Interface Engineering on Amorphous/Crystalline Hydroxides/Sulfides Heterostructure Nanoarrays for Enhanced Solar Water Splitting

Developing highly efficient and stable noble-metal-free electrocatalysts for water splitting is critical for producing clean and sustainable energy. Here, we design a hierarchical transition metal hydroxide/sulfide (NiFe(OH)_x-Ni₃S₂/NF) electrode with dual heterointerface coexistence using a cation exchange-induced surface reconfiguration strategy. The electrode exhibits superior electrocatalytic activities, achieving low overpotentials of 55 mV for hydrogen evolution and 182 mV for oxygen evolution at 10 mA cm^-2. Furthermore, the assembled two-electrode system requires voltages as low as 1.55 and 1.62 V to deliver industrially relevant current densities of 500 and 1000 mA cm^-2, respectively, with excellent durability for over 200 h, which is comparable to commercial electrolysis. Theoretical calculations reveal that the hierarchical heterostructure increases the electronic delocalization of the Fe and Ni catalytic centers, lowering the energy barrier of the rate-limiting step and promoting O₂ desorption. Finally, by implementing the catalysts in a solar-driven water electrolysis system, we demonstrate a record and durable solar-to-hydrogen (STH) conversion efficiency of up to 20.05%. This work provides a promising strategy for developing low-cost and high-efficiency bifunctional catalysts for a large-scale solar-to-hydrogen generation.