Tuning work function difference of copper/cobalt oxides heterointerfaces enables efficient electrochemical nitrate reduction

Metal/metal-oxide heterointerfaces receive extensive attention in electrocatalysis on account of the strong synergy between the two components at the interface. However, the key factor governing such interfacial synergy is still unclear, making it extremely challenging to rationally design electrocatalyst with desired heterointerfaces. Here, we select metallic copper/cobalt-oxide (i.e., Cu/Co3O4) heterointerfaces as model catalysts for the nitrate reduction reaction (NO3-RR) and tuned work function difference (AO) between Cu/Co3O4 by introducing oxygen vacancies (Ov) on Co3O4. By combing experimental and theoretic results, we observe that the AO is a key factor that governs the interfacial synergy, which included the transfer of electrons from Cu to Co3O4 and the spillover of hydrogen from Co3O4 to Cu. Consequently, the Cu/Co3O4 interface with an optimized AO displayed the best NO3  RR performance, outperforming most of other reported electrocatalysts. The above findings will create new opportunities for rationally designing heterointerfaces for efficient electrocatalysis by tuning AO.