MoP4/Ni3S2/MoO3 heterogeneous structure nanorod arrays for efficient solar-enhanced overall water splitting

Abstract

NiMo-based materials are promising candidates for alkaline overall water splitting. Unfortunately, the catalytic activity of most nickel–molybdenum based electrocatalysts is still far below the standard for practical applications. Therefore, the development of new nickel–molybdenum-based multi-component catalysts is expected to achieve complementary advantages and improve electrocatalytic water splitting activity. Herein, we have synthesized a multi-phase heterostructured electrocatalyst grown on NiMoO₄ nanorods using the strategy of simultaneous phosphatization and sulfidation. The interface formed between multi-phase heterostructures plays a crucial role in solar-enhanced overall water splitting. According to the experimental results, at a current density of 10 mA cm⁻², the required overpotentials of MoP₄/Ni₃S₂/MoO₃/α-NiMoO₄/β-NiMoO₄ (NiMo-PS@NF) catalysts for the HER and OER are as low as 35 mV and 211.8 mV, respectively. The overall water splitting cell voltage is as low as 1.391 V (10 mA cm⁻²) due to the high intrinsic activity and efficient electron transfer efficiency. Meanwhile, the bifunctional electrocatalyst can operate continuously for at least 65 hours at 100 mA cm⁻² current density. Notably, this electrocatalyst exhibits enhanced electrocatalytic water splitting activity under simulated sunlight irradiation. Surprisingly, the electrocatalyst exhibits a solar-to-hydrogen efficiency of 19.42% in a photoelectric coupled water splitting system. In addition, the density functional theory (DFT) results are in agreement with the experimental results. This work provides a new idea for improving electrocatalytic activity by rational use of solar energy.