High-entropy CoNiFeCuP nanoparticles as efficient and durable catalysts for alkaline oxygen evolution reaction

Abstract

Designing high-performance oxygen evolution reaction (OER) catalysts is crucial for improving water electrolysis efficiency. High-entropy phosphides (HEPs) have gained attention owing to their abilities to modulate their electronic structures via P atoms and exhibit high durability due to the high-entropy effect. However, the understanding of the relationship between metal (M)–M and M–P interactions and catalytic activity remains limited, and synthesis of HEPs is still complex. Accordingly, herein, we developed a facile colloidal method for the production of HEPs and compared various elemental combinations, that is, CoNiP, CoNiCuP, CoNiFeP, and CoNiFeCuP. As entropy increased, changes in the oxidation states of M and P became more pronounced, correlating with the OER activity. The CoNiFeCuP catalyst demonstrated an excellent OER activity (exhibiting a low overpotential of 244 mV at 10 mA cm⁻²) because of multimetal interactions, and the activity of the catalysts was in the following order: CoNiFeCuP > CoNiFeP > CoNiCuP > CoNiP. Strong M–P bonds in HEPs, along with entropy stabilization and the hollow structure, enhanced the catalytic activity, suppressed metal leaching, and ensured catalytic durability for over 100 h. In situ Raman spectroscopy revealed the surface reorganization of CoNiFeCuP NPs into Co/NiOOH during the OER, which accelerated the reaction. Overall, the simple synthesis of HEPs and understanding of the M–M and M–P interactions highlight the potential of HEPs as efficient and durable OER catalysts.