NiFeCoMoCr high-entropy hydroxides for efficient bifunctional alkaline water splitting and renewable hydrogen storage

High-entropy materials have gained significant attention in the field of electrocatalysis for water electrolysis due to their adaptable electronic properties and the synergistic effects arising from the presence of multiple components. In this context, high-entropy hydroxides (HEHs) have emerged as a focal point of research, attributed to their layered structures and the excellent oxygen evolution reaction (OER) catalytic activity. Herein, a NiFeCoMoCr-HEH catalyst featuring a nanocrystalline structure was synthesized by a one-step hydrothermal method, resulting in the formation of a three-dimensional hierarchical architecture characterized by grape-shaped microspheres comprising interconnected 2D nanosheets. The catalyst demonstrated remarkable OER performance in alkaline conditions, achieving a minimal overpotential of 271.81 mV for a current density of 100 mA cm −2 and maintaining stability for 55 h. To enhance the hydrogen evolution reaction (HER) activity of the catalyst, a minimal amount of Pt metal was deposited onto the NiFeCoMoCr-HEH surface. The Pt-NiFeCoMoCr-HEH catalyst achieved a HER overpotential of 31.85 mV at 10 mA cm −2 with 24 h durability. Upon integration into a water electrolyzer, the coupled Pt-NiFeCoMoCr-HEH||NiFeCoMoCr-HEH system delivered 50 mA cm −2 at 1.58 V, significantly lower than conventional Pt/C||IrO 2 /C systems (1.67 V). Impressively, the system was successfully powered by solar and wind energy, yielding hydrogen and showcasing its viability for renewable energy storage. This work highlights the promise of HEH-based catalysts in advancing environmentally friendly hydrogen production.