Partial sulfidation strategy to NiCo-LDH@NiCoS coupled with NiFe-LDH for highly efficient overall water splitting

The development of cost-effective and highly efficient bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media plays a crucial role in advancing renewable energy conversion technologies. In this study, we successfully constructed a three-dimensional (3D) composite on nickel foam (NF) by coupling NiFe-LDH nanosheets with NiCoS nanoparticles decorated NiCo-LDH nanosheets, resulting in a NiCo-LDH@NiCoS@NiFe-LDH hierarchical heterostructure. The resulting composite exhibits abundant heterogeneous interfaces and a well-defined nanosheet array structure, allowing for numerous exposed surface active sites and open channels. The strong synergistic effect among its various components allows the heterogeneous structure to effectively optimize the electronic structures of the metal active sites. Consequently, the NiCo-LDH@NiCoS@NiFe-LDH composite demonstrated remarkable catalytic activity towards OER, achieving current densities of 50 and 100 mA cm−2 at overpotentials as low as 209 and 224 mV, respectively. This result manifests a substantial improvement over recently developed electrocatalysts based on earth-abundant elements. Additionally, the NiCo-LDH@NiCoS@NiFe-LDH composite can efficiently catalyze HER in an alkaline medium, with a low overpotential of 93 mV at 10 mA cm−2 in 1 M KOH solution. Moreover, the electrolytic cell utilizing NiCo-LDH@NiCoS@NiFe-LDH as the electrodes could realize overall water splitting with an ultralow cell voltage of 1.55 V at 10 mA cm−2, and excellent electrochemical stability. These findings underscore the potential for developing high-performance bifunctional electrocatalysts with significant implications for large-scale commercial applications of renewable energy technologies.