Enhancing unidirectional charge transfer between vacancy-mediated unilamellar LDH nanosheets and electric conductive counterparts toward overall water splitting

Abstract

Atomic vacancy-containing NiFe layered double hydroxide (NiFe-LDH^V) nanosheets were electrostatically assembled with electric conductive reduced graphene oxide (rGO) and MoS₂ into heterostructured composites of NiFe-LDH^V/rGO and NiFe-LDH^V/MoS₂, respectively. The introduction of vacancy not only provides ion transport channels, but also promotes unidirectional electron transfer from NiFe-LDH^V to the conductive counterparts at the heterointerface, thereby improving charge transfer and adsorption of intermediates for efficient electrocatalysis. Compared to conventional NiFe-LDH, the vacancy-mediated interaction led to a stronger electronic coupling effect at the interface of the heterostructures. As a result, relatively low overpotentials were obtained on NiFe-LDH^V/rGO for OER and NiFe-LDH^V/MoS₂ for HER, respectively. A two-electrode electrolyzer with NiFe-LDH^V/rGO as the anode and NiFe-LDH^V/MoS₂ as the cathode was assembled for water splitting, attaining a current density of 10 mA cm⁻² at a small voltage of 1.50 V. The NiFe-LDH^V/rGO||NiFe-LDH^V/MoS₂ cell also demonstrated excellent stability at a high current density of 500 mA cm⁻². The current strategy of integrating vacancy-containing unilamellar LDH nanosheets with conductive counterpart materials provides new insights into designing highly active LDH-based heterostructures for various electrochemical and catalytic applications.