Extraordinary d–d hybridization in Co(Cu)0.5OxHy microcubes facilitates PhCH2O* –Co(Ⅳ) coupling for benzyl alcohol electrooxidation

A series of bimetallic hydroxides Co(M)0.5OxHy (M = Cu, Ni, Mn, Zn) were fabricated for the benzyl alcohol oxidation reaction (BAOR). The active origin and synergistic effect of bimetallic electrocatalysts were adequately deciphered. The reaction was found be principally initiated from the sequential oxidation of Co2+ (i.e., Co2+ to Co3+ to Co4+), followed by the spontaneous proton–coupled electron transfer (PCET) process between Co4+ and benzyl alcohol (BA) molecules. Besides, the adsorption free energy of BA molecules on Co(Cu)0.5OxHy was successfully optimized by Cu doping owing to the extraordinary d–d orbital hybridization between Co and Cu atom. As a result, an extra high conversion rate (95.3%) of BA and selectivity (98.2%) of benzoic acid were achieved under 0.5 V vs. Hg/HgO. These insights are essential for a comprehensive understanding of the BAOR mechanism and the design of Co–based catalysts.