Defective NiMn LDH prepared using hydrogen evolution coupled electrodeposition for highly efficient oxygen evolution reaction

Defect engineering is widely acknowledged as an effective strategy for exposing catalytically active sites. However, many post-treatment approaches tend to be intricate and compromise the stability of catalysts, limiting the reusability of the defective materials. In this study, we introduce a simple and novel strategy for preparing defective materials for the first time, known as hydrogen evolution coupled electrodeposition (HECED). In the HECED method, the hydrogen evolution reaction (HER) and the hydroxide deposition reaction are synergistically coupled. This allows for the direct preparation of defective materials without the need for subsequent secondary processing. Prepared through the direct synthesis strategy, the D-NiMn LDH catalyst exhibits highly promising performance and stability for the oxygen evolution reaction (OER) in alkaline media. Subsequently, FeS nanoparticles are loaded onto the D-NiMn LDH to create a D-NiMn LDH/FeS heterostructure, which demonstrates an ultralow overpotential of 184 mV at 10 mA cm-2 and fast reaction kinetics of 49 mV dec-1. This catalyst is currently one of the most attractive options for the OER. Significantly, by utilizing D-NiMn LDH as the cathode and D-NiMn LDH/FeS as the anode, the overall water cell can achieve 10 mA cm-2 at 1.50 V. Our investigation reveals that during the OER, D-NiMn LDH/FeS undergoes self-reconstruction, leading to the formation of SOx-FeNiMn (oxy)hydroxides, which act as active sites and facilitate the OER process. Our study not only presents a novel and simple method for the direct synthesis of defective NiMn LDH, but also provides new insights into designing stable and reusable defective materials. A defective NiMn LDH catalyst was synthesized using a hydrogen evolution coupled electrodeposition method, demonstrating excellent oxygen evolution reaction catalytic performance after forming a heterostructure with FeS.