Electrochemical Fragmentation of CuO Nanoparticles Enhancing Selective C-C Coupling from CO Reduction Reaction.

In this study, we demonstrate that the initial morphology of nanoparticles can be transformed into small fragmented nanoparticles, which were densely contacted to each other, during electrochemical CO reduction reaction (CORR). Cu-based nanoparticles were directly grown on a carbon support by using cysteamine immobilization agent, and the synthesized nanoparticle catalyst showed increasing activity during initial CORR, doubling Faradaic efficiency of CH production from 27% to 57.3%. The increased CH production activity was related to the morphological transformation over reaction time. Twenty nm cubic CuO crystalline particles gradually experienced in situ electrochemical fragmentation into 2-4 nm small particles under the negative potential, and the fragmentation was found to be initiated from the surface of the nanocrystal. Compared to Cu@CuO nanoparticle/C or bulk Cu foil, the fragmented Cu-based NP/C catalyst achieved enhanced C production selectivity, accounting 87% of the total CORR products, and suppressed H production. In-situ X-ray absorption near edge structure studies showed metallic Cu state was observed under CORR, but the fragmented nanoparticles were more readily reoxidized at open circuit potential inside of the electrolyte, allowing labile Cu states. The unique morphology, small nanoparticles stacked upon on another, is proposed to promote C-C coupling reaction selectivity from CORR by suppressing HER.