Oxygen Vacancy and Heterostructure Modulation of Co₂P/Fe₂P Electrocatalysts for Improving Total Water Splitting

Designing a stable and highly active catalyst for hydrogen evolution and oxygen evolution reactions (HER/OER) is essential for the industrialization of hydrogen energy but remains a major challenge. This work reports a simple approach to fabricating coupled Co₂P/Fe₂P nanorod array catalyst for overall water decomposition, demonstrating the source of excellent activity in the catalytic process. Under alkaline conditions, Co₂P/Fe₂P heterostructures exhibit an overpotential of 96 and 220 mV for HER and OER, respectively, at 10 mA cm^-2. For total water splitting, a low voltage of 1.56 V is required to provide a current density of 10 mA cm^-2. And the catalyst exhibits long-term durability for 30 h at a high current density of 250 mA cm^-2. The analysis of the results revealed that the presence of interfacial oxygen vacancies and the strong interaction between Co₂P/Fe₂P provided the catalyst with more electrochemically active sites and a faster charge transfer capability, which improved the hydrolysis dissociation process. Electrochemically active metal (oxygen) hydroxide phases were produced after OER stability testing. The results of this study prove its great potential in practical industrial electrolysis and provide a reasonable and feasible strategy for the design of nonprecious metal phosphide electrocatalysts.