Heterogeneous Interface Engineering of CoMoP/C ₃ N ₄ /N‐Doped Carbon to Boost Overall Water Splitting

ABSTRACT The design of efficient and cost‐effective bifunctional catalysts, which are capable of driving both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is of paramount importance for advancing overall water splitting. Here, we developed an innovative heterogeneous interface engineering strategy to boost the electrocatalytic performance of overall water splitting. This approach involves the synergistic integration of ultra‐fine CoMoP nanocrystals coupled with three‐dimensional (3D) porous C 3 N 4 /N‐doped carbon (NC) architectures, constructing a distinctive CoMoP/C 3 N 4 /NC heterogeneous interface. The CoMoP/C 3 N 4 /NC exhibits distinguished overall water splitting performance. To drive the overall water splitting current of 10 mA cm −2 , the CoMoP/C 3 N 4 /NC||CoMoP/C 3 N 4 /NC electrolysis cell only needs an ultralow cell voltage of 1.496 V. The electronic properties and localized coordination environments characterizations, and density functional theory (DFT) calculations elucidate that the improved catalytic activities of CoMoP/C 3 N 4 /NC are primarily attributed to the synergistic interfacial coupling between CoMoP/C 3 N 4 /NC heterogeneous interface. A novel multi‐site synergistic catalytic mechanism was revealed by the DFT calculations, in which the optimum H* adsorption site on CoMoP/C 3 N 4 /NC for HER is on the cobalt atoms in CoMoP with the ultralow Gibbs free energy of hydrogen bonding (Δ G H* ) of 0.018 eV, while for the OER, the optimum intermediates adsorption site of the CoMoP/C 3 N 4 /NC is on the carbon atoms in C 3 N 4 /NC. Besides, the intricately engineered 3D hierarchical porous framework of the CoMoP/C 3 N 4 /NC can facilitate the ion and electron transport and improve mass transfer, which gives rise to enhanced water splitting performance.