Electrochemical CO2 Reduction to Formic Acid at Low Overpotential and with High Faradaic Efficiency on Carbon-Supported Bimetallic Pd–Pt Nanoparticles

Cu3N Nanocubes for Selective Electrochemical Reduction of CO2 to Ethylene

Understanding the Cu-catalyzed electrochemical CO₂ reduction reaction (CO₂RR) under ambient conditions is both fundamentally interesting and technologically important for selective CO₂RR to hydrocarbons. Current Cu catalysts studied for the CO₂RR can show high activity but tend to yield a mixture of different hydrocarbons, posing a serious challenge on using any of these catalysts for selective CO₂RR. Here, we report a new perovskite-type copper(I) nitride (Cu₃N) nanocube (NC) catalyst for selective CO₂RR. The 25 nm Cu₃N NCs show high CO₂RR selectivity and stability to ethylene (C₂H₄) at -1.6 V (vs reversible hydrogen electrode (RHE)) with the Faradaic efficiency of 60%, mass activity of 34 A/g, and C₂H₄/CH₄ molar ratio of >2000. More detailed electrochemical characterization, X-ray photon spectroscopy, and density functional theory calculations suggest that the high CO₂RR selectivity is likely a result of (100) Cu(I) stabilization by the Cu₃N structure, which favors CO-CHO coupling on the (100) Cu₃N surface, leading to selective formation of C₂H₄. Our study presents a good example of utilizing metal nitrides as highly efficient nanocatalysts for selective CO₂RR to hydrocarbons that will be important for sustainable chemistry/energy applications.

Operando Insight into the Correlation between the Structure and Composition of CuZn Nanoparticles and Their Selectivity for the Electrochemical CO2 Reduction

Bimetallic CuZn catalysts have been recently proposed as alternatives in order to achieve selectivity control during the electrochemical reduction of CO₂ (CO₂RR). However, fundamental understanding of the underlying reaction mechanism and parameters determining the CO₂RR performance is still missing. In this study, we have employed size-controlled (∼5 nm) Cu_100–xZn_x nanoparticles (NPs) supported on carbon to investigate the correlation between their structure and composition and catalytic performance. By tuning the concentration of Zn, a drastic increase in CH₄ selectivity [∼70% Faradaic efficiency (F.E.)] could be achieved for Zn contents from 10 to 50, which was accompanied by a suppression of the H₂ production. Samples containing a higher Zn concentration displayed significantly lower CH₄ production and an abrupt switch in the selectivity to CO. Lack of metal leaching was observed based on quasi in situ X-ray photoelectron spectroscopy (XPS). Operando X-ray absorption fine structure (XAFS) spectroscopy measurements revealed that the alloying of Cu atoms with Zn atoms takes place under reaction conditions and plays a determining role in the product selectivity. Time-dependent XAFS analysis showed that the local structure and chemical environment around the Cu atoms continuously evolve during CO₂RR for several hours. In particular, cationic Zn species initially present were found to get reduced as the reaction proceeded, leading to the formation of a CuZn alloy (brass). The evolution of the Cu–Zn interaction with time during CO₂RR was found to be responsible for the change in the selectivity from CH₄ over Cu-ZnO NPs to CO over CuZn alloy NPs. This study highlights the importance of having access to in depth information on the interplay between the different atomic species in bimetallic NP electrocatalysts under operando reaction conditions in order to understand and ultimately tune their reactivity.

Electrochemical Behavior of Carbon Electrodes for In Situ Redox Studies in a Transmission Electron Microscope

Electrochemical liquid cell transmission electron microscopy (TEM) is a unique technique for probing nanocatalyst behavior during operation for a range of different electrocatalytic processes, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), or electrochemical CO2 reduction (eCO2R). A major challenge to the technique's applicability to these systems has to do with the choice of substrate, which requires a wide inert potential range for quantitative electrochemistry, and is also responsible for minimizing background gas generation in the confined microscale environment. Here, we report on the feasibility of electrochemical experiments using the standard redox couple Fe(CN)63-/4- and microchips featuring carbon-coated electrodes. We electrochemically assess the in situ performance with respect to flow rate, liquid volume, and scan rate. Equally important with the choice of working substrate is the choice of the reference electrode. We demonstrate that the use of a modified electrode setup allows for potential measurements relatable to bulk studies. Furthermore, we use this setup to demonstrate the inert potential range for carbon-coated electrodes in aqueous electrolytes for HER, OER, ORR, and eCO2R. This work provides a basis for understanding electrochemical measurements in similar microscale systems and for studying gas-generating reactions with liquid electrochemical TEM.

Electrolyte Effects on the Electrochemical Reduction of CO2

The electrochemical reduction of CO2 to fuels or commodity chemicals is a reaction of high interest for closing the anthropogenic carbon cycle. The role of the electrolyte is of particular interest, as the interplay between the electrocatalytic surface and the electrolyte plays an important role in determining the outcome of the CO2 reduction reaction. Therefore, insights on electrolyte effects on the electrochemical reduction of CO2 are pivotal in designing electrochemical devices that are able to efficiently and selectively convert CO2 into valuable products. Here, we provide an overview of recently obtained insights on electrolyte effects and we discuss how these insights can be used as design parameters for the construction of new electrocatalytic systems.

Low-Temperature Fast Production of Carbon and Acetic Acid Dual-Promoted Pd/C Catalysts

The Pd/C catalysts are widely used in synthesis of fine chemicals in industry, but their production suffers from a complicated two-step process involving impregnation and reduction, and requires large amounts of solvents and reductant, which would lead to a series of issues such as time consumption, resource waste and environmental pollution. Herein, ultra-small Pd nanoparticles uniformly anchored on carbon nanotubes (Pd/CNTs) were synthesized by using a one-pot and low-temperature reduction strategy. The present process/technology is very sensitive to and controlled by the supports and solvents, and the carbon support and acetic acid synergistically play crucial and decisive roles in the fast production of Pd/C catalysts. Also, the used solvents can be recycled and reutilized, which meets the requirements of sustainable chemistry and green economy. When the as-obtained Pd/CNTs catalyst was used to catalyze the oxidation of benzyl alcohol to benzaldehyde, it achieved a conversion efficiency as high as 99.3 % and a high selectivity up to >99.9 %. The simple, scalable and environmentally friendly strategy can be extended to anchor Pd nanoparticles on various carbon substrates, which sheds a new light on the synthesis of Pd/C catalysts.

Ensemble Effect in Bimetallic Electrocatalysts for CO2 Reduction

Alloying is an important strategy for the design of catalytic materials beyond pure metals. The conventional alloy catalysts however lack precise control over the local atomic structures of active sites. Here we report on an investigation of the active-site ensemble effect in bimetallic Pd-Au electrocatalysts for CO₂ reduction. A series of Pd@Au electrocatalysts are synthesized by decorating Au nanoparticles with Pd of controlled doses, giving rise to bimetallic surfaces containing Pd ensembles of various sizes. Their catalytic activity for electroreduction of CO₂ to CO exhibits a nonlinear behavior in dependence of the Pd content, which is attributed to the variation of Pd ensemble size and the corresponding tuning of adsorption properties. Density functional theory calculations reveal that the Pd@Au electrocatalysts with atomically dispersed Pd sites possess lower energy barriers for activation of CO₂ than pure Au and are also less poisoned by strongly binding *CO intermediates than pure Pd, with an intermediate ensemble size of active sites, such as Pd dimers, giving rise to the balance between these two rate-limiting factors and achieving the highest activity for CO₂ reduction.

Power to methanol technologies via CO2 recovery: CO2 hydrogenation and electrocatalytic routes

Various strategies are proposed to date in order to convert CO2 to large diversity of useful chemicals. The following review discusses two important approaches that produce methanol from CO2. These two includes CO2 hydrogenation and electrocatalytic routes. These processes could recycle CO2, permitting a carbon neutral, closed loop of fuel combustion and CO2 reduction to prevent a rising concentration of this greenhouse gas in the atmosphere. Besides, intermittent electricity generation can be stored in an energy-dense, portable form in chemical bonds. The present review reports more recent findings and drawbacks of these two processes. The present review study revealed that the hydrogenation process could become readily operational in comparison to electrocatalytic process. The electrocatalytic approach still has serious technical issues in terms of kinetically sluggish multi-electron transfer process during CO2 reduction reaction that requires excessive over-potential, relatively poor selectivity, poor durability in the long term, and the absence of the optimized standard experimental and commercial systems.

Cyclic two-step electrolysis for stable electrochemical conversion of carbon dioxide to formate

Pd metal and Pd-based alloys are ideal catalysts that allow for the electrochemical conversion of CO₂ to HCOO⁻ at almost zero-overpotential with high selectivity, but catalyst degradation caused by concurrent CO poisoning limits their practical implementation. Here, we demonstrate that cyclic two-step electrolysis, by applying the reduction and oxidation potentials alternately, achieves 100% current density stability and 97.8% selectivity toward HCOO⁻ production for at least 45 h. The key idea for achieving the reliability is based on the selective removal of CO by controlling the parameters during the oxidation step, which utilizes the different reversibility of HCOO⁻ and CO production reactions. Furthermore, it is found that potentiostatic electrolysis causes CO adsorption and subsequent dehydridation, which in turn lowers HCOO⁻ selectivity. Our work provides a system-level strategy for solving the poisoning issue that is inevitable in many electrocatalytic reactions.

Reduction of carbon dioxide is promising for the production of value-added chemicals, but electrocatalysts are hindered by carbon monoxide poisoning. Here, the authors alternate reduction and oxidation potentials to achieve stable and selective long-term electrocatalytic reduction of carbon dioxide to formate.

Alloy Nanocatalysts for the Electrochemical Oxygen Reduction (ORR) and the Direct Electrochemical Carbon Dioxide Reduction Reaction (CO2 RR)

In the face of the global energy challenge and progressing global climate change, renewable energy systems and components, such as fuel cells and electrolyzers, which close the energetic oxygen and carbon cycles, have become a technology development priority. The electrochemical oxygen reduction reaction (ORR) and the direct electrochemical carbon dioxide reduction reaction (CO₂ RR) are important electrocatalytic processes that proceed at gas diffusion electrodes of hydrogen fuel cells and CO₂ electrolyzers, respectively. However, their low catalytic activity (voltage efficiency), limited long-term stability, and moderate product selectivity (related to their Faradaic efficiency) have remained challenges. To address these, suitable catalysts are required. This review addresses the current state of research on Pt-based and Cu-based nanoalloy electrocatalysts for ORR and CO₂ RR, respectively, and critically compares and contrasts key performance parameters such as activity, selectivity, and durability. In particular, Pt nanoparticles alloyed with transition metals, post-transition metals and lanthanides, are discussed, as well as the material characterization and their performance for the ORR. Then, bimetallic Cu nanoalloy catalysts are reviewed and organized according to their main reaction product generated by the second metal. This review concludes with a perspective on nanoalloy catalysts for the ORR and the CO₂ RR, and proposes future research directions.

Cyanogel auto-reduction induced synthesis of PdCo nanocubes on carbon nanobowls: a highly active electrocatalyst for ethanol electrooxidation

Direct ethanol fuel cells (DEFCs) with a high conversion efficiency are quite promising candidates for energy conversion devices. Herein, we have successfully synthesized PdCo alloy nanocubes supported on carbon nanobowl (denoted as Pd₂Co₁/CNB) nanohybrids by using the cyanogel auto-reduction method at high temperature. The morphology, composition and structure of Pd₂Co₁/CNB nanohybrids are characterized in detail, revealing that PdCo nanocubes have a high alloying degree and special {110} facets. In cyclic voltammetry measurements, Pd₂Co₁/CNB nanohybrids show a mass activity of 1089.0 A g _Pd^-1 and a specific activity of 40.03 mA cm^-2 for ethanol electrooxidation at peak potential, which are much higher than that of the commercial Pd/C electrocatalyst (278.2 A g_Pd^-1 and 8.22 mA cm^-2). Additionally, chronoamperometry measurements show that Pd₂Co₁/CNB nanohybrids have excellent durability for ethanol electrooxidation. A high alloying degree, special {110} facets and the CNB supporting material contribute to the high activity and durability of Pd₂Co₁/CNB nanohybrids, making them a highly promising Pt-alternative electrocatalyst for ethanol electrooxidation in DEFCs.

Patterning Cu nanostructures tailored for CO2 reduction to electrooxidizable fuels and oxygen reduction in alkaline media

Due to the limited availability of noble metal catalysts, such as platinum, palladium, or gold, their substitution by more abundant elements is highly advisable. Considerably challenging is the controlled and reproducible synthesis of stable non-noble metallic nanostructures with accessible active sites. Here, we report a method of preparation of bare (ligand-free) Cu nanostructures from polycrystalline metal in a controlled manner. This procedure relies on heterogeneous localized electrorefining of polycrystalline Cu on indium tin oxide (ITO) and glassy carbon as model supports using scanning electrochemical microscopy (SECM). The morphology of nanostructures and thus their catalytic properties are tunable by adjusting the electrorefining parameters, i.e., the electrodeposition voltage, the translation rate of the metal source and the composition of the supporting electrolyte. The activity of the obtained materials towards the carbon dioxide reduction reaction (CO2RR), oxygen reduction reaction (ORR) in alkaline media and hydrogen evolution reaction (HER), is studied by feedback mode SECM. Spiky Cu nanostructures obtained at a high concentration of chloride ions exhibit enhanced electrocatalytic activity. Nanostructures deposited under high cathodic overpotentials possess a high surface-to-volume ratio with a large number of catalytic sites active towards the reversible CO2RR and ORR. The CO2RR yields easily electrooxidizable compounds - formic acid and carbon monoxide. The HER seems to occur efficiently at the crystallographic facets of Cu nanostructures electrodeposited under mild polarization.

Cu nanowire-catalyzed electrochemical reduction of CO or CO2

We prepared micrometer long Cu nanowires (NWs) of 25 and 50 nm diameters and studied their electrocatalysis for electrochemical reduction of CO/CO₂ in 0.1 M KHCO₃ at room temperature. The 50 nm NWs showed better selectivity than the 25 nm NWs, and catalyzed CO reduction to C₂-hydrocarbons (C₂H₄ + C₂H₆) with a combined faradaic efficiency (FE) of 60% (C₂H₄ FE of 35% and mass activity of 4.25 A g^-1 Cu) at -1.1 V (vs. reversible hydrogen electrode). The NW-catalyzed CO₂ reduction is less efficient due to the extra CO₂ to CO step required for the formation of C₂-hydrocarbons. This experimental evidence combined with DFT calculations suggests that CO is an important intermediate and NWs provide a large Cu(100) surface for *CO hydrogenation (to *CHO) and *CO-*CHO coupling, leading to more selective reduction of CO than CO₂ towards C₂-hydrocarbons.

Electrical energy storage with engineered biological systems

The availability of renewable energy technologies is increasing dramatically across the globe thanks to their growing maturity. However, large scale electrical energy storage and retrieval will almost certainly be a required in order to raise the penetration of renewable sources into the grid. No present energy storage technology has the perfect combination of high power and energy density, low financial and environmental cost, lack of site restrictions, long cycle and calendar lifespan, easy materials availability, and fast response time. Engineered electroactive microbes could address many of the limitations of current energy storage technologies by enabling rewired carbon fixation, a process that spatially separates reactions that are normally carried out together in a photosynthetic cell and replaces the least efficient with non-biological equivalents. If successful, this could allow storage of renewable electricity through electrochemical or enzymatic fixation of carbon dioxide and subsequent storage as carbon-based energy storage molecules including hydrocarbons and non-volatile polymers at high efficiency. In this article we compile performance data on biological and non-biological component choices for rewired carbon fixation systems and identify pressing research and engineering challenges.

Enhanced Bio-Electrochemical Reduction of Carbon Dioxide by Using Neutral Red as a Redox Mediator

Microbial electrosynthetic cells containing Methylobacterium extorquens were studied for the reduction of CO2 to formate by direct electron injection and redox mediator-assisted approaches, with CO2 as the sole carbon source. The formation of a biofilm on a carbon felt (CF) electrode was achieved while applying a constant potential of -0.75 V versus Ag/AgCl under CO2 -saturated conditions. During the biofilm growth period, continuous H2 evolution was observed. The long-term performance for CO2 reduction of the biofilm with and without neutral red as a redox mediator was studied by an applied potential of -0.75 V versus Ag/AgCl. The neutral red was introduced into the systems in two different ways: homogeneous (dissolved in solution) and heterogeneous (electropolymerized onto the working electrode). The heterogeneous approach was investigated in the microbial system, for the first time, where the CF working electrode was coated with poly(neutral red) by the oxidative electropolymerization thereof. The formation of poly(neutral red) was characterized by spectroscopic techniques. During long-term electrolysis up to 17 weeks, the formation of formate was observed continuously with an average Faradaic efficiency of 4 %. With the contribution of neutral red, higher formate accumulation was observed. Moreover, the microbial electrosynthetic cell was characterized by means of electrochemical impedance spectroscopy to obtain more information on the CO2 reduction mechanism.

Promoter Effects of Functional Groups of Hydroxide-Conductive Membranes on Advanced CO2 Electroreduction to Formate

The electrochemical reduction of CO₂ at ambient conditions provides a latent solution of turning waste greenhouse gases into commodity chemicals or fuels; however, a satisfactory ion-conducting membrane for maximizing the performance of a CO₂ electrolyzer has not been developed. Here, we report the synthesis of a sequence of hydroxide-conductive polymer membranes, which are based on polymer composites of poly(vinyl alcohol)/Guar hydroxypropyltrimonium chloride, for use in CO₂ electrolysis. The effect of different membrane functional groups, including thiophene, hydroxybenzyl, and dimethyloctanal, on the efficiency and selectivity of CO₂ electroreduction to formate is thoroughly evaluated. The membrane incorporating thiophene groups exhibits the highest Faradaic efficiency of 71.5% at an applied potential of -1.64 V versus saturated calomel electrode (SCE) for formate. In comparison, membranes containing hydroxybenzyl and dimethyloctanal groups produced lower efficiencies of 67.6 and 68.6%, respectively, whereas the commercial Nafion 212 membrane was only 57.6% efficient. The improved efficiency and selectivity of membranes containing thiophene groups are attributed to a significantly increased hydroxide conductivity (0.105 S cm^-1), excellent physicochemical properties, and the simultaneous attenuation of formate product crossover.

Theoretical insight into the electrocatalytic reduction of CO2 with different metal ratios and reaction mechanisms on palladium-copper alloys

Environmental impacts of continued CO2 production have led to an increased need for new methods of CO2 removal and energy development. Electrochemical reduction of CO2 has been shown to be a good method through recent studies. Alloys are of special interest for these applications, because of their unique chemical and physical properties that allow for highly active surfaces. Here, PdnCum (m + n = 15 and n > m) bimetallic electrocatalysts were used for systematic studies to understand the effect of the composition of Pd and Cu on the electrochemical reduction of CO2 to CO. In particular, the Pd-Cu alloy with the Pd/Cu = 2/1 atomic ratio (i.e., Pd10Cu5) has the best catalytic effect, particularly true at the step of the hydrogenation of CO2 to COOH, and the Pd10Cu5 catalyst is better than most known electrodes. With the energetic analysis of the proposed reaction pathways over the Pd10Cu5 catalyst, the limiting voltages for CO2 reduction to CH3OH, CH4, and CH3CH2O have been compared. Most importantly, the kinetic model analysis showed that the rate constant values indicate that the probability of generating C2H5OH on the Pd10Cu5 catalyst is greater than that of CH3OH or CH4. The findings revealed in this study may shed some light on the design of cost-effective and efficient electrocatalysts for CO2 conversion to CO or to other useful hydrocarbons.

Pd-Co nanoalloys nested on CuO nanosheets for efficient electrocatalytic N2 reduction and room-temperature Suzuki-Miyaura coupling reaction

Due to their synergistic and tunable effects, bimetallic alloy systems have recently attracted considerable attention as superior catalysts. Herein, Pd-Co bimetallic alloy nanoparticles were uniformly deposited onto CuO nanosheet supports. This nanostructured catalyst was first shown to be an effective catalyst to convert N2 to NH3 in 0.1 M KOH with a yield of 10.04 μg h-1 mg-1cat. and a faradaic efficiency of 2.16%. The catalyst also performed well in the Suzuki-Miyaura coupling reaction at room temperature without an inert atmosphere and any toxic solvents. Thus, the catalyst is consistent with the principles of green chemistry. Due to the synergistic effects, this bimetallic Pd-Co catalyst shows higher catalytic activity than its monometallic counterparts. Moreover, the Pd/Co ratio was tuned to achieve the best catalytic performance. Finally, the Pd-Co/CuO catalyst presented good stability and recyclability. The superior catalytic activity of the bimetallic alloy catalyst make it an alternative material for catalytic applications in the future.

Efficient reduction of formic acid to formaldehyde by zinc

The possibility of thermally reducing formic acid to formaldehyde selectively has been probed using metallic zinc. Good selectivity (over 80%) was obtained with low concentrations of formic acid, with methanol and methyl formate as secondary products. The selectivity can be tuned by changing the carrier gas flow, temperature, and zinc amount. Zinc was oxidized to zinc oxide during this process.

Mechanistic insights into C2 and C3 product generation using Ni3Al and Ni3Ga electrocatalysts for CO2 reduction

Thin films of Ni3Al and Ni3Ga on carbon solid supports have been shown to generate multi-carbon products in electrochemical CO2 reduction, an activity profile that, until recently, was ascribed exclusively to Cu-based catalysts. This catalytic behavior has introduced questions regarding the role of each metal, as well as other system components, during CO2 reduction. Here, the significance of electrode structure and solid support choice in determining higher- versus lower-order reduction products is explored, and the commonly invoked Fischer-Tropsch-type mechanism of CO2 reduction to multi-carbon products is indirectly probed. Electrochemical studies of both intermetallic and non-mixed Ni-Group 13 catalyst films suggest that intermetallic character is required to achieve C2 and C3 products irrespective of carbon support choice, negating the possibility of separate metal sites performing distinct yet complementary roles in CO2 reduction. Furthermore, Ni3Al and Ni3Ga were shown to be incapable of generating higher-order reduction products in D2O, suggesting a departure from accepted mechanisms for CO2 reduction on Cu. Additional routes to multi-carbon products may therefore be accessible when developing intermetallic catalysts for CO2 electroreduction.

Electrocatalytic conversion of carbon dioxide to formic acid over nanosized Cu6Sn5 intermetallic compounds with a SnO2 shell layer

FE towards formation of formic acid over Cu₆Sn₅ core–Sn oxide shell structure was higher than that of Sn plate and Sn NP/CB. We believe that the key factor affecting the high selectivity is a compressive strain of surface.

Surface strategies for catalytic CO2 reduction: from two-dimensional materials to nanoclusters to single atoms

This work constructively reviewed and predicted the surface strategies for catalytic CO₂ reduction with 2D material, nanocluster and single-atom catalysts

Bifunctional electrocatalysis for CO2 reduction via surface capping-dependent metal–oxide interactions

Cetyltrimethylammonium bromide capping on Au renders desirable chemical interactions with SnO₂, enabling selective bifunctional CO₂ electroreduction.

A Molecular CO2 Reduction Catalyst Based on Giant Polyoxometalate {Mo368}

Photocatalytic CO2 reduction in water is one of the most attractive research pursuits of our time. In this article we report a giant polyoxometalate {Mo368} based homogeneous catalytic system, which efficiently reduces CO2 to formic acid with a maximum turnover number (TON) of 27,666, turnover frequency (TOF) of 4,611 h-1 and external quantum efficiency of the reaction is 0.6%. The catalytic system oxidizes water and releases electrons, and these electrons are further utilized for the reduction of CO2 to formic acid. A maximum of 8.3 mmol of formic acid was observed with the loading of 0.3 μmol of the catalyst. Our catalyst material is also stable throughout the reaction. The starting materials for this experiment are CO2 and H2O and the end products are HCOOH and O2. The formic acid formed in this reaction is an important H2 gas carrier and thus significant in renewable energy research.

Bimetallic Electrocatalysts for CO2 Reduction

The increasing concentration of CO₂ in the atmosphere has caused various environmental issues. Utilizing CO₂ as the carbon feedstock to replace traditional fossil sources in commodity chemical production is a potential solution to reduce CO₂ emissions. Electrochemical reduction of CO₂ has attracted much attention because it not only converts CO₂ into a variety of useful chemicals under mild reaction conditions, but also can be powered by renewable electricity at remote locations. From this review article, we summarize recent literature on the topic of bimetallic electrocatalysts for CO₂ reduction. Both selectivity and activity of bimetallic catalysts strongly depend on their compositions and surface structures. Tuning the properties of a bimetallic catalyst could result in a wide range of products, including carbon monoxide, hydrocarbons, carboxylate and liquid oxygenates. By reviewing recent research efforts in the field of bimetallic electrocatalysts for CO₂ reduction, we aim to provide the community with a timely overview of the current status of bimetallic CO₂ electrocatalysts and to stimulate new ideas to design better catalysts for more efficient CO₂ electrolysis processes.

2D Metal Oxyhalide-Derived Catalysts for Efficient CO2 Electroreduction

Electrochemical reduction of CO₂ is a compelling route to store renewable electricity in the form of carbon-based fuels. Efficient electrochemical reduction of CO₂ requires catalysts that combine high activity, high selectivity, and low overpotential. Extensive surface reconstruction of metal catalysts under high productivity operating conditions (high current densities, reducing potentials, and variable pH) renders the realization of tailored catalysts that maximize the exposure of the most favorable facets, the number of active sites, and the oxidation state all the more challenging. Earth-abundant transition metals such as tin, bismuth, and lead have been proven stable and product-specific, but exhibit limited partial current densities. Here, a strategy that employs bismuth oxyhalides as a template from which 2D bismuth-based catalysts are derived is reported. The BiOBr-templated catalyst exhibits a preferential exposure of highly active Bi ( 11¯0 ) facets. Thereby, the CO₂ reduction reaction selectivity is increased to over 90% Faradaic efficiency and simultaneously stable current densities of up to 200 mA cm^-2 are achieved-more than a twofold increase in the production of the energy-storage liquid formic acid compared to previous best Bi catalysts.