Synergistic Cr doping engineering modulates interfacial built-in electric field and lattice oxygen activation for enhanced electrocatalytic water splitting.

The design of high-quality bifunctional catalyst is the hinge to promoting the development of hydrogen production technology. Doping engineering has been validated as an effective modification strategy for optimizing the intrinsic activity of the catalyst. Herein, a FeNiS@Cr-NiFe LDH heterostructure electrocatalyst with an enhanced built-in electric field (BIEF) and activated lattice oxygen is reported. Cr doping significantly reduces the activation barrier of lattice oxygen and promotes the dynamic reconstruction of the oxygen coordination environment. This process drives the transformation of the oxygen evolution reaction (OER) mechanism into a kinetically favorable lattice oxygen mechanism (LOM), which allows the catalyst to exhibit outstanding OER performance. Additionally, the enhanced BIEF improves the driving force for the directional movement of electrons, accelerating the supply of electrons in the Volmer step of the hydrogen evolution reaction (HER) mechanism, thereby optimizing the HER activity of the material. Accordingly, the FeNiS@Cr-NiFe LDH electrocatalyst displays outstanding OER (η = 217 mV, η = 232 mV) and HER (η = 162 mV, η = 222 mV) performance, as well as superior catalytic stability. This study focuses on the regulation of BIEF and activation of lattice oxygen, which offers a fresh perspective into the design of bifunctional catalysts based on BIEF and LOM.