Investigating the Effect of the Initial Valence States of Copper on CO2 Electroreduction

Abstract Abstract : The valence states of copper always play an important role for the most studied copper‐based catalysts in CO 2 electroreduction (CO 2 ERR). In this work, distinct Cu, Cu 2 O, and CuO nanoparticles with similar particle size on active carbon are synthesized via carbonthermal reduction. Although all CuO x nanoparticles are reduced to metallic Cu during CO 2 ERR, their different initial valence states result in particle‐size variations and different CO 2 ERR performances. Cu nanoparticles in Cu/C evolve into smaller particles, while those derived from Cu 2 O/C and CuO/C agglomerate into larger ones. The optimal CO production potential of CO drops with decreasing particle size and is as low as −0.7 V (vs. the eversible hydrogen electrode) on Cu/C. Furthermore, Cu nanoparticles in Cu/C expose much more active sites with higher electrochemical active area and stronger CO adsorption, which further promote C−C coupling to produce C 2+ products while inhibiting competitive hydrogen evolution.