Surface defect engineering of sub-2 nm NiFe layered double hydroxide with multiple vacancies induced by alkaline ionic liquid enabling enhanced water oxidation

Abstract

Surface defect engineering constitutes a promising strategy for optimizing surface electronic configuration and addressing the sluggish kinetics of the oxygen evolution reaction (OER). However, highly efficient creation of multiple vacancies on a catalyst's surface and investigating their effects on the OER remain highly challenging. Herein, we present the successful fabrication of sub-2 nm NiFe layered double hydroxides (LDHs) with high yields of surface metal and oxygen multivacancies through an electron-rich modifier alkaline ionic liquid (AIL). Simultaneously, the AIL can facilitate the nucleation and prevent the growth process of the NiFe LDH, thereby creating multivacancies in sub-2 nm NiFe LDH. Furthermore, mechanistic investigations further prove that the AIL modification strategy can efficiently optimize electronic redistribution and reduce the d-band center, weakening the adsorption of oxygenated intermediates and enhancing OER kinetics. Consequently, the energy barrier of the rate-determining step for the formed multiple vacancy-rich NiFe LDH is significantly reduced, resulting in a low overpotential of 180 mV at 10 mA cm⁻². Remarkably, the NiFe LDH/AIL-0.1 with optimal AIL loading achieves outstanding mass activity (3296 A g_Metal⁻¹), outperforming most-often reported catalysts, leading to significant activity (η₁₀/η₅₀ ∼ 235/275 mV) and outstanding durability (>100 h). This design strategy using ionic liquid can guide the surface defect engineering of other inorganic nanomaterials with abundant multiple vacancies that efficiently catalyze key energy technologies.