(Invited) Electrochemical CO2 Reduction Reaction to C2 Chemicals with Cu-Based Nanocatalysts

Cu is an interesting electrocatalyst for CO 2 reduction reaction (CO 2 RR) due to its unique capability to produce various hydrocarbon chemical in addition to H 2 , and the nanostructures of Cu surface significantly affect the product selectivity for C 2+ over C1 chemicals. Although material engineering strategies have aimed at the design of a selective C2+-producing catalyst, the role of the fundamental descriptor allowing control of the desired pathway is not yet well-understood. In this context, reliable guidelines for highly selective reactions require understanding the catalyst material and characterization. Both of a H-cell and gas-diffusion-electrode (GDE) based gas-fed cells have shown the enhanced ethylene selectivity with Cu nanoparticles prepared by oxide forms. The fragmented Cu surfaces having high defects or grain boundaries are proposed as active sites for C-C coupling based on the material characterization. In addition, in-situ spectroscopy such as X-ray absorption spectroscopy, Raman spectroscopy, and infrared absorption spectroscopy can provide additional information of the catalyst and intermediate operando condition. We demonstrated that there are active sites that activate the dimerization of CO, and C-C coupling occurs exclusively by CO dimerization, without the participation of *CHO which is proposed as an intermediate for CH 4 production. We expect that these findings will aid the understanding of the CO 2 RR mechanism, and that the disclosed structures and kinetics of the surface intermediates will enable the design of improved catalysts for future CO 2 RR.