Carbon Monoxide Reduction Reaction to Produce Multicarbon Products in Acidic Electrolytes Using Gas Diffusion Electrode Loaded with Copper Nanoparticles

Kurihara R., Nagita K., Ohashi K., et al. Carbon Monoxide Reduction Reaction to Produce Multicarbon Products in Acidic Electrolytes Using Gas Diffusion Electrode Loaded with Copper Nanoparticles. Advanced Materials Interfaces , (2023); https://doi.org/10.1002/admi.202300731.The synthesis of multi-carbon products (C2+) by electrochemical CO2 reduction reaction (CO2RR) is a promising technology that will contribute to the realization of a carbon-neutral society. In particular, efficient CO2RR to produce C2+ in acidic electrolytes is desirable because the conversion of CO2 to inert (bi)carbonate can be suppressed under acidic conditions, thereby increasing the efficiency of substrate CO2 utilization. Herein, since C2+ products are produced via the dimerization of carbon monoxide, an intermediate in CO2RR, the focus is on the carbon monoxide reduction reaction (CORR). A gas diffusion electrode loaded with copper nanoparticles is used in acidic electrolytes to investigate the conditions necessary for efficient C2+ production. The faradaic efficiency and partial current density for C2+ production attained 75% and 280 mA cm−2 in a pH 2.0 solution, and they reached up to 66% and 260 mA cm−2 even in a pH 1.0 solution. Numerical simulations showed that increasing the alkalinity of the electrode surface to greater than pH 7 by consuming protons is necessary to facilitate the production of C2+ during the CORR. When the desired level of alkalinity is achieved, the concentration and type of alkali cations present at the electrode surface have an impact on the selectivity for C2+ production

C−C Coupling in CO2 Electroreduction on Single Cu‐Modified Covalent Triazine Frameworks: A Static and Dynamic Density Functional Theory Study

Abstract The electrochemical reduction of CO2 into C2+ products represents a promising solution to completing the carbon cycle, thereby fostering a sustainable energy supply. Single‐atom electrocatalysts (SAECs) have garnered significant attention as efficient electrocatalysts for the CO2 reduction reaction. Herein, we carried out a first‐principles study on the mechanism of C−C bond formation on single‐Cu‐atom‐modified covalent triazine frameworks (Cu‐CTFs), which are a promising platform for SAECs. Static density functional calculations indicated that the dimerization of CO, which is the main mechanism for C−C bond formation on bulk Cu metals, was not favorable for Cu‐CTFs because of the lack of adjacent Cu sites for co‐adsorption of CO molecules. Rather than CO dimerization, the reaction between adsorbed *CHO and CO to produce *COCHO has a relatively low reaction energy barrier. Constrained ab initio molecular dynamics analyses revealed that the C−C bond‐forming reaction proceeds via insertion of CO at the *CHO intermediate, which has a modest activation energy of 0.09 eV. Specifically, when CO molecule is constrained to be brought close to *CHO, CO insertion between *CHO and Cu occurs at a C−C distance of 1.8 Å. This insertion reaction is the transition step for this C−C bond formation

Carbon Monoxide Reduction Reaction to Produce Multicarbon Products in Acidic Electrolytes Using Gas Diffusion Electrode Loaded with Copper Nanoparticles

Abstract The synthesis of multi‐carbon products (C2+) by electrochemical CO2 reduction reaction (CO2RR) is a promising technology that will contribute to the realization of a carbon‐neutral society. In particular, efficient CO2RR to produce C2+ in acidic electrolytes is desirable because the conversion of CO2 to inert (bi)carbonate can be suppressed under acidic conditions, thereby increasing the efficiency of substrate CO2 utilization. Herein, since C2+ products are produced via the dimerization of carbon monoxide, an intermediate in CO2RR, the focus is on the carbon monoxide reduction reaction (CORR). A gas diffusion electrode loaded with copper nanoparticles is used in acidic electrolytes to investigate the conditions necessary for efficient C2+ production. The faradaic efficiency and partial current density for C2+ production attained 75% and 280 mA cm−2 in a pH 2.0 solution, and they reached up to 66% and 260 mA cm−2 even in a pH 1.0 solution. Numerical simulations showed that increasing the alkalinity of the electrode surface to greater than pH 7 by consuming protons is necessary to facilitate the production of C2+ during the CORR. When the desired level of alkalinity is achieved, the concentration and type of alkali cations present at the electrode surface have an impact on the selectivity for C2+ production

CO Hydrogenation Promoted by Oxygen Atoms Adsorbed onto Cu(100)

The electrochemical CO2 reduction reaction (CO2RR) on Cu-based catalysts is a promising method for converting anthropogenic CO2 to valuable chemical feedstocks and fuels. Although pure CO2 gas has been widely used as a reactant in CO2RR-related research, CO2 gas collected from the atmosphere inevitably includes some amount of various impurity gases in the actual application of this method. Among such impurities, O2 gas has high reactivity and can easily contaminate the reaction environment, thereby substantially affecting the reactivity of the CO2RR. Herein, we performed first-principles calculations for the CO2RR in the presence of O2 reduction reaction intermediates on the Cu(100) surface. Specifically, we calculated the reaction and activation free energies for the hydrogenation of adsorbed CO* to CHO* on a Cu(100) surface covered with O* or OH*. When the coverage of O* reached 25%, the initial state of CO hydrogenation became destabilized to a greater extent than the transition state, which decreased the reaction and activation free energies by 0.27 and 0.16 eV, respectively. The projected density of states analyses revealed that O* weakens the interaction between CO* and the Cu surface, whereas OH* less strongly affects CO hydrogenation