A Fe–Ni5P4/Fe–Ni2P heterojunction electrocatalyst for highly efficient solar-to-hydrogen generation

Abstract

Hydrogen generation through solar-driven water splitting is a promising green technology for the sustainable development of human society; however, its wide application is severely restricted by the expensive noble-metal electrocatalysts. Herein, a novel Fe–Ni₅P₄/Fe–Ni₂P (H-FeNiP) heterojunction electrocatalyst is developed by simultaneously taking advantage of the heterojunction effect and the doping effect. It shows excellent activity for both the oxygen and hydrogen evolution reactions in alkaline solution, which only require overpotentials of 231 ± 3 mV and 86 ± 8 mV to deliver 10 mA cm⁻², respectively. Density functional theory (DFT) calculations reveal that the heterojunction structure can induce charge transfer from the underlying layer to the surface, which is effective in reducing the activation energy barrier for the HER and OER intermediates. This favorable activity enables the H-FeNiP couple to exhibit an impressive solar-to-hydrogen performance when connected with an organic solar cell (PTB7-Th/PC₇₁BM/CO_i8DFIC), the power conversion ratio of which (73.10%) is even higher than that of the commercial Pt‖RuO₂ couple (69.98%). Overall, this study conceptually provides an alternative avenue for cost-effective hydrogen generation in an environmentally friendly manner for the future.