Catalytic Process Research Articles

Immobilization of silver-loaded graphene oxide (Ag-GO) on canvas fabric support for catalytic conversion of 4 nitrophenol.

Due to the rising human population and industrialization, harmful chemical compounds such as 4-nitrophenol (4-NP) and various dyes are increasingly released into the environment, resulting in water pollution. It is essential to convert these harmful chemicals into harmless compounds to mitigate this pollution. This research focuses on synthesizing a novel heterogeneous catalyst using modified canvas fabric (CF) decorated with silver metal nanoparticles on graphene oxide nanosheets (Ag-GO/CF). The process involves coating the fabrics (CF) with graphene oxide (GO) nanosheets through sonication. Subsequently, silver nanoparticles are deposited in situ and reduced on the GO surface, resulting in the formation of the Ag-GO/CF composite. Various physicochemical characterizations were conducted to examine the interfacial interactions between CF, GO, and Ag nanoparticles. The catalytic activity of the nanocomposite was assessed by hydrogenating 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride (NaBH4). The results showed that the 10%Ag-5%GO/CF with a surface of 6 cm2 (3 × 2 cm) exhibited the highest catalytic activity, achieving a reduction efficiency of over 96% in 5 min. The 4-NP reduction reaction rate was well-fitted with a pseudo-first-order kinetics model with an apparent reaction rate constant (Kapp) of 0.676min-1. Furthermore, the Ag-GO/CF composite demonstrated remarkable stability over successive cycles, with no noticeable decrease in its catalytic activity, suggesting its promising application for long-term chemical catalytic processes. This synthesized composite can be easily added to and removed from the reaction solution while maintaining high catalytic performance in the reduction of 4-NP, and it could be beneficial in avoiding problems related to powder separation.

Hydrogenation of Alkenes Catalyzed by Mn(I) Alkyl Complexes Bearing NHC Phosphine Ligands

An efficient additive free hydrogenation of alkenes with molecular hydrogen is described. The pre‐catalyst is a well‐defined bench stable Mn(I) alkyl complex bearing a NHC phosphine ligand. These reactions are environmentally benign and atom economic, implementing an inexpensive, earth abundant non‐precious metal catalyst. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn‐alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(PC‐iPr)(CO)2(H)]. A range of mono‐ and disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation requires a reaction temperature of 60 oC. In all cases, a catalyst loading of 1 mol % and a hydrogen pressure of 50 bar was applied. A mechanism based on DFT calculations is presented which is supported by experimental studies.

Multiplicative rGO/Cu-BDC MOF for 4-nitrophenol reduction and supercapacitor applications

Two-dimensional nanosheets, with their distinct characteristics, are widely used in various applications such as water splitting, supercapacitors, catalysis etc. In this research, we produced Cu-BDC MOF nanosheets by using Cu2O nanotubes for metal ions and H2BDC as the organic linker. We combined these Cu-BDC MOF nanosheets with reduced graphene oxide (rGO) to form a nanocomposite. The collaboration between Cu-BDC MOF and rGO boosts both the catalytic reduction of 4-nitrophenol and the electrochemical capabilities. The conversion of 4-nitrophenol to 4-aminophenol is achieved using sodium borohydride as both a reducing agent and a catalyst. The study explores the impact of different concentrations of 4-nitrophenol and sodium borohydride on catalytic efficiency. The increase in sodium borohydride concentration enhances catalytic efficiency by providing more BH4− ions and electrons for the reduction process. The catalytic reduction process adheres to the Langmuir–Hinshelwood mechanism with apparent pseudo-first-order kinetics. Specifically, Cu-BDC MOF and rGO/Cu-BDC MOF exhibit specific capacities of 468.4 mA h/g and 656.4 mA h/g at a current density of 2 A/g, respectively, while also enhancing the operating voltage window. Therefore, electrodes based on rGO/Cu-BDC MOF nanosheets present a novel approach for environmental remediation and energy storage applications across various fields.

Effect of high solids loading on gas–liquid mass transfer in an oscillatory flow reactor for process intensification

A wide range of chemical processes involves three phases, where common systems have inefficient mixing and mass transfer is limited. This study uses the oscillatory flow reactor with smooth periodic constrictions (OFR-SPC) according to the patent EP3057694 (B1) to evaluate its potential on O2 mass transfer at high solids loading (10–50 % (v/v)). For that, the effect of solids (EPS, PVC) properties (concentration, density, and size) on the performance of the volumetric liquid-side mass transfer coefficient (kLa), gas holdup (εG) and Sauter mean bubble diameter (d32) using several operational conditions (oscillation amplitude and frequency, superficial gas velocity) was assessed. Results show that oscillatory conditions can influence the solids effect on kLa. At solid load (≥ 30 % (v/v)) under low oscillations, kLa decreased, εG and d32 increased, slug flow regime emerged and the OFR-SPC behaved as fixed bed reactor. Contrary, no significant influence of solid properties on kLa, and εG was observed at higher oscillations, where the reactor behaved as fluidized bed in a homogeneous flow regime. Notably, solids’ concentration (<30 % (v/v)), size and density revealed a negligible influence on mass transfer for all range of oscillations, contrary to the widespread consensus where kLa tends to decrease in conventional reactors at lower solid’s load (<15 % (v/v)), making the OFR-SPC a valuable resource for catalytic processes. The OFR-SPC demonstrated higher mass transfer rates (∼3 − fold) than conventional multiphase devices with reasonable power consumption (∼100 W/m−3(−|-)). These are remarkable results, which indicate the OFR-SPC for three-phase industrial processes intensification.

Ultrafast carrier dynamics triggered by Ga-S bond in GaZnON/CdS heterojunction for efficient photocatalytic hydrogen evolution

Constructing heterojunction has been regarded as a valid strategy of photocatalysts to promote the catalytic process. However, beyond the possible synergistic advantage from the component catalysts, the understanding of the interface effect on the photocatalytic process within heterojunction remains challenging. Herein, we prepare a novel GaZnON/CdS heterojunction photocatalyst via a robust electrostatic assembly method. The sulfur atoms in CdS are found to occupy the nitrogen vacancy over the GaZnON surface to form interfacial Ga-S bonds, which is proved as electron-transfer channel between CdS and GaZnON to realize efficient photo-induced carrier separation. The dynamic study quantificationally reveals interfacial electron transfer with a fast transfer rate of 143.8 ns−1. Thereby, the optimal composite photocatalyst reached an impressive hydrogen evolution rate of 14.76 mmol g-1h−1, as well as an impressive AQY of 36.1 % (450 nm). This work expounds the ultrafast carrier dynamics underlying interface bonds within heterojunction for weakened photo-induced carrier recombination.

(Invited) Probing Electrochemical Interfaces in Catalytic and Energy Materials and Process Using Operando Soft X-Ray Spectroscopy

Advanced energy technology arises from the understanding in fundamental science, thus rest in large on in-situ/operando characterization tools for observing the physical and chemical interfacial processes. Synchrotron based X-ray spectroscopic techniques offers unique characterization in many important energy materials of energy conversion, energy storage and catalysis in regards to the functionality, complexity of material architecture, chemistry and interactions among constituents within. However, it is challenging to reveal the real mechanism of the chemical processes.In the operando soft X-ray spectroscopy characterization of interfacial phenomena in energy materials and devices, it has been found that the microstructure and composition of materials as well as the microstructure evolution process have a great influence on performances in a variety of fields, e.g., energy conversion and energy storage materials, chemical and catalytic processes. This presentation will show how to best use the in-situ/operando soft X-ray spectroscopy characterization techniques, including soft x-ray absorption spectroscopy (XAS) and resonant inelastic soft X-ray scattering (RIXS) to investigate the real electrochemical mechanism during the operation. The experimental results show how in-situ/operando soft X-ray spectra characterization techniques uncover the phase conversion, chemical and environmental change of elements and other very important information of solid/gas and solid/liquid interfaces in real time, thus further enhance the understanding of real reaction mechanism.

Unlocking the potential of carbon quantum dots: Versatile photocatalysts for methylene blue degradation—A comprehensive review of synthesis, catalytic mechanisms, and environmental applications

AbstractCarbon Quantum Dots (CQDs) are nanoscale carbon‐based particles with unique quantum properties. Because of their customizable size, optical properties, and surface functions, CQDs are frequently used in a wide range of applications. The present thorough analysis delves into the crucial function of CQDs in the photocatalytic breakdown of Methylene Blue (MB), providing valuable perspectives on their production, attributes, and catalytic processes. The effects of pH, wavelength, intensity, and other variables on the effectiveness of MB degradation are covered in detail. An analytical review of the kinetic models used to estimate the deterioration process is given. For improved stability and recyclability, the synergistic effects of CQD‐based composites and developments in catalyst immobilization techniques are examined. Prospects for the future center on reactor designs, integration into large‐scale water treatment systems, and optimization of CQD features. The research highlights the revolutionary potential of CQDs in transforming wastewater treatment and advancing environmentally sound solutions.

Interface Engineering of Transition Metal-Based Heterostructure Electrocatalysts for Enhanced Hydrogen Evolution Reaction

Electrochemical water splitting to produce clean hydrogen plays a significant role in the development of the hydrogen economy. The rational design of highly efficient and inexpensive electrocatalysts is critical for improving water electrolysis efficiency. Herein, we report the fabrication of heterostructure monometallic, bimetallic, and trimetallic sulfides on Ni foam (NF) as porous self-supported electrodes for hydrogen evolution reaction (HER) via an energy-saving electrodeposition process. Molybdenum-cobalt-nickel sulfide electrode (MoCoNiS@NF) only requires a low overpotential of 114 mV to produce a current density of 10 mA cm-2 for HER, compared with nickel sulfides (NiS@NF, 142 mV) and cobalt-nickel sulfides (CoNiS@NF, 129 mV). The desirable HER performance of MoCoNiS@NF results from the synergistic effect of heterostructure interfaces of multi-metal sulfides, providing high intrinsic catalytic activity and a large amount of catalytic active sites. Electrochemical impedance spectroscopy and Tafel slope analysis proved the fast reaction kinetics of MoCoNiS@NF toward HER. Our present work provides valuable insights into the working mechanisms behind the HER catalytic process and new perspectives for the future design of cost-effective electrocatalysts for HER.

(Invited) Nanoarray Configured Monoliths for Self-Monitored Multi-Phase Reactive Processes

The incorporation of multiple functions synergistically into one device or platform can enable additions of application merits such as light weight, ease for system integration, reduced system complexity, cost-effectiveness, and programmability. This is especially true for usually complex energy, environmental, and biological systems with the integration need of many active or passive devices and components of various functionalities. In this work, we demonstrated a compact nanoarray configured monolith design with the ability to function as both a catalyst and a sensor to enable the self-monitoring of the complex multi-phase catalytic reaction processes during operation. A bimodular approach has been realized using both electrical and electrochemical interrogation modes for reactive gas and solid phase monitoring directly using the built-in catalysts. This new type of compact and built-in monolithic sensor configuration can lower the catalytic energetics and detect gas/solid composition semi-quantitatively at room temperature up to elevated temperature. Robust calibration curves of built-in sensor responses can be achieved with facile data processing and analyzing. The built-in monolith sensor shows good sensitivity and good selectivity sufficient for the self-monitoring of the reaction process. Besides, the nanoarray based monolith device has shown good environmental tolerance toward practical applications. Such compact monolithic device can serve as a self-monitored reactor, filter, and other function component that can potentially allow in-situ and real time monitoring and functional process control in complex and reactive physical and chemical environments. With further refining of the design and functional integration, this new type of smart monolithic device can provide necessary data and knowledge for future computation-driven situational awareness prediction and intelligent control of various complex dynamic processes and systems.

Development of a Rotating Disk Electrode-Based Ru-Leaching AST for PEM Fuel Cell Reformate Anode Ru-Pt/C Catalysts

Extreme heavy-duty (e.g., maritime) applications of PEM fuel cells often require liquid hydrogen carriers as fuel.[1] In the case of methanol, it is mixed with steam and converted to hydrogen and CO2 in a catalytic reformation process.[2] While a multi-step approach, including the water-gas shift reaction and selective oxidation processes, is typically undertaken to fully convert methanol to hydrogen and CO2, low ppm-level amounts of CO remain in the resulting “reformate hydrogen” gas stream.[3] This CO concentration is significantly higher than deemed non-poisonous to the platinum catalyst on the anode (i.e., < 0.2 ppm),[4] and a more CO-tolerant anode catalyst is required. To address this issue, RuPt-alloy nanoparticles supported on carbon are employed, leading to CO-tolerance of the HOR-catalysts on the anode at reformate conditions.[3] However, previous works found that during operation, Ruthenium leaches from the anode catalyst layer and travels through the membrane, subsequently depositing on the platinum nanoparticles, effectively poisoning the cathode Pt/C catalyst and significantly reducing its activity towards the oxygen reduction reaction.[3,5] To eliminate or reduce Ru-leaching from RuPt/C catalysts while retaining its inherent CO-tolerance, efforts tuning the catalyst’s (surface) composition were made. However, as the leaching of Ru in fuel cells occurs over thousands of hours, the use of an accelerated stress test (AST) for reformate anodes is required. In one of our previous efforts, an AST for Ru-leaching in fuel cells was used to study RuPt/C degradation.[3] However, the amount of material, MEA preparation time and AST measurement time required for such a test was found to be too high for catalyst development. Additionally, fuel cell measurement capacity is limited due to its high cost and the quantification of the total amount of Ru-leached remained challenging.In light of this, in this work, we developed an AST aimed at achieving a reliable yet short and less material consuming protocol, enabling us to quantitatively investigate the Ru-leaching of RuPt-materials during catalyst development. This was achieved by using the rotating disk electrode (RDE) configuration, a well-established electrocatalyst characterization and pre-testing method.[6] The RDE-based AST-protocol was developed using three commercial RuPt-catalysts with varying Ru:Pt ratios of 1:1, 1.5:1, and 2:1 while possessing a comparable particle size and electrochemical surface area. Additionally, the commercial catalyst with a 2:1 atomic ratio catalyst was used in a heat-treated form leading to a larger particle size and lower ECSA.The AST-protocol was comprised of a series of voltammetric cycles aimed at aging the catalyst. During the protocol development, the number of aging cycles (100 – 1000), the scan rate (10 – 100 mV s-1), and the upper inversion potential (0.8 – 0.9 VRHE) of the cyclic voltammograms were varied to investigate their influence on catalyst degradation. This was achieved by collecting the electrolyte (Ar-saturated 0.1M H2SO4) after the AST-cycles and subsequent quantification of the dissolved Ru using inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, the change in the surface composition was qualitatively analyzed by comparing the CO-oxidation peak shape and position before and after the AST-cycling. Examples of the ICP-OES and CO-stripping results for the systematic investigation of the influence of cycle number and scan rate on the 1.5:1 Ru:Pt catalyst using an upper inversion potential of 0.85 VRHE are displayed in Figure 1. Based on this rigorous investigation of the parameters influencing Ru-dissolution in an RDE-environment and after the necessary validation of the results found using the finalized protocol in MEA-based testing,[5] the developed protocol could subsequently be applied to self-synthesized RuPt/C materials as well as RucorePtshell-catalysts.In summary, this contribution showcases the development of a reliable rotating disk electrode-based accelerated stress test protocol for Ru-leaching from RuPt/C catalysts. Furthermore, its validation with commercial catalysts as well as its application to self-synthesized PEM fuel cell anode catalysts for use with reformate hydrogen, is presented.

(Invited) Thermal and Plasmon-Mediated Catalytic Transfer Hydrogenation Reactions on Nanostructured Metal Surfaces

Catalytic hydrogenation reactions play crucial roles in fine chemical production and pharmaceutical synthesis. Compared to direct hydrogenation of organic compounds with pressurized hydrogen gas, catalytic transfer hydrogenation reactions using inexpensive and readily accessible small molecules as hydrogen-donors has been considered as a more versatile, scalable, and sustainable pathway toward enhanced chemoselectivity under mild reaction conditions. Noble metal nanoparticles, especially those within the sub-5 nm size regime, can efficiently catalyze the dehydrogenation of a series of hydrogen-storing molecules, such as ammonia borane, hydrazine, formaldehyde, formic acid, and isopropanol, to produce surface-adsorbed hydrogen species that actively hydrogenate a variety of organic substrate molecules. The transfer hydrogenation/hydrogenolysis reactions are mechanistically complex, and may occur selectively along multiple distinct pathways, exhibiting kinetic features signifying the Langmuir–Hinshelwood, Eley–Rideal, autocatalysis, and reversible reaction mechanisms, respectively, depending on the compositions of the metal catalysts and the chemical nature of the hydrogen donors. In this talk, I will share with the audience some new insights concerning the detailed mechanisms of transfer hydrogenation reactions over metal nanocatalyst surfaces. We employ surface-enhanced Raman scattering (SERS) as an in situ fingerprinting spectroscopic tool to precisely resolve the detailed structural evolution of molecular adsorbates during catalytic reactions, based upon which the key intermediates along different reaction pathways are unambiguously identified. The results of deliberately designed in situ SERS measurements show that the chemoselective transfer hydrogenation of nitrophenyl isocyanide by ammonia borane may proceed on noble metal nanocatalyst surfaces selectively through either a unimolecular or a bimolecular pathway, depending on how the nitrophenyl isocyanide adsorbates interact with the metal nanoparticle surfaces. The experimental observations are corroborated by density functional theory calculations, which shed light on the underlying relationships between catalyst-adsorbate interactions and reaction pathway selection. We have further demonstrated that the photoexcited plasmonic hot carriers in the metal nanoparticles can be effectively harnessed to fine-regulate the activation energy barriers associated with the rate-limiting steps for the transfer hydrogenation of nitrophenyl isocyanide on Pd nanocatalyst surfaces when ammonium formate serves as the hydrogen donor. Our results clearly demonstrate the feasibility of using plasmonic hot carriers to kinetically modulate catalytic molecule-transforming processes.

Novel Lewis Acid-Base Interactions in Polymer-Derived Sodium-Doped Amorphous Si-B-N Ceramic: Towards Main-Group-Mediated Hydrogen Activation.

Interest is growing in transition metal-free compounds for small molecule activation and catalysis. We discuss the opportunities arising from synthesizing sodium-doped amorphous silicon-boron-nitride (Na-doped a-SiBN). Na+ cations and 3-fold coordinated BIII moieties were incorporated into an amorphous silicon nitride network via chemical modification of a polysilazane followed by pyrolysis in ammonia (NH3) at 1000 °C. Emphasis is placed on the mechanisms of hydrogen (H2) activation within Na-doped a-SiBN structure. This material design approach allows the homogeneous distribution of Na+ and BIII moieties surrounded by SiN4 units contributing to the transformation of the BIII moieties into 4-fold coordinated geometry upon encountering H2, potentially serving as frustrated Lewis acid (FLA) sites. Exposure to H2 induced formation of frustrated Lewis base (FLB) N-= sites with Na+ as a charge-compensating cation, resulting in the in situ formation of a frustrated Lewis pair (FLP) motif (≡BFLA⋅⋅⋅Hδ-⋅⋅⋅Hδ+⋅⋅⋅:N-(Na+)=). Reversible H2 adsorption-desorption behavior with high activation energy for H2 desorption (124 kJ mol-1) suggested the H2 chemisorption on Na-doped a-SiBN. These findings highlight a future landscape full of possibilities within our reach, where we anticipate main-group-mediated small molecule activation will have an important impact on the design of more efficient catalytic processes and the discovery of new catalytic transformations.

Changing Mechanisms for CO2 Reduction to Formate Via Protonation of the Catalyst

Electrochemical reduction reaction of CO2 (CO2RR) is a promising method to transform CO2 to useful products for consumption such as formic acid, carbon monoxide, or methane. Simply increasing the driving force of a catalytic process to speed up the rate of CO2 reduction is unviable because of the competing Hydrogen Evolution Reaction (HER) pathway and of increased energy cost. Controlling the reactivity of active intermediates is of substantial importance for such processes. [Fe4N(CO)12]− is a formate selective electrocatalyst previously studied by our group and was modified through protonation and replacement of several CO ligands with triethylphosphines (PEt3) to synthesize [HFe4N(PEt3)4(CO)8] . This PEt3 substituted, pre-protonated analog of [Fe4N(CO)12]− exhibits altered rates compared to a non-protonated analog which we attribute to a switch in mechanism. We further explore explanations for different rates despite similar “active intermediates” and similar driving force using Cyclic Voltammetry (CV).

(Invited) Design of Photoactive Inorganic Nanomaterials for Environmental Challenges

Nowadays, one of the main technological challenges that we are facing is the ability to provide a sustainable supply of clean energy and, among all renewable sources, solar energy displays the greatest potential. Recently, the development of novel synthetic strategies has led to the preparation of nanostructured materials displaying unique properties compared to the bulk counterpart systems, with controlled and tunable morphologies able to enhance the activity and selectivity of a catalytic process. In particular, nanostructured materials synthesized via the bottom–up approach present an opportunity for future generation manufacturing of devices.This talk will focus on the importance of tuning the morphological features of a catalyst as a strategy to improve its optical and photocatalytic properties, focusing on how rationally designing inorganic materials at the nanoscale can lead to morphologies and structures suitable to enhance the performance of industrially and environmentally important processes. The talk will discuss some environmental applications that can be addressed by photoactive multi-component oxide systems synthesized via the bottom–up approach, highlighting their structure-reactivity relationship. Water contamination, in particular, is one of the upfront issues to be solved and complex organic molecules and pharmaceuticals, including antibiotics, are gaining attention due to their abuse and their low degradability. Photocatalytic drugs degradation will be presented as a successful case history [1-3] to provide inspiration to produce cheap, environmentally friendly, stable, and efficient photocatalysts, which hold a great potential for the development of new technologies not only for water remediation applications but also for energy applications in the field of solar fuel production.[1] E. Moretti, L. Storaro, A. Talon, P. Riello, A. Infantes Molina, E. Rodríguez-Castellón, Appl. Catal. B: Environmental 168 (2015) 385.[2] M. Telkhozhayeva, B. Hirsch, R. Konar, E. Teblum, R. Lavi, M. Weitman, B. Malik, E. Moretti, G.D. Nessim, Appl. Catal. B: Environmental 318 (2022) 121872.[3] L. Liccardo, M. Bordin, P.M. Sheverdyaeva, M. Belli, P. Moras, A. Vomiero, E. Moretti, Adv. Funct. Mater. 33 (2023) 2212486.

Water Splitting and Beyond

Hydrogen (H2) is a clean and environmentally friendly fuel, showcasing significant potential as a viable substitute for traditional fossil energy sources. Electrolysis, particularly the electrolytic splitting of water, emerges as one of the most environmentally benign methods for producing H2.1 Recent advancements have witnessed the emergence of cost-effective and durable catalysts, predominantly leveraging transition metals, demonstrating remarkable efficiency for water splitting Our ongoing research endeavors aim to push the boundaries further by exploring unconventional (non-oxide) catalysts based on non-noble metals. The objective is to identify catalysts that exhibit superior overall catalytic efficiency by a comprehensive investigation into the structural transformations, active sites, surface, and bulk structures under dynamic conditions. Additionally, we are delving into the influence of precatalysts on the properties of the final catalyst, striving for a holistic understanding to optimize the catalytic process. Water splitting is hindered by the anodic oxygen evolution reaction (OER), a process entailing four-electron transfer and numerous high-energy reaction intermediates.2 Partly, electrochemical organic oxidation reactions (OOR) can effectively supersede the sluggish OER (hybrid-water electrolysis), and accelerate the overall hydrogen production rate.3 This also significantly enhances the techno-economic viability of water-splitting as selective high-valued organic oxidation products are formed at the anode, as opposed to the less valuable oxygen.4 This talk will shed light on the recent developments of selected catalysts for electrocatalytic OER and OOR and will discuss the dynamic state of the catalysts via comprehensive in-situ and ex-situ techniques.5 The ultimate goal is to pave the way toward a concept-guided design system that extends beyond conventional water electrolysis.

(Invited) 3D Printing of 2D Materials for Optimized Electrochemical Performance

Electrochemical energy storage (EES) and conversion devices (e.g. batteries, supercapacitors, and reactors) are emerging as primary methods for global efforts to shift energy dependence from limited fossil fuels towards sustainable and renewable resources. These devices, while showing great potential for meeting some key metrics set by conventional technologies, still face significant limitations. For example, an EES device tends to exhibit large energy density (e.g. lithium-ion battery) or power density (e.g. supercapacitor), but not both. This inability of a single device to simultaneously achieve both metrics represents a major obstacle to widespread adoption of EES devices. Similarly, many catalytic processes depend on expensive platinum group metals (PGM) because non-PGM materials have poor performance or durability. Though the integration of 2D materials (e.g. graphene, dichalcogenides, MXene, etc.) into electrochemical devices has yielded some exciting results towards tackling these issues, significant improvements are still needed. One approach to optimizing the performance of these devices is to focus on one of the fundamental processes that occur in these systems: mass (or charge) transport. The efficient transport of ions within EES and conversion devices is critical to realizing better performance and durability. The pore structure of the electrode is a key factor in determining this transport phenomena, but in many cases, engineering the pore structure in a highly deterministic fashion can be challenging. In this work, we explore a number of additive manufacturing methods (e.g. direct ink write, projection microstereolithography, etc.) to engineer the pore structure of device electrodes. We also determine effective electrode geometries using both simple theory and topology optimization techniques. The topology optimization couples the solution of the forward electrochemical problem over the full electrode domain with gradient-based optimization. The output of our code is a three-dimensional CAD representation which optimizes over specific performance metrics and which can be used to print functional electrodes. This work provides a systematic path toward automated design and fabrication of engineered electrodes with precise control over the fluid and species distribution.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Built-in electric field control of electron redistribution (NiFe-based electrocatalyst) with efficient overall water splitting at industrial temperature

Nickel-iron layered double hydroxide (NiFe-LDH) is hindered in its further development in water splitting due to its slow kinetics of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this study, the synthesis of OER (FeO(OH)/NiFe-LDH) and HER (Fe7S8(NiS)/NiFe-LDH) catalysts endowed with inherent electric fields exhibited exceptional electrocatalytic properties. The presence of the built-in electric field modulated the redistribution of electrons within the catalyst, while the formation of a heterostructure preserved the intrinsic characteristics of the catalyst. Moreover, this electron redistribution optimized the catalyst’s adsorption of reaction intermediates (O*, OH*, OOH*, and H*) during the catalytic process, thereby enhancing the performance of both OER and HER. The electrolytic cell, equipped with these catalysts, achieved the current density of 10 mA cm−2 at a remarkably low potential of 1.409 V under industrial temperature conditions and demonstrated an ultra-long-term stability of 200 h.

Interface engineering of the dz2 electrons mobility for single atom catalytic activity and selectivity

Transition metal singlet embedded in nitrogen-doped carbon material (M-N-C) has been demonstrated as a promising electrochemical oxygen reduction reaction (ORR) catalyst; however, the unsatisfying activity and production selectivity have hampered its widespread applications in energy storage and conversion technologies. Herein, interface engineering by facilitating M-N-C catalysts (M from 3d to 4d electron-containing elements) with MXene has been utilized to regulate their ORR performance. It is found that the charge transfer occurring within the interface not only tunes the electron occupancy of the 3d/4d orbitals of the metal site, but also delocalizes the population of the dz2 states. This alternation enhances the mobility of the electrons and promotes the 4e catalytic process thermodynamically. Meanwhile, the formation of ∗HOOH, the key reaction intermediate for 2e reaction, is hindered due to the alleviation of the binding capacity, which is beneficial to improve production selectivity. This study provides foundational understanding for the ORR catalytic mechanism at the atomic level and opens up new avenues for designing high-demanded electrocatalysts.

Advancing Organic Photoredox Catalysis: Mechanistic Insight through Time-Resolved Spectroscopy.

The rapid development of light-activated organic photoredox catalysts has led to the proliferation of powerful synthetic chemical strategies with industrial and pharmaceutical applications. Despite the advancement in synthetic approaches, a detailed understanding of the mechanisms governing these reactions has lagged. Time-resolved optical spectroscopy provides a method to track organic photoredox catalysis processes and reveal the energy pathways that drive reaction mechanisms. These measurements are sensitive to key processes in organic photoredox catalysis such as charge or energy transfer, lifetimes of singlet or triplet states, and solvation dynamics. The sensitivity and specificity of ultrafast spectroscopic measurements can provide a new perspective on the mechanisms of these reactions, including electron-transfer events, the role of solvent, and the short lifetimes of radical intermediates.

Catalytic Approaches to Tackle Mixed Plastic Waste Challenges: A Review.

Plastics are widely used materials in our daily lives and various industries due to their affordability and versatility. The massive production of plastic waste, however, has recently emerged as a pressing environmental concern across all media. To address this, emerging technologies are being explored for the sustainable valorization of postconsumer plastic wastes including thermochemical, physical, and catalytic processes aimed at transforming them into higher value-added products. However, the chemical recycling of mixed plastic wastes poses a formidable challenge due to the diverse array of monomers and catalyst systems involved, each employing distinct mechanisms. Complicating matters further is that contaminants reduce catalytic efficacy, requiring rigorous and labor-intensive separation and purification processes to extract individual plastic streams from practical plastic waste mixtures. Consequently, the majority of such mixtures often end up in incineration and landfills, perpetuating environmental and societal challenges, such as leachate, carbon dioxide emissions, and other air pollutants. This review will introduce current technical developments available for recycling practical plastic waste mixtures through catalytic processes. The current challenges in process performance, low selectivity of the desired products, and catalyst deactivation from the catalysis of plastic waste mixtures are also discussed. Promising approaches to overcome the problems are suggested in future research directions.