[6]These plasma-synthesized materials were tested as electrocatalysts for reducing atmospheric carbon dioxide (CO2) under various potentials. The performance of these catalysts was assessed via electrochemical surface area (ECSA), electrochemical impedance spectroscopy (EIS), and pulse voltammetry techniques. Copper is the only heterogeneous catalyst that converts CO2 into valuable chemicals, such as hydrocarbons, aldehydes, and alcohols.[7] Interestingly, we illustrate that the addition of silver improves the catalytic activity of copper toward CO2 reduction under low potentials. This is a desirable property given the anticipated transition to green energy. References Tantawy, H.R., et al., Novel synthesis of bimetallic Ag-Cu nanocatalysts for rapid oxidative and reductive degradation of anionic and cationic dyes. Applied Surface Science Advances, 2021. 3: p. 100056. Zhang, X., et al., Microstructures and properties of 40Cu/Ag (Invar) composites fabricated by powder metallurgy and subsequent thermo-mechanical treatment. Metallurgical and Materials Transactions A, 2018. 49: p. 1869-1878. Rajashekhar, B., et al., Electro co-deposition of copper-silver nanocrystallite alloy cluster: A way for tunable SERS substrate development. Materials Letters: X, 2022. 15: p. 100157. Jie, S., et al., Preparation of copper–silver alloy with different morphologies by a electrodeposition method in 1-butyl-3-methylimidazolium chloride ionic liquid. Bulletin of Materials Science, 2019. 42: p. 1-4. Banhart, J., et al., Electronic properties of single-phased metastable Ag-Cu alloys. Physical Review B, 1992. 46(16): p. 9968. Rumbach, P., et al., The solvation of electrons by an atmospheric-pressure plasma. Nature communications, 2015. 6(1): p. 7248. Kuhl, K.P., et al., New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces. Energy & Environmental Science, 2012. 5(5): p. 7050-7059.

(Invited) Atomically Dispersed Metal Electrocatalysts for CO2 to CO Conversion: From Single to Dual Metal Sites

Carbon-supported nitrogen-coordinated single-metal site catalysts (i.e., M−N−C, M: Fe, Co, or Ni) are active for the electrochemical CO2 reduction reaction (CO2RR) to CO.(1) We comprehensively engineered FeN4 and NiNx sites for electrochemical CO2 reduction to CO considering the particle sizes of the catalysts, metal content, and the M−N (M: Fe or Ni) bond structures.(2, 3)The unique M-N-C model allows us to elucidate each factor′s role exclusively regarding the promotion of CO2 reduction.(4)Optimal particle sizes and Fe content provide favorable external factors to improve mass activity. Structural changes of M−N bonds controlled by thermal activation temperatures can intrinsically enhance CO selectivity and kinetic activity. Notably, the NiN3 active sites with optimal local structures formed at higher temperatures (e.g., 1200 °C) are intrinsically more active and CO-selective than NiN4, providing a new opportunity to design a highly active catalyst via populating NiN3 sites with increased density. Further improving their intrinsic activity and selectivity by tuning their N−M bond structures and coordination is limited. We further expand the coordination environments of M−N−C catalysts by designing dual-metal active sites.(5)The Ni-Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N-coordinated dual-metal site configurations are 2N-bridged (Fe-Ni)N6, in which FeN4 and NiN4 moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual-metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single-metal sites (FeN4 or NiN4) with improved intrinsic catalytic activity and selectivity.References Pan F, Zhang H, Liu K, Cullen D, More K, Wang M, et al. Unveiling Active Sites of CO2 Reduction on Nitrogen-Coordinated and Atomically Dispersed Iron and Cobalt Catalysts. ACS Catalysis. 2018;8(4):3116-22.Li Y, Adli NM, Shan W, Wang M, Zachman MJ, Hwang S, et al. Atomically dispersed single Ni site catalysts for high-efficiency CO2 electroreduction at industrial-level current densities. Energy & Environmental Science. 2022;15(5):2108-19.Mohd Adli N, Shan W, Hwang S, Samarakoon W, Karakalos S, Li Y, et al. Engineering Atomically Dispersed FeN4 Active Sites for CO2 Electroreduction. Angewandte Chemie International Edition. 2021;60(2):1022-32.Li J, Zhang H, Samarakoon W, Shan W, Cullen DA, Karakalos S, et al. Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction. Angewandte Chemie International Edition. 2019;58(52):18971-80.Li Y, Shan W, Zachman MJ, Wang M, Hwang S, Tabassum H, et al. Atomically Dispersed Dual-Metal Site Catalysts for Enhanced CO2 Reduction: Mechanistic Insight into Active Site Structures. Angewandte Chemie International Edition. 2022;61(28):e202205632.

Rational Comparison of Anode Material Properties for Anion Exchange Membrane Water Electrolysis

Due to the increasing need for sustainable energy, the hydrogen (H2) economy is a topic of interest where H2 is used for energy storage and as a fuel [1]. In this regard, the utilization of hydrogen as a promising energy source for achieving global decarbonization goals has led to the exploration of water electrolysis (WE) as a viable route for producing green hydrogen [2,3]. Although proton exchange membrane water electrolysis (PEMWE) is established, they suffer from the reliance on expensive noble metals as catalysts. In contrast, recently, anion exchange membrane water electrolysis (AEMWE) is emerging as a low-cost alternative solution that combines the strengths of both alkaline, WE (low capital cost and use of liquid electrolyte), and PEMWE (low ohmic resistance and high gas purity) where cost-effective transition metal oxides can be used [4-5].Among various materials that are being investigated as AEM anodes, Ni-based systems show high promises. However, a rational comparison between different Ni-based benchmarks as AEM anodes under different stages of electrode production is still lacking. Such a comparison would provide insight into the material properties that are relevant for optimization in each stage thereby producing highly performing catalysts. To achieve this, these materials have to be processed under comparable conditions during the electrode fabrication to draw meaningful correlations between the performance and influencing parameters.Herein, we developed a protocol for rationally comparing different commercial benchmark anode materials in AEMWE. The aim is to understand material properties that influence the final catalyst performance and further enhance their catalytic activity by fine-tuning pivotal material properties. We selected Ni-Co-O, Ni-Fe-O, and Ni-Co-O doped by Fe as potential anode materials for AEMWE and performed a systematic evaluation and comparison of the properties in powder, ink, and electrode layer stages.After the initial characterization of the powders by complimentary techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), we developed ink formulations from each material. The stability of dispersions in various solvents was assessed using Hanson Solubility Parameters extracted from Analytical Centrifugation (AC) data [6]. AC in conjunction with own developed algorithms were then used to represent long-term stability data as transmittograms. During the ink development, particular care was taken to use solvent matrices that lead to comparable particle size distributions within the materials library together with constant catalyst to binder ratio and ink processing (e.g., ultrasonication) to assure the properties of each material to be the only free parameter in both ink formulation and electrode development. In the subsequent step, electrode layers from each material were obtained by spray deposition with defined deposition parameters (substrate temperature, ink flow and nozzle to substrate distance) that enabled the achievement of comparable electrode layers. These layers were characterized by atomic force microscopy and N2 sorption for understanding the microstructure and specific surface area of each electrode which was used for normalizing the electrochemical data. Specifically, an own developed AFM-based multi-stage data quantification was applied for evaluating the microstructure on larger scales [7]. Finally, the electrochemical performance of these materials as anodes in AEMWE were tested and correlated with the inherent material properties as well as ink and electrode layer characteristics.This work sheds light on a systematic workflow for characterizing AEMWE anode materials at different stages which provides a comprehensive picture about the underlying property-performance relationship. The developed coherent workflow can be expanded to other materials in AEMWE. Staffell, Iain, et al. "The role of hydrogen and fuel cells in the global energy system." Energy & Environmental Science 12.2 (2019): 463-491.Kusoglu, A., Chalkboard 1-the many colors of hydrogen. The Electrochemical Society Interface, 2021. 30(4): p. 44.Harkema, D., G. Palasantzas, and J. Miocic, Hydorgen in the European energy transition: Where will it come from? 2022.Miller, H.A., et al., Green hydrogen from anion exchange membrane water electrolysis: a review of recent developments in critical materials and operating conditions. Sustainable Energy & Fuels, 2020. 4(5): p. 2114-2133.Santoro, C., et al., What is Next in Anion‐Exchange Membrane Water Electrolyzers? Bottlenecks, Benefits, and Future. ChemSusChem, 2022. 15(8): p. e202200027.Bapat, S., et al., Towards a framework for evaluating and reporting Hansen solubility parameters: applications to particle dispersions. Nanoscale Advances, 2021. 3(15): p.4400-4410.Jain, A., et al., "Small-Area Observations to Insight: Surface-Feature-Extrapolation of Anodes via Multistage Data Quantification. " Under review, ChemCatChem