Alloying as a Strategy to Boost the Stability of Copper Nanocatalysts during the Electrochemical CO2 Reduction Reaction

Interfacial Metal Oxides Stabilize Cu Oxidation States for Electrocatalytical CO2 Reduction

Modulating the oxidation state of copper (Cu) is crucial for enhancing the electrocatalytic CO2 reduction reaction (CO2RR), particularly for facilitating deep reductions to produce methane (CH4) or multi-carbon (C2+) products. However, Cuδ+ sites are thermodynamically unstable, fluctuating their oxidation states under reaction conditions, which complicates their functionality. Incorporating interfacial metal oxides has emerged as an effective strategy for stabilizing these oxidation states. This review provides an in-depth examination of the reaction mechanisms occurring at oxide-modified Cuδ+ sites, offering a comprehensive understanding of their behavior. We explore how Cu/metal oxide interfaces stabilize Cu oxidation states, showing that oxides-modified Cu catalysts often enhance selectivity for C2+ or CH4 products by stabilizing Cu+ or Cu2+ sites. In addition, we discuss innovative strategies for the rational design of efficient Cu catalytic sites tailored for specific deep CO2RR products. The review concludes with an outlook on current challenges and future directions, offering new insights into the rational design of selective and efficient CO2RR catalysts.

Structural Reconstruction of Copper-Based Catalysts in CO2 Electroreduction Reaction: A Comprehensive Review

The escalating concerns over climate change and environmental pollution have intensified the pursuit for sustainable solutions to mitigate CO2 emissions, with the electrochemical CO2 reduction reaction (CO2RR) emerging as a promising strategy to convert CO2 into valuable chemicals and fuels. Central to this process is the development of efficient electrocatalysts, where Cu-based catalysts have garnered significant attention due to their high activity towards multi-carbon products. However, understanding of structural reconstruction of Cu-based catalysts under operational conditions presents a substantial challenge, complicating the identification of real active sites and the elucidation of structure-performance relationships. Herein, we first highlight the fundamental principles governing the structural reconstruction in CO2RR, encompassing both thermodynamic and kinetic perspectives. We then introduce advanced Operando techniques employed to monitor the structural changes of catalysts. The review further delves into the dynamic evolution behaviors of Cu-based catalysts, including atomic rearrangement and morphology evolution, with a focus on correlating these behaviors with catalytic properties such as activity, selectivity, and stability. Finally, we discuss cases of emerging strategies, such as heteroatom doping and electrolyte engineering, that hold promise for manipulating the structural reconstruction of Cu-based catalysts, and we explore future opportunities in this rapidly evolving field.

Electronic Modulation of Bismuth by g-C3N4 Constructs Electron-Enriched Active Sites for Accelerated CO2 Electroreduction to Formate

Electrochemical reduction of CO2 (ECO2RR) to formate represents a promising approach to achieving carbon neutrality, yet it faces significant challenges due to the low adsorption efficiency of the CO2 intermediates. In this study, we developed a highly dispersed electron-rich Bi metal catalyst, utilizing low-cost g-C3N4 as a nonmetallic support and electron donor. This design created a conductive network and a multielectron environment around the Bi atoms that facilitated dynamic interfacial charge transfer from g-C3N4 to Bi, thus enhancing the catalytic efficiency of active sites. The assembly catalyst exhibited a formate selectivity of over 90% within a wide potential window and maintained stable catalytic activity in simulated seawater solutions. In situ Raman spectroscopy and DFT calculations indicated that the incorporation of the nonmetallic support shifted the Bi-p band center to more negative values while increasing Bader charge transfer between Bi and *OCHO intermediates. This indicated enhanced adsorption of the *OCHO intermediate by electron-rich Bi, thus improving the selectivity and activity for formate production.

Earth-abundant Ni-Zn nanocrystals for efficient alkyne semihydrogenation catalysis

The development of catalysts that are based on earth-abundant metals remains a grand challenge. Alloy nanocrystals (NCs) form an emerging class of heterogeneous catalysts, offering the promise of small, uniform catalysts with composition-control. Here, we report the synthesis of small Ni and bimetallic Ni-X (X= Zn, Ga, In) NCs for alkyne semihydrogenation catalysis. We show that Ni3Zn NCs are particularly reactive and selective under mild reaction conditions and at low loadings. While bimetallic NCs are all more selective than pure Ni NCs, Ni-Zn NCs also maintain excellent reactivity compared to Ni-Ga and Ni-In alloys. Ab-initio calculations can explain the differences in reactivity, indicating that, unlike Ga and In, Zn atoms interact with the substrates. We further show that Ni3Zn NCs are robust and tolerate a broad range of substrates, which may be linked to the favorable amine-terminated surface.

Controlled synthesis of metal-based Janus nanostructures for tandem electrocatalytic carbon dioxide reduction

Electrochemical carbon dioxide reduction reaction (CO2RR) possesses huge potential for achieving carbon neutrality by reducing greenhouse-gas CO2 to value-added chemicals/fuels with sustainable energy. However, obtaining highly selective and long-term stable catalysts for CO2RR is still challenging. Recently, metal-based Janus nanostructures (JNSs) have demonstrated unique advantages in addressing this issue in CO2RR via tandem catalysis. Herein, we systematically summarize the recently developed metal-based JNSs for electrocatalytic CO2RR. The synthesis methods are first introduced, including three representative methods (seed-mediated growth, dimerization, and selective-etching) and the strategy for constructing specific facets or unconventional phases in metal-based JNSs. Then, the application of metal-based JNSs in CO2RR toward the generation of single-carbon and multi-carbon products is elaborated, along with the corresponding catalytic mechanisms. The structural reconstruction of metal-based JNSs is also discussed in detail. Finally, we briefly summarize the recent advances and provide personal perspectives in this research direction.

Nitrate Electroreduction to Ammonia Over Copper-based Catalysts

The electrocatalytic reduction of nitrate (NO3 -) to ammonia (NH3) holds substantial promise, as it transforms NO3 - from polluted water into valuable NH3. However, the reaction is limited by sluggish kinetics and low NH3 selectivity. Cu-based catalysts with unique electronic structures demonstrate rapid NO3 - to NO2 - rate-determining step (RDS) and fast electrocatalytic nitrate reduction reaction (eNO3RR) kinetics among non-noble metal catalysts. Nonetheless, achieving high robustness and selectivity for NH3 with Cu-based catalysts remains a significant challenge. This review provides a comprehensive overview of the reaction mechanisms in eNO3RR, highlights how the structures of monometallic and bimetallic Cu-based catalyst affect catalytic properties, and discusses the current challenges as well as prospects in eNO3RR.

Rational Construction of Cu Active Sites for CO2 Electrolysis to C2+ Product

Electrocatalytic CO2 reduction reaction (CO2RR) has emerged as a promising approach in advancing towards carbon neutrality and addressing renewable energy intermittency. Copper-based catalysts have received much attention due to their high catalytic activity to convert CO2 into high value-added C2+ products. However, CO2RR exhibits a diversity of reduction products and unavoidable hydrogen precipitation side reactions due to the moderate adsorption strength of *CO on the copper surface and the fact that the electrode potential for CO2 reduction is very close to that for hydrogen precipitation reduction. Here, we summarize recent advances in the structural design and active site construction of copper-based catalysts for CO2RR, and investigate their effects on the improvement of CO2RR performance, with the aim of deepening the understanding of catalyst structure and active sites, thereby facilitating the design of more efficient copper-based catalysts for the sustainable production of value-added chemicals.

In Situ High Selectivity Contact-Electroreduction of CO2 to Methanol Using an Imine-Mediated Metal-Free Vitrimer Catalyst

Metal catalysts for the CO2 reduction reaction (CO2RR) face challenges such as high cost, limited durability, and environmental impact. Although various structurally diverse and functional metal-free catalysts have been developed, they often suffer from slow kinetics, low selectivity, and nonrecyclability, significantly limiting their practical applications. In this study, we introduce a recyclable nonmetallic polymer material (vitrimer) as a catalyst for a new platform in contact-electrocatalysis. This approach harnesses the contact charges generated between water droplets and vitrimer to drive CO2RR, achieving methanol selectivity exceeding 90%. The imine groups within the vitrimer play a dual role, facilitating CO2 adsorption and enriching friction-generated electrons, thereby mediating efficient electron transfer between the imine groups and CO2 to promote CO2RR. After 84 h of CO2RR, the system achieved a methanol production rate of 13 nmol·h-1, demonstrating the excellent stability of the method. Moreover, the vitrimer retains its high-performance electrocatalytic activity even after recycling. Mechanistic studies reveal that, compared to traditional metal catalysts, the N─O bond in the imine, which adsorbs the key intermediate *OCH3, breaks more readily to produce methanol, resulting in enhanced product selectivity and yield. This efficient and environmentally friendly contact-electroreduction strategy for CO2 offers a promising pathway toward a circular carbon economy by leveraging natural water droplet-based contact-electrochemistry.

Highly Selective Electroreduction of CO2 to CH4 on Cu-Pd Alloy Catalyst: the Role of Palladium-Adsorbed Hydrogen Species and Blocking Effect

Electroreduction of CO2 to chemical fuels offers a promising strategy for controlling the global carbon balance and addressing the need for the storage of intermittent renewable energy. In this work, it is demonstrated that tuning adjacent active sites enables the selection of different reaction pathways for generating C1 or C2 products during the electroreduction of CO2. Cu and Cu-Pd alloy catalysts with different atomic ratios are synthesized and investigated to elucidate their different electroreduction selectivities for CO2 electroreduction. Cu catalyst favors the formation of C2 products since the neighboring active Cu sites are beneficial for coupling adjacently adsorbed *CO and *CHO intermediates. Cu alloyed with Pd introduces a blocking effect and increases the intermolecular distance between adjacent adsorbed *CO and *CHO intermediates. Therefore the selectivity for the C2H4 pathway decreas while the CH4 pathway is enhanced. Moreover, the existence of adsorbed *H species on Pd atoms also played a significant role in boosting CO2 electroreduction to CH4 by facilitating the hydrogenation of *CO intermediates. This work reveals the key role of *H species adsorbed on Pd atoms and the blocking effect between active sites for CH4 formation, which is helpful for the design of copper-based catalysts for desired products.

Non-Aqueous Electrochemical CO2 Reduction to Multivariate C2-Products Over Single Atom Catalyst at Current Density up to 100 mA cm-2

Electrochemical CO2 reduction reaction (CO2-RR) in non-aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO2 solubility and limits the formation of HCO3 - and CO3 2- anions. Metal-organic frameworks (MOFs) in non-aqueous CO2-RR makes an attractive system for CO2 capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)-based porphyrin MOF, specifically PCN-222, metalated with a single-atom Cu has been explored, which serves as an efficient single-atom catalyst (SAC) for CO2-RR. PCN- 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single-atom Cu site, facilitating complete reduction of C2 species under non-aqueous electrolytic conditions. The current densities achieved (≈100 mA cm- 2) are 4-5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C2 products, which have never been achieved previously in non-aqueous systems. Characterization using X-ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO2 reduction, benchmarking PCN-222(Cu) for MOF-based SAC electrocatalysis.

N-Heterocyclic Carbene Polymer-Stabilized Au Nanowires for Selective and Stable Reduction of CO2

The structural stability of nanocatalysts during electrochemical CO2 reduction (CO2RR) is crucial for practical applications. However, highly active nanocatalysts often reconstruct under reductive conditions, requiring stabilization strategies to maintain activity. Here, we demonstrate that the N-heterocyclic carbene (NHC) polymer stabilizes Au nanowire (NW) catalysts for selective CO2 reduction to CO over a broad potential range, enabling coupling with Cu NWs for one-step tandem conversion of CO2 to C2H4. By combining the hydrophobicity of the polystyrene chain and the strong binding of NHC to Au, the polymer stabilizes Au NWs and promotes CO2RR to CO with excellent selectivity (>90%) across -0.4 V to -1.0 V (vs RHE), a significantly broader range than unmodified Au NWs (-0.5 V to -0.7 V). Stable CO2RR at negative potentials yields a high jCO of 142 A/g Au at -1.0 V. In situ ATR-IR analysis indicates that the NHC polymer regulates the water microenvironment and suppresses hydrogen evolution at high overpotential. Moreover, NHC-Au NWs maintain excellent stability during 10 h of CO2RR testing, preserving the NW morphology and catalytic performance, while unmodified NWs degrade into nanoparticles with reduced activity and selectivity. NHC-Au NWs can be coupled with Cu NWs in a flow cell to catalyze CO2RR to C2H4 with 58% efficiency and a partial current density of 70 mA/cm2 (overall C2 product efficiency of 65%). This study presents an adaptable strategy to enhance the catalyst microenvironment, ensure stability, and enable efficient tandem CO2 conversion into value-added hydrocarbons.

Atomic Layered ZnO Between Cu Nanoparticles and a PVP Polymer Layer Enable Exceptional Selectivity and Stability in Electrocatalytic CO2 Reduction to C2H4

This study employs a chemically controlled strategy to construct a few-atomic-layer ZnO structure integrated with polyvinylpyrrolidone (PVP) and nanoscale metallic copper on active carbon. Hydrogen-bond interactions from PVP's N-vinylpyrrolidone allow ZnO to retain a specific proportion of metal atoms, confining electrons at the Cu/ZnO interface to form CuZn nanoalloy clusters. The nanoalloy's dual role in promoting CO adsorption and C─C coupling synergistically boosts C2H4 production during electrochemical CO2 reduction (ECR). Rapid Cu regeneration further increases adsorbed hydrogen (Hads) from water splitting, achieving a remarkable C2H4 selectivity of ≈50.2% with stable performance over 10 h. The Zn→Cu electron confinement and interfacial synergy at the organic-oxide-metal heterojunction underscore the catalyst's superior efficiency, offering a promising pathway for sustainable CO2-to-C2H4 conversion.

Efficient Electrochemical Reduction of CO2 to C2H4 Over Low Work Function Cu/ZnO Film Catalysts

Cu-based catalysts for electrochemical CO2 reduction reactions facilitate the transformation of CO2 into economically viable multicarbon products. There remains a pressing need to design efficient, stable, and cost-effective catalysts to enhance the selectivity for these multicarbon products. Metal-oxide heterogeneous interface can modify the electronic structure of metal surfaces, influencing the adsorption energy of crucial intermediates and thereby enhancing the selectivity for multicarbon products. In this study, Cu/ZnO electrodes are prepared by magnetron sputtering to achieve a Faraday efficiency of 51.2% for C2H4 at -1.17 V. The Cu/ZnO heterogeneous interface provided abundant active sites for the reaction, and the lower work function facilitated the multi-electron transfer process necessary for the reduction of CO2 to C2H4, thereby enhances the catalytic performance. DFT calculations reveal that the upward shift in the d-band center of Cu/ZnO, compared to pure Cu, enhances the adsorption energy of the crucial intermediate *CO. Moreover, the C-C coupling achieved on Cu/ZnO through the *CHO-*CHO pathway, which features lower energy barriers, ensures high selectivity in the conversion of CO2 to C2H4. This work provides a promising and effective strategy for the large-scale development of metal-oxide catalysts for the electrochemical reduction of CO2 to C2H4.

Impact of Heterocore Atoms on CO2 Electroreduction in Atomically Precise Silver Nanoclusters

Understanding the effect of internal atoms in metal nanoparticles on heterogeneous catalytic processes is crucial for achieving high activity and selectivity. This requires meticulous synthetic control over the size, composition, and atomic arrangement of nanoparticles. Here, we report the design of ligand-exchange-induced structure transformation and nanomolecule-templated atomic-level galvanic exchange strategies to synthesize PtAg24(IPBT)18 (denoted as PtAg24) and AuAg24(IPBT)18 (denoted as AuAg24) nanoclusters (NCs). Both NCs exhibit identical total metal atom and ligand (IPBT: 2-isopropylbenzenethiolate) counts, as well as atomic-level structure, except for the difference in the core atom (Pt and Au). Using these model NCs, we uncover the impact of heterocore atoms on the electrochemical CO2 reduction reaction (eCO2RR) activity and selectivity. The central Pt atom in PtAg24 is less favorable for eCO2RR activity, with an activity approximately 4 times smaller than that of Au in AuAg24. The eCO2RR product CO selectivity is <30% for PtAg24, while it exceeds 70% for AuAg24, revealing the critical role of the central atom in surface catalytic pathways. Furthermore, AuAg24 exhibits high activity, with a CO partial current density of -202.2 mA cm-2, and stability over 24 h, retaining 90% CO selectivity in a membrane electrode assembly configuration. Operando spectroscopy and density functional theory calculations suggest the weaker adsorption of *CO intermediates and smaller energy barrier facilitate CO production on AuAg24 compared to PtAg24, providing valuable atomistic insights into the reaction intermediates and mechanism. The findings in this work will inspire the design of more atomically precise model nanocatalysts to explore the role of their remarkable features in the catalytic activity and selectivity for renewable energy conversion and storage.

Strategies for Enhancing Stability in Electrochemical CO2 Reduction

The electrochemical CO2 reduction reaction (CO2RR) holds significant promise as a sustainable approach to address global energy challenges and reduce carbon emissions. However, achieving long-term stability in terms of catalytic performance remains a critical hurdle for large-scale commercial deployment. This mini-review provides a comprehensive exploration of the key factors influencing CO2RR stability, encompassing catalyst design, electrode architecture, electrolyzer optimization, and operational conditions. We examine how catalyst degradation occurs through mechanisms such as valence changes, elemental dissolution, structural reconfiguration, and active site poisoning and propose targeted strategies for improvement, including doping, alloying, and substrate engineering. Additionally, advancements in electrode design, such as structural modifications and membrane enhancements, are highlighted for their role in improving stability. Operational parameters such as temperature, pressure, and electrolyte composition also play crucial roles in extending the lifespan of the reaction. By addressing these diverse factors, this review aims to offer a deeper understanding of the determinants of long-term stability in the CO2RR, laying the groundwork for the development of robust, scalable technologies for efficient carbon dioxide conversion.

Switching CO2 Electroreduction toward C2+ Products and CH4 by Regulating the Dimerization and Protonation in Platinum/Copper Catalysts

Copper (Cu)-based catalysts exhibit distinctive performance in the electrochemical CO2 reduction reaction (CO2RR) with complex mechanism and sophisticated types of products. The management of key intermediates *CO and *H is a necessary factor for achieving high product selectivity, but lack of efficient and versatile strategies. Herein, we designed Pt modified Cu catalysts to effectively modulate the competitive coverage of those intermediates. The Pt single-atoms and Pt nanoparticles modified Cu catalysts (denoted as Cu-Pt1 and Cu-PtNPs) precisely regulated the protonation and dimerization, with the faradaic efficiency (FE) of C2+ products up to 70.4 % and the FE of CH4 reaching 57.7 %, respectively. CO stripping experiments reveal that Pt1 sites could enhance the adsorption of *CO, while PtNPs exhibit *CO tolerance for H2O dissociation. In situ spectroscopic results further confirms that high coverage of *CO is achieved on Cu-Pt1, while *CHO on Cu-PtNPs might generate by additional water dissociation. As elucidated by theoretical studies, the interfacial sites of Cu-Pt1 would favor the *CO coverage promoting the evolution of *OCCO for C2+ products while PtNPs supplementarily accelerate H2O dissociation achieving *CHO for CH4. This work provides insights for efficient and targeted CO2 conversion by atomically design of active sites with engineered key intermediates coverage.

Progress in Cu-Based Catalyst Design for Sustained Electrocatalytic CO2 to C2+ Conversion

The electrocatalytic conversion of CO2 into valuable multi-carbon (C2+) products using Cu-based catalysts has attracted significant attention. This review provides a comprehensive overview of recent advances in Cu-based catalyst design to improve C2+ selectivity and operational stability. It begins with an analysis of the fundamental reaction pathways for C2+ formation, encompassing both established and emerging mechanisms, which offer critical insights for catalyst design. In situ techniques, essential for validating these pathways by real-time observation of intermediates and material evolution, are also introduced. A key focus of this review is placed on how to enhance C2+ selectivity through intermediates manipulation, particularly emphasizing catalytic site construction to promote C─C coupling via increasing *CO coverage and optimizing protonation. Additionally, the challenge of maintaining catalytic activity under reaction conditions is discussed, highlighting the reduction of active charged Cu species and materials reconstruction as major obstacles. To address these, the review describes recent strategies to preserve active sites and control materials evolution, including novel catalyst design and the utilization and mitigation of reconstruction. By presenting these developments and the challenges ahead, this review aims to guide future materials design for CO2 conversion.

Electrochemical CO2 Reduction in Acidic Media: A Perspective

The electrochemical CO2 reduction reaction (eCO2RR) is a promising approach for converting CO2 to useful chemicals and, hence, achieving carbon neutrality. Though high selectivity and activity of products have been achieved recently, all are reported in neutral or alkaline electrolytes. Although these electrolyte media give high selectivity and activity, they face the major challenge of low CO2 utilization because of carbonate formation, which lowers the overall efficiency of the process. Conducting the eCO2RR in acidic media can help overcome the issue of carbonate formation and hence can increase the CO2 utilization efficiency. However, there are many challenges associated with acidic eCO2RR. Two major concerns are the highly competitive hydrogen evolution reaction in acidic media and salt precipitation issues. This Perspective focuses on the fundamentals of acidic eCO2RR, recent catalyst development strategies, and relevant problems that need to be addressed in the future. In the end, we provide a future outlook that will give an idea about the problems to focus on in the future in the field of acidic eCO2RR.

Electrochemical CO2 reduction to liquid fuels: Mechanistic pathways and surface/interface engineering of catalysts and electrolytes

The high energy density of green synthetic liquid chemicals and fuels makes them ideal for sustainable energy storage and transportation applications. Electroreduction of carbon dioxide (CO2) directly into such high value-added chemicals can help us achieve a renewable C cycle. Such electrochemical reduction typically suffers from low faradaic efficiencies (FEs) and generates a mixture of products due to the complexity of controlling the reaction selectivity. This perspective summarizes recent advances in the mechanistic understanding of CO2 reduction reaction pathways toward liquid products and the state-of-the-art catalytic materials for conversion of CO2 to liquid C1 (e.g., formic acid, methanol) and C2+ products (e.g., acetic acid, ethanol, n-propanol). Many liquid fuels are being produced with FEs between 80% and 100%. We discuss the use of structure-binding energy relationships, computational screening, and machine learning to identify promising candidates for experimental validation. Finally, we classify strategies for controlling catalyst selectivity and summarize breakthroughs, prospects, and challenges in electrocatalytic CO2 reduction to guide future developments.

Structural Transformation and Degradation of Cu Oxide Nanocatalysts during Electrochemical CO2 Reduction

The electrochemical CO2 reduction reaction (CO2RR) holds enormous potential as a carbon-neutral route to the sustainable production of fuels and platform chemicals. The durability for long-term operation is currently inadequate for commercialization, however, and the underlying deactivation process remains elusive. A fundamental understanding of the degradation mechanism of electrocatalysts, which can dictate the overall device performance, is needed. In this work, we report the structural dynamics and degradation pathway of Cu oxide nanoparticles (CuOx NPs) during the CO2RR by using in situ small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS). The in situ SAXS reveals a reduction in the size of NPs when subjected to a potential at which no reaction products are detected. At potentials where the CO2RR starts to occur, CuOx NPs are agglomerated through a particle migration and coalescence process in the early stage of the reaction, followed by Ostwald ripening (OR) as the dominant degradation mechanism for the remainder of the reaction. As the applied potential becomes more negative, the OR process becomes more dominant, and for the most negative applied potential, OR dominates for the entire reaction time. The morphological changes are linked to a gradual decrease in the formation rate for multicarbon products (C2H4 and ethanol). Other reaction parameters, including reaction intermediates and local high pH, induce changes in the agglomeration process and final morphology of the CuOx NPs electrode, supported by post-mortem ex situ microscopic analysis. The in situ XAS analysis suggests that the CuOx NPs reduced into the metallic state before the structural transformation was observed. The introduction of high surface area carbon supports with ionomer coating mitigates the degree of structural transformation and detachment of the CuOx NPs electrode. These findings show the dynamic nature of Cu nanocatalysts during the CO2RR and can serve as a rational guideline toward a stable catalyst system under electrochemical conditions.

Advanced systems for enhanced CO2 electroreduction

Carbon dioxide (CO2) electroreduction has extraordinary significance in curbing CO2 emissions while simultaneously producing value-added chemicals with economic and environmental benefits. In recent years, breakthroughs in designing catalysts, optimizing intrinsic activity, developing reactors, and elucidating reaction mechanisms have continuously driven the advancement of CO2 electroreduction. However, the industrialization of CO2 electroreduction remains a challenging task, with high energy consumption, high costs, limited reaction products, and restricted application scenarios being the issues that urgently need to be addressed. To accelerate the progress of CO2 electroreduction towards practical application, this review shifts the research focus from catalysts to aspects such as reactions and systems, aiming to improve reaction efficiency, reduce technical costs, expand the range of products, and enhance selectivity, offering readers a new perspective. In particular, innovative and specific design strategies such as CO2 reduction coupled with alternative oxidation, co-reduction reaction of CO2 and C/N/O/S-containing species, cascade systems, and integrated CO2 capture and reduction systems are discussed in detail. Additionally, personal views on the opportunities and future challenges of the aforementioned innovative strategies are provided, offering new insights for the future research and development of CO2 electroreduction.

Facilitating Oriented Electron Transfer from Cu to Mo2C MXene for Weakened Mo─H Bond Toward Enhanced Photocatalytic H2 Generation

Mo2C MXene (Mo2CTx) is recognized as an excellent cocatalyst due to unique physicochemical properties and platinum-like d-band of Mo active sites. However, Mo sites of Mo2CTx with high-density empty d-orbitals exhibit strong Mo─Hads bonds during photocatalytic hydrogen evolution, leading to easy adsorption of hydrogen ions from solution and unfavorable desorption of H2 from Mo sites. To weaken the Mo─Hads bond, a strategy of oriented electron transfer from Cu to Mo2CTx to increase the antibonding orbital occupancy of Mo─Hads hybrid orbitals is implemented by introducing Cu into Mo2CTx interlayers to form Cu-Mo2CTx. The Cu-Mo2CTx is synthesized from Mo2Ga2C and CuCl2 via a one-step molten salt method and combined with TiO2 to form Cu-Mo2CTx/TiO2 photocatalyst through an ultrasound-assisted approach. Hydrogen production tests reveal that an exceptional performance of Cu-Mo2CTx/TiO2 (6446 µmol h-1 g-1, AQE = 18.3%) is 8.4 fold higher than that of Mo2CF2/TiO2 (Mo2CF2 by the conventional etchant NH4F+HCl). Density functional theory (DFT) calculations and characterization results corroborate that the oriented electron transfer from Cu to Mo2CTx increases the Mo─Hads antibonding occupancy in Cu-Mo2CTx, thereby weakening Mo─Hads bonds and accelerating the hydrogen evolution rate of TiO2. This research offers valuable insights into optimizing H-adsorption capabilities at active sites on MXene materials.

Synthesis of Closely-Contacted Cu2O-CoWO4 Nanosheet Composites for Cuproptosis Therapy to Tumors With Sonodynamic and Photothermal Assistance

Cuproptosis offers a promising and selective therapeutic strategy for cancer therapy. To fully realize its potential, the development of novel cuproptosis therapeutic agents and the achievement of efficient copper release are critical steps forward. Herein, closely-contacted Cu2O-CoWO4 nanosheet heterojunctions (CCW-NH) are successfully synthesized using an in-situ process for cuproptosis therapy. The efficient release of copper ions from CCW-NH can be triggered by ultrasound irradiation, primarily due to the generation of superoxide radicals as the sonodynamic agents via the Z-scheme charge transfer mechanism. When subjected to the combined effects of ultrasound and laser irradiation, the effective release of copper ions is increased by 1.7 times compared to the untreated group, significantly enhancing the efficiency of cuproptosis. And the incorporation of CCW-NH and L-arginine into the temperature-sensitive injectable hydrogel (HP-CCW@LA) ultimately achieved a tumor inhibition rate of up to 95.1%. L-arginine, serving as a reducing agent, enabled the sustained release of highly active Cu+ during treatment. Notably, after treating tumors with HP-CCW@LA, the tumor microenvironment is leveraged to promote copper ion conversion, which offers the potential for monitoring tumor therapy efficacy through magnetic resonance imaging. This work offers a novel integrated strategy for the development of new cuproptosis agents and therapeutic evaluation.

State of Play of Critical Mineral-Based Catalysts for Electrochemical E-Refinery to Synthetic Fuels

The pursuit of decarbonization involves leveraging waste CO2 for the production of valuable fuels and chemicals (e.g., ethanol, ethylene, and urea) through the electrochemical CO2 reduction reactions (CO2RR). The efficacy of this process heavily depends on electrocatalyst performance, which is generally reliant on high loading of critical minerals. However, the supply of these minerals is susceptible to shortage and disruption, prompting concerns regarding their usage, particularly in electrocatalysis, requiring swift innovations to mitigate the supply risks. The reliance on critical minerals in catalyst fabrication can be reduced by implementing design strategies that improve the available active sites, thereby increasing the mass activity. This review seeks to discuss and analyze potential strategies, challenges, and opportunities for improving catalyst activity in CO2RR with a special attention to addressing the risks associated with critical mineral scarcity. By shedding light onto these aspects of critical mineral-based catalyst systems, this review aims to inspire the development of high-performance catalysts and facilitates the practical application of CO2RR technology, whilst mitigating adverse economic, environmental, and community impacts.

Recent advancements in carbon/metal-based nano-catalysts for the reduction of CO2 to value-added products

Due to the increased human activities in burning of fossil fuels and deforestation, the CO2 level in the atmosphere gets increased up to 415 ppm; although it is an essential component for plant growth, an increased level of CO2 in the atmosphere leads to global warming and catastrophic climate change. Various conventional methods are used to capture and utilize CO2, among that a feasible and eco-friendly technique for creating value-added products is the CO2RR. Photochemical, electrochemical, thermochemical, and biochemical approaches can be used to decrease the level of CO2 in the atmosphere. The introduction of nano-catalysts in the reduction process helps in the efficient conversion of CO2 with improved selectivity, increased efficiency, and also enhanced stability of the catalyst materials. Thus, in this mini-review of nano-catalysts, some of the products formed during the reduction process, like CH3OH, C2H5OH, CO, HCOOH, and CH4, are explained. Among different types of metal catalysts, carbonaceous, single-atom catalysts, and MOF based catalysts play a significant role in the CO2 RR process. The effects of the catalyst material on the surface area, composition, and structural alterations are covered in depth. To aid in the design and development of high-performance nano-catalysts for value-added products, the current state, difficulties, and future prospects are provided.

Energy-efficient CO(2) conversion to multicarbon products at high rates on CuGa bimetallic catalyst

Electrocatalytic CO2 reduction to multi-carbon products is a promising approach for achieving carbon-neutral economies. However, the energy efficiency of these processes remains low, particularly at high current densities. Herein, we demonstrate that the low energy efficiencies are, in part, sometimes significantly, attributed to the high concentration overpotential resulting from the instability (i.e., flooding) of catalyst-layer during electrolysis. To tackle this challenge, we develop copper/gallium bimetallic catalysts with reduced activation energies for the formation of multi-carbon products. Consequently, the reduced activation overpotential allows us to achieve practical-relevant current densities for CO2 reduction at low cathodic potentials, ensuring good stability of the catalyst-layer and thereby minimizing the undesired concentration overpotential. The optimized bimetallic catalyst achieves over 50% cathodic energy efficiency for multi-carbon production at a high current density of over 1.0 A cm - 2 . Furthermore, we achieve current densities exceeding 2.0 A cm - 2 in a zero-gap membrane-electrode-assembly reactor, with a full-cell energy efficiency surpassing 30%.

Site-Selective Growth of fcc-2H-fcc Copper on Unconventional Phase Metal Nanomaterials for Highly Efficient Tandem CO2 Electroreduction

Copper (Cu) nanomaterials are a unique kind of electrocatalysts for high-value multi-carbon production in carbon dioxide reduction reaction (CO2RR), which holds enormous potential in attaining carbon neutrality. However, phase engineering of Cu nanomaterials remains challenging, especially for the construction of unconventional phase Cu-based asymmetric heteronanostructures. Here the site-selective growth of Cu on unusual phase gold (Au) nanorods, obtaining three kinds of heterophase fcc-2H-fcc Au-Cu heteronanostructures is reported. Significantly, the resultant fcc-2H-fcc Au-Cu Janus nanostructures (JNSs) break the symmetric growth mode of Cu on Au. In electrocatalytic CO2RR, the fcc-2H-fcc Au-Cu JNSs exhibit excellent performance in both H-type and flow cells, with Faradaic efficiencies of 55.5% and 84.3% for ethylene and multi-carbon products, respectively. In situ characterizations and theoretical calculations reveal the co-exposure of 2H-Au and 2H-Cu domains in Au-Cu JNSs diversifies the CO* adsorption configurations and promotes the CO* spillover and subsequent C-C coupling toward ethylene generation with reduced energy barriers.

Toward Durable CO2 Electroreduction with Cu-Based Catalysts via Understanding Their Deactivation Modes

The technology of CO2 electrochemical reduction (CO2ER) provides a means to convert CO2, a waste greenhouse gas, into value-added chemicals. Copper is the most studied element that is capable of catalyzing CO2ER to obtain multicarbon products, such as ethylene, ethanol, acetate, etc., at an appreciable rate. Under the operating condition of CO2ER, the catalytic performance of Cu decays because of several factors that alters the surface properties of Cu. In this review, these factors that cause the degradation of Cu-based CO2ER catalysts are categorized into generalized deactivation modes, that are applicable to all electrocatalytic systems. The fundamental principles of each deactivation mode and the associated effects of each on Cu-based catalysts are discussed in detail. Structure- and composition-activity relationship developed from recent in situ/operando characterization studies are presented as evidence of related deactivation modes in operation. With the aim to address these deactivation modes, catalyst design and reaction environment engineering rationales are suggested. Finally, perspectives and remarks built upon the recent advances in CO2ER are provided in attempts to improve the durability of CO2ER catalysts.

Alloying and confinement effects on hierarchically nanoporous CuAu for efficient electrocatalytic semi-hydrogenation of terminal alkynes

Electrocatalytic alkynes semi-hydrogenation to produce alkenes with high yield and Faradaic efficiency remains technically challenging because of kinetically favorable hydrogen evolution reaction and over-hydrogenation. Here, we propose a hierarchically nanoporous Cu50Au50 alloy to improve electrocatalytic performance toward semi-hydrogenation of alkynes. Using Operando X-ray absorption spectroscopy and density functional theory calculations, we find that Au modulate the electronic structure of Cu, which could intrinsically inhibit the combination of H* to form H2 and weaken alkene adsorption, thus promoting alkyne semi-hydrogenation and hampering alkene over-hydrogenation. Finite element method simulations and experimental results unveil that hierarchically nanoporous catalysts induce a local microenvironment with abundant K+ cations by enhancing the electric field within the nanopore, accelerating water electrolysis to form more H*, thereby promoting the conversion of alkynes. As a result, the nanoporous Cu50Au50 electrocatalyst achieves highly efficient electrocatalytic semi-hydrogenation of alkynes with 94% conversion, 100% selectivity, and a 92% Faradaic efficiency over wide potential window. This work provides a general guidance of the rational design for high-performance electrocatalytic transfer semi-hydrogenation catalysts.

Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids

The electrocatalytic CO2 reduction reaction (CO2RR) is a sustainable route for converting CO2 into value-added fuels and feedstocks, advancing a carbon-neutral economy. The electrolyte critically influences CO2 utilization, reaction rate and product selectivity. While typically conducted in neutral/alkaline aqueous electrolytes, the CO2RR faces challenges due to (bi)carbonate formation and its crossover to the anolyte, reducing efficiency and stability. Acidic media offer promise by suppressing these processes, but the low Faradaic efficiency, especially for multicarbon (C2+) products, and poor electrocatalyst stability persist. The effective regulation of the reaction environment at the cathode is essential to favor the CO2RR over the competitive hydrogen evolution reaction (HER) and improve long-term stability. This review examines progress in the acidic CO2RR, focusing on reaction environment regulation strategies such as electrocatalyst design, electrode modification and electrolyte engineering to promote the CO2RR. Insights into the reaction mechanisms via in situ/operando techniques and theoretical calculations are discussed, along with critical challenges and future directions in acidic CO2RR technology, offering guidance for developing practical systems for the carbon-neutral community.

Alkali cation-induced cathodic corrosion in Cu electrocatalysts

The reconstruction of Cu catalysts during electrochemical reduction of CO2 is a widely known but poorly understood phenomenon. Herein, we examine the structural evolution of Cu nanocubes under CO2 reduction reaction and its relevant reaction conditions using identical location transmission electron microscopy, cyclic voltammetry, in situ X-ray absorption fine structure spectroscopy and ab initio molecular dynamics simulation. Our results suggest that Cu catalysts reconstruct via a hitherto unexplored yet critical pathway - alkali cation-induced cathodic corrosion, when the electrode potential is more negative than an onset value (e.g., -0.4 VRHE when using 0.1 M KHCO3). Having alkali cations in the electrolyte is critical for such a process. Consequently, Cu catalysts will inevitably undergo surface reconstructions during a typical process of CO2 reduction reaction, resulting in dynamic catalyst morphologies. While having these reconstructions does not necessarily preclude stable electrocatalytic reactions, they will indeed prohibit long-term selectivity and activity enhancement by controlling the morphology of Cu pre-catalysts. Alternatively, by operating Cu catalysts at less negative potentials in the CO electrochemical reduction, we show that Cu nanocubes can provide a much more stable selectivity advantage over spherical Cu nanoparticles.

Advances and challenges in the electrochemical reduction of carbon dioxide

The electrocatalytic carbon dioxide reduction reaction (ECO2RR) is a promising way to realize the transformation of waste into valuable material, which can not only meet the environmental goal of reducing carbon emissions, but also obtain clean energy and valuable industrial products simultaneously. Herein, we first introduce the complex CO2RR mechanisms based on the number of carbons in the product. Since the coupling of C-C bonds is unanimously recognized as the key mechanism step in the ECO2RR for the generation of high-value products, the structural-activity relationship of electrocatalysts is systematically reviewed. Next, we comprehensively classify the latest developments, both experimental and theoretical, in different categories of cutting-edge electrocatalysts and provide theoretical insights on various aspects. Finally, challenges are discussed from the perspectives of both materials and devices to inspire researchers to promote the industrial application of the ECO2RR at the earliest.

Electronic Structure Design of Transition Metal-Based Catalysts for Electrochemical Carbon Dioxide Reduction

With the increasingly serious greenhouse effect, the electrochemical carbon dioxide reduction reaction (CO2RR) has garnered widespread attention as it is capable of leveraging renewable energy to convert CO2 into value-added chemicals and fuels. However, the performance of CO2RR can hardly meet expectations because of the diverse intermediates and complicated reaction processes, necessitating the exploitation of highly efficient catalysts. In recent years, with advanced characterization technologies and theoretical simulations, the exploration of catalytic mechanisms has gradually deepened into the electronic structure of catalysts and their interactions with intermediates, which serve as a bridge to facilitate the deeper comprehension of structure-performance relationships. Transition metal-based catalysts (TMCs), extensively applied in electrochemical CO2RR, demonstrate substantial potential for further electronic structure modulation, given their abundance of d electrons. Herein, we discuss the representative feasible strategies to modulate the electronic structure of catalysts, including doping, vacancy, alloying, heterostructure, strain, and phase engineering. These approaches profoundly alter the inherent properties of TMCs and their interaction with intermediates, thereby greatly affecting the reaction rate and pathway of CO2RR. It is believed that the rational electronic structure design and modulation can fundamentally provide viable directions and strategies for the development of advanced catalysts toward efficient electrochemical conversion of CO2 and many other small molecules.

Customizing catalyst surface/interface structures for electrochemical CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) provides a promising route to converting CO2 into value-added chemicals and to neutralizing the greenhouse gas emission. For the industrial application of CO2RR, high-performance electrocatalysts featuring high activities and selectivities are essential. It has been demonstrated that customizing the catalyst surface/interface structures allows for high-precision control over the microenvironment for catalysis as well as the adsorption/desorption behaviors of key reaction intermediates in CO2RR, thereby elevating the activity, selectivity and stability of the electrocatalysts. In this paper, we review the progress in customizing the surface/interface structures for CO2RR electrocatalysts (including atomic-site catalysts, metal catalysts, and metal/oxide catalysts). From the perspectives of coordination engineering, atomic interface design, surface modification, and hetero-interface construction, we delineate the resulting specific alterations in surface/interface structures, and their effect on the CO2RR process. At the end of this review, we present a brief discussion and outlook on the current challenges and future directions for achieving high-efficiency CO2RR via surface/interface engineering.

Recent advanced strategies for bimetallenes toward electrocatalytic energy conversion reactions

Designing low-dimensional nanomaterials is vital to address the energy and environmental crisis by means of electrocatalytic conversion reactions. Bimetallenes, as an emerging class of 2D materials, present promise for electrocatalytic conversion reactions. By leveraging atomically thin layers, bimetallenes present unsaturated surface coordination, high specific surface area and high conductivity, which are all indispensable features for heterogeneous electrochemical reactions. However, the intrinsic activity and stability of bimetallenes needs to be improved further for bimetallene electrocatalysts, due to the higher demands of practical applications. Recently, many strategies have been developed to optimize the chemical or electronic structure to accommodate transfer of reactants, adsorption or desorption of intermediates, and dissociation of products. Considering that most such work focuses on adjusting the structure, this review offers in-depth insight into recent representative strategies for optimizing bimetallene electrocatalysts, mainly including alloying, strain effects, ligand effects, defects and heteroatom doping. Moreover, by summarizing the performance of bimetallenes optimized using various strategies, we provide a means to understand structure-property relationships. In addition, future prospects and challenges are discussed for further development of bimetallene electrocatalysts.

Surface engineering for stable electrocatalysis

In recent decades, significant progress has been achieved in rational developments of electrocatalysts through constructing novel atomistic structures and modulating catalytic surface topography, realizing substantial enhancement in electrocatalytic activities. Numerous advanced catalysts were developed for electrochemical energy conversion, exhibiting low overpotential, high intrinsic activity, and selectivity. Yet, maintaining the high catalytic performance under working conditions with high polarization and vigorous microkinetics that induce intensive degradation of surface nanostructures presents a significant challenge for commercial applications. Recently, advanced operando and computational techniques have provided comprehensive mechanistic insights into the degradation of surficial functional structures. Additionally, various innovative strategies have been devised and proven effective in sustaining electrocatalytic activity under harsh operating conditions. This review aims to discuss the most recent understanding of the degradation microkinetics of catalysts across an entire range of anodic to cathodic polarizations, encompassing processes such as oxygen evolution and reduction, hydrogen reduction, and carbon dioxide reduction. Subsequently, innovative strategies adopted to stabilize the materials' structure and activity are highlighted with an in-depth discussion of the underlying rationale. Finally, we present conclusions and perspectives regarding future research and development. By identifying the research gaps, this review aims to inspire further exploration of surface degradation mechanisms and rational design of durable electrocatalysts, ultimately contributing to the large-scale utilization of electroconversion technologies.

Multiscale effects in tandem CO2 electrolysis to C2+ products

CO2 electrolysis is a sustainable technology capable of accelerating global decarbonisation through the production of high-value alternatives to fossil-derived products. CO2 conversion can generate critical multicarbon (C2+) products such as drop-in chemicals ethylene and ethanol, however achieving high selectivity from single-component catalysts is often limited by the competitive formation of C1 products. Tandem catalysis can overcome C2+ selectivity limitations through the incorporation of a component that generates a high concentration of CO, the primary reactant involved in the C-C coupling step to form C2+ products. A wide range of approaches to promote tandem CO2 electrolysis have been presented in recent literature that span atomic-scale manipulation to device-scale engineering. Therefore, an understanding of multiscale effects that contribute to selectivity alterations are required to develop effective tandem systems. In this review, we use relevant examples to highlight the complex and interlinked contributions to selectivity and provide an outlook for future development of tandem CO2 electrolysis systems.

Cooperative adsorption of interfacial Ga-N dual-site in GaOOH@N-doped carbon nanotubes for enhanced electrocatalytic reduction of carbon dioxide

To reduce activation energy barrier and promote the kinetics of electrocatalytic CO2 reduction reaction (eCO2RR), the performance of CO2 adsorption and activation on electrocatalysts should be optimized. Here, GaOOH is successfully coupled with N-doped carbon nanotubes (NC) via a facile self-assembly-calcination process. The obtained GaOOH@N-doped carbon nanotubes (Ga-NC) display the best CO faradaic efficiency of 96.1 % at -0.6 V (vs. reversible hydrogen electrode). Control-experiment and characterization results suggest Ga-N dual-site in interface between GaOOH and NC shows cooperative adsorption of CO2. C atom in CO2 is adsorbed on N site while O atom in CO2 is adsorbed on Ga site. This cooperative adsorption efficiently promotes the CO2 adsorption and activation performance, as well as the breaking of CO bond due to opposite attraction from Ga-N dual-site. Moreover, in-situ Fourier transform infrared spectroscopy confirms decreased reaction barrier for formation of *CO2- and *COOH intermediates. This work inspires us to construct interfacial dual-site structure with cooperative adsorption property for promoting eCO2RR activity.

High-Power CO2-to-C2 Electroreduction on Ga-Spaced, Square-like Cu Sites

The electrochemical conversion of CO2 into multicarbon (C2) products on Cu-based catalysts is strongly affected by the surface coverage of adsorbed CO (*CO) intermediates and the subsequent C-C coupling. However, the increased *CO coverage inevitably leads to strong *CO repulsion and a reduced C-C coupling efficiency, thus resulting in suboptimal CO2-to-C2 activity and selectivity, especially at ampere-level electrolysis current densities. Herein, we developed an atomically ordered Cu9Ga4 intermetallic compound consisting of Cu square-like binding sites interspaced by catalytically inert Ga atoms. Compared to Cu(100) previously known with a high C2 selectivity, the Ga-spaced, square-like Cu sites presented an elongated Cu-Cu distance that allowed to reduce *CO repulsion and increased *CO coverage simultaneously, thus endowing more efficient C-C coupling to C2 products than Cu(100) and Cu(111). The Cu9Ga4 catalyst exhibited an outstanding CO2-to-C2 electroreduction, with a peak C2 partial current density of 1207 mA cm-2 and a corresponding Faradaic efficiency of 71%. Moreover, the Cu9Ga4 catalyst demonstrated a high-power (∼200 W) electrolysis capability with excellent electrochemical stability.

Stability Issues in Electrochemical CO2 Reduction: Recent Advances in Fundamental Understanding and Design Strategies

Electrochemical CO2 reduction reaction (CO2 RR) offers a promising approach to close the anthropogenic carbon cycle and store intermittent renewable energy in fuels or chemicals. On the path to commercializing this technology, achieving the long-term operation stability is a central requirement but still confronts challenges. This motivates to organize the present review to systematically discuss the stability issue of CO2 RR. This review starts from the fundamental understanding on the destabilization mechanisms of CO2 RR, with focus on the degradation of electrocatalyst and change of reaction microenvironment during continuous electrolysis. Subsequently, recent efforts on catalyst design to stabilize the active sites are summarized, where increasing atomic binding strength to resist surface reconstruction is highlighted. Next, the optimization of electrolysis system to enhance the operation stability by maintaining reaction microenvironment especially mitigating flooding and carbonate problems is demonstrated. The manipulation on operation conditions also enables to prolong CO2 RR lifespan through recovering catalytically active sites and mass transport process. This review finally ends up by indicating the challenges and future opportunities.

Voltage-Driven Chemical Reactions Enable the Synthesis of Tunable Liquid Ga-Metal Nanoparticles

Nanosized particles of liquid metals are emerging materials that hold promise for applications spanning from microelectronics to catalysis. Yet, knowledge of their chemical reactivity is largely unknown. Here, we study the reactivity of liquid Ga and Cu nanoparticles under the application of a cathodic voltage. We discover that the applied voltage and the spatial proximity of these two particle precursors dictate the reaction outcome. In particular, we find that a gradual voltage ramp is crucial to reduce the native oxide skin of gallium and enable reactive wetting between the Ga and Cu nanoparticles; instead, a voltage step causes dewetting between the two. We determine that the use of liquid Ga/Cu nanodimer precursors, which consist of an oxide-covered Ga domain interfaced with a metallic Cu domain, provides a more uniform mixing and results in more homogeneous reaction products compared to a physical mixture of Ga and Cu NPs. Having learned this, we obtain CuGa2 alloys or solid@liquid CuGa2@Ga core@shell nanoparticles by tuning the stoichiometry of Ga and Cu in the nanodimer precursors. These products reveal an interesting complementarity of thermal and voltage-driven syntheses to expand the compositional range of bimetallic NPs. Finally, we extend the voltage-driven synthesis to the combination of Ga with other elements (Ag, Sn, Co, and W). By rationalizing the impact of the native skin reduction rate, the wetting properties, and the chemical reactivity between Ga and other metals on the results of such voltage-driven chemical manipulation, we define the criteria to predict the outcome of this reaction and set the ground for future studies targeting various applications for multielement nanomaterials based on liquid Ga.

Oxophilicity-Controlled CO2 Electroreduction to C2+ Alcohols over Lewis Acid Metal-Doped Cuδ+ Catalysts

Cu-based electrocatalysts have great potential for facilitating CO2 reduction to produce energy-intensive fuels and chemicals. However, it remains challenging to obtain high product selectivity due to the inevitable strong competition among various pathways. Here, we propose a strategy to regulate the adsorption of oxygen-associated active species on Cu by introducing an oxophilic metal, which can effectively improve the selectivity of C2+ alcohols. Theoretical calculations manifested that doping of Lewis acid metal Al into Cu can affect the C-O bond and Cu-C bond breaking toward the selectively determining intermediate (shared by ethanol and ethylene), thus prioritizing the ethanol pathway. Experimentally, the Al-doped Cu catalyst exhibited an outstanding C2+ Faradaic efficiency (FE) of 84.5% with remarkable stability. In particular, the C2+ alcohol FE could reach 55.2% with a partial current density of 354.2 mA cm-2 and a formation rate of 1066.8 μmol cm-2 h-1. A detailed experimental study revealed that Al doping improved the adsorption strength of active oxygen species on the Cu surface and stabilized the key intermediate *OC2H5, leading to high selectivity toward ethanol. Further investigation showed that this strategy could also be extended to other Lewis acid metals.

Why surface hydrophobicity promotes CO2 electroreduction: a case study of hydrophobic polymer N-heterocyclic carbenes

We report the use of polymer N-heterocyclic carbenes (NHCs) to control the microenvironment surrounding metal nanocatalysts, thereby enhancing their catalytic performance in CO2 electroreduction. Three polymer NHC ligands were designed with different hydrophobicity: hydrophilic poly(ethylene oxide) (PEO-NHC), hydrophobic polystyrene (PS-NHC), and amphiphilic block copolymer (BCP) (PEO-b-PS-NHC). All three polymer NHCs exhibited enhanced reactivity of gold nanoparticles (AuNPs) during CO2 electroreduction by suppressing proton reduction. Notably, the incorporation of hydrophobic PS segments in both PS-NHC and PEO-b-PS-NHC led to a twofold increase in the partial current density for CO formation, as compared to the hydrophilic PEO-NHC. While polymer ligands did not hinder ion diffusion, their hydrophobicity altered the localized hydrogen bonding structures of water. This was confirmed experimentally and theoretically through attenuated total reflectance surface-enhanced infrared absorption spectroscopy and molecular dynamics simulation, demonstrating improved CO2 diffusion and subsequent reduction in the presence of hydrophobic polymers. Furthermore, NHCs exhibited reasonable stability under reductive conditions, preserving the structural integrity of AuNPs, unlike thiol-ended polymers. The combination of NHC binding motifs with hydrophobic polymers provides valuable insights into controlling the microenvironment of metal nanocatalysts, offering a bioinspired strategy for the design of artificial metalloenzymes.