Lattice‐Strain Engineering of Homogeneous NiS 0.5 Se 0.5 Core–Shell Nanostructure as a Highly Efficient and Robust Electrocatalyst for Overall Water Splitting

Abstract Developing highly‐efficient non‐noble‐metal electrocatalysts for water splitting is crucial for the development of clean and reversible hydrogen energy. Introducing lattice strain is an effective strategy to develop efficient electrocatalysts. However, lattice strain is typically co‐created with heterostructure, vacancy, or substrate effects, which complicate the identification of the strain‐activity correlation. Herein, a series of lattice‐strained homogeneous NiS x Se 1− x nanosheets@nanorods hybrids are designed and synthesized by a facile strategy. The NiS 0.5 Se 0.5 with ≈2.7% lattice strain exhibits outstanding activity for hydrogen and oxygen evolution reaction (HER/OER), affording low overpotentials of 70 and 257 mV at 10 mA cm −2 , respectively, as well as excellent long‐term durability even at a large current density of 100 mA cm −2 (300 h), significantly superior to other benchmarks and the precious metal catalysts. Experimental and theoretical calculation results reveal that the generated lattice strain decreases the metal d‐orbital overlap, leading to a narrower bandwidth and a closer d‐band center toward the Fermi level. Thus, NiS 0.5 Se 0.5 possesses favorable H* adsorption kinetics for HER and lower energy barriers for OER. This work provides a new insight to regulate the lattice strain of advanced catalyst materials and further improve the performance of energy conversion technologies.