Reconfiguration of a mixed-valence copper complex during CO electroreduction promotes CO-to-CH conversion.

Understanding the structural changes of high-performance CO-to-CH catalysts and determining the mode of C-C coupling at active sites during the electrochemical CO reduction reaction (ECORR) are crucial. Molecular catalysts with readily identifiable and uniform active sites permit the elucidation of reaction mechanisms at the molecular level, serving as an optimal platform for investigating the ECORR. Here we report the dynamic structural reconfiguration of a mixed-valence copper-based complex ([CuCl(phen)][CuCl]; phen = 1,10-phenanthroline) during the ECORR and elucidate the mechanism for its enhanced selectivity towards CH. The [CuCl(phen)][CuCl] catalyst exhibits outstanding performance with a maximum faradaic efficiency for CH of 47% at -1.2 V RHE. The excellent performance is maintained for at least 4.5 h. During the ECORR, the Cu(II) in the [CuCl(phen)] unit is reduced to Cu(I) and the chlorine atom dissociates at high potential to form an exposed Cu(I) site, possibly resulting in cuprophilic interactions between the two Cu sites. The reconstruction shortens the Cu-Cu distance in the [CuCl(phen)][CuCl] complex, facilitating the dimerization of *CO and *CHO intermediates to produce CH. This work presents a fresh perspective on designing ECORR catalysts to produce multi-carbon products through an reconfiguration process.