Integrating the active OER and HER components as the heterostructures for the efficient overall water splitting

Developing the efficient and low-cost electrocatalysts for overall water splitting is of the great importance for the production of H₂. The popular bi-functional catalysts usually shown good activity for one half reaction at expense of the activity for another half-reaction, thus given a moderate performance for overall water splitting. In this paper, we have reported on integrating the active OER (Ni₃N) and HER (NiMoN) components as Ni₃N-NiMoN heterostructures for the effective overall water splitting. The heterostructures were constructed by the controllable nitridation of the Ni-Mo-O precursor anchored on carbon cloth (CC) under NH₃ atmosphere. The micro-structures of the catalyst could be tuned by regulating the surface properties of CC and the calcination temperature. Under optimized condition, the Ni₃N-NiMoN catalysts exhibited good catalytic activity for both OER and HER in alkaline electrolyte. The catalysts can achieve a current density of 10 mA cm⁻² at an overpotential of 31 mV for HER, being close to Pt catalyst. Also, it only requiring an overpotential of 277 mV to reach current density of 10 mA cm⁻² for OER. Moreover, the cell assembled by the identical Ni₃N-NiMoN as both the cathode and anode needs only a cell voltage of 1.54 V to achieve current density of 10 mA cm⁻². The superior performance of Ni₃N-NiMoN heterostructures can be ascribed to the following points: 1) the simultaneous presence of active OER and HER components and the promoted action each other in the heterostructures, and 2) the exposure of the abundant active sites in the sheet-like structure assembled by the nanoparticles.