Construction of superhydrophilic FeP–Ni2P–CoP/NF enriched interfacial heterostructures for promoting efficient and stable overall water splitting under large currents†

Abstract

It is of great importance to devise highly effective and durable non-precious metal catalysts capable of operating at high current densities, in order to cater to the requirements of practical applications. Here, FeP–Ni₂P–CoP heterostructured catalysts grown on NF (Ni foam) were prepared by a simple one-step hydrothermal and low-temperature phosphatization strategy. The optimized FeP–Ni₂P–CoP/NF catalysts exhibited excellent catalytic activity in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The HER and OER overpotentials are 128 mV and 256 mV at 100 mA cm⁻², and high current densities of 500 mA cm⁻² can be achieved with only 190 mV and 288 mV. Impressively, the electrolyzer requires only an ultra-low cell voltage of 1.5 V to reach 10 mA cm⁻². In addition, the catalyst was able to operate stably at a high current density of 1000 mA cm⁻² for 500 hours. This is mainly attributed to the heterogeneous structure of FeP–Ni₂P–CoP/NF nanowires, which exposes more active area, accelerates ionic transport and bubble release, and alters the local electronic structure of the interface, thereby improving its hydrophilicity and enhancing the intrinsic activity and stability. This work provides new ideas for the use of polymetallic-based phosphides for overall water decomposition at high current densities.