2D Layered Material Interface Confined Dynamically in-Situ Generated Ni(OH)2 Triggers Ultrafast Oxygen Evolution

Abstract

Basic insights into the structural evolution of oxygen electrocatalysts under operating conditions are of substantial importance for designing water oxidation catalysts. Recently, the development of potent oxygen evolution reaction (OER) electrocatalysts has trigger researcher’s attention. Conversely, the design of active and stable catalyst under alkaline media is a substantial issues and challenges of the area due to the poor cyclability of catalysts and the sluggish water dissociation kinetics. Our work reports the design and synthesis of a two-dimensional (2D) SnS2 confined in-situ generated Ni(OH)2 nanoparticle electrocatalyst, which accelerates water oxidation and exhibits long term durability in alkaline solutions, leading to significant improvement in OER performance. A two-step method was used to synthesize the electrocatalyst, starting with the lithium intercalation of exfoliated SnS2 nanosheets followed by Ni2+ exchange in alkaline media to form SnS2 intercalated with Ni(OH)2 nanoparticles (denoted Ni-Ex-SnS2), which was fully characterized by in-situ X-ray absorption spectroscopy for two cycles. Electrochemical tests indicated that the electrocatalyst exhibits superior OER activity and excellent stability, with an onset overpotential and Tafel slope as low as 17 mV and 42 mV dec−1, respectively, which are among the best values reported in alkaline media. Furthermore, density functional theory calculations show that the co-joint roles of Ni(OH)2 nanoparticles and SnS2 nanosheets result in the excellent activity of the Ni-Ex-SnS2 electrocatalyst, and the good stability is attributed to the confinement of the in-situ generated Ni(OH)2 nanoparticles. The combination of electrochemical measurement, operando X-ray absorption spectroscopy and density functional theory (DFT) calculations revealed that the in-situ generated and confined Ni(OH)2 as the critical active species via the principle of nano-confinment and in-situ generations. This work proposes the plausible catalytic reaction pathway and mechanism.