In situ surface reconstruction of heterostructure Ni2P/CoP/FeP4 nanowires network catalyst for high-current-density overall water splitting

Abstract

Considering the imperative need for cost-effective electrocatalysts for water electrolysis, a novel Ni₂P/CoP/FeP₄/IF electrocatalyst nanowires network was synthesized in this study. Owing to the strong synergistic effects and high exposure of the active sites, Ni₂P/CoP/FeP₄/IF exhibited exceptional performance in both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), demonstrating low overpotentials of 218 and 127 mV at 100 mA cm^–2 in alkaline media, respectively. Furthermore, the water electrolyzer based on Ni₂P/CoP/FeP₄/IF bifunctional catalyst requires only 1.50 and 2.05 V to reach 10 and 500 mA cm^–2, respectively, indicating its potential for large-scale hydrogen production. Comprehensive ex situ characterizations and in situ Raman spectra reveal that Ni₂P/CoP/FeP₄/IF undergoes rapid reconstruction during the OER to form the corresponding (oxy) hydroxide species, which serve as the real active sites. Furthermore, density functional theory calculations clarified that during the HER process, H₂O is adsorbed at the Fe site of Ni₂P/CoP/FeP₄/IF for hydrolysis, with the resultant H* adsorbed at the Ni site for desorption. Introducing CoP promoted water adsorption and increased the HER activity of the catalyst. Hence, this study offers a pathway for designing highly efficient catalysts that leverage the interface effects.