Uniform nodule-like Ni3C/Ni heterostructure templated by metal–organic frameworks for high-performance overall water splitting†

Developing highly active and low-cost electrocatalysts for efficient water electrolysis is of great significance for energy and environment sustainability. In this work, a highly efficient, durable and stable bi-functional electrocatalyst nickel carbide/nickel heterojunction on Ni foam (NF) (Ni₃C/Ni@NF) with an interconnected nano-sized nodule architecture was facilely synthesized via an in situ nickel metal–organic framework (Ni-MOF) pyrolysis process at relatively low temperature. The optimized Ni₃C/Ni@NF electrode exhibits outstanding catalytic performance with extremely low overpotentials of only 16 and 268 mV at current densities of 10 mA cm⁻² for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Furthermore, it exhibits overpotential as low as 1.55 V (η₁₀) for overall water splitting. The experimental studies and density functional theory (DFT) calculations clarified that the optimized synergistic effect of the Ni₃C/Ni heterojunction triggers the enlarged active surface area and rapid charge transfer, thus enhancing the intrinsic catalytic activity. This work paves a convenient pathway for the rational construction of robust Ni-based heterojunction electrocatalysts with high activity for hydrogen/oxygen production and energy conversion in practical applications.