Heterostructure CoP2-Fe2P//CoWO4 as a pH-universal and multifunctional catalyst for efficient hydrogen evolution and ethanol oxidation.

Developing highly efficient and economical electrocatalysts with both high activity and excellent stability for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and ethanol oxidation reaction (EOR) remains a significant challenge. In our work, a heterostructure CoP2-Fe2P//CoWO4 catalyst has been successfully integrated onto Ni foam via a two-step hydrothermal reaction and a phosphorization process. Electrochemical evaluations confirm a synergistic catalytic effect between CoP2 and Fe2P. The CoP2-Fe2P//CoWO4 catalyst exhibits enhanced HER catalytic activity across a wide pH range, requiring relatively low overpotentials of only 42, 138 and 32 mV to achieve 10 mA cm-2 under alkaline, neutral and acidic conditions, respectively. Meanwhile, for the EOR, the CoP2-Fe2P//CoWO4 catalyst requires a potential of only 1.37 V to achieve 100 mA cm-2, which is much lower than that required for the OER (1.53 V). Furthermore, density functional theory (DFT) calculations and Raman spectroscopy reveal that high-valence metal species CoOOH and FeOOH are likely the real active species responsible for water dissociation and EOR, respectively. This work may provide a new pathway for heterostructured catalysts based on transition metal phosphides in the field of small-molecule electrolysis.