Rational Design of Non-precious Metal Electrocatalysts for Alkaline Water Splitting

Abstract

Hydrogen (H2) has been regarded as the most promising energy carrier and is predicted to address global environmental challenges. Electrochemical water splitting has attracted considerable attention to producing hydrogen with high purity with the aid of renewable energy resources. However, the sluggish reaction kinetics of both anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER) lead to large energy consumption and low energy efficiency. Therefore, the development of non-precious metal electrocatalysts with superior activity and long-term durability is of great significance. First, the fabrication of LaCoO3 nanoarrays onto conductive nickel foam was achieved to optimise the OER performance. This strategy is demonstrated to be effective for enlarging the surface area with more active sites and improving surface wettability for gas bubbles release. Then, a highly active NiV oxyhydroxide was prepared by the in situ structural reconstruction of V-doped Ni2P pre-catalysts via an electrochemical oxidation approach. The boosted intrinsic activity is achieved by the construction of a disordered Ni structure by partial dissolution of V dopants with optimised electronic structure. The remaining V dopants greatly enhanced the kinetics for the generation of intermediates and increase the content of the active β-NiOOH phase, contributing to OER activity enhancement. Furthermore, a heterostructured HER catalyst has been developed by taking advantage of both heteroatoms doping and heterointerfaces effect. The strong coupling effects between the two phases enable electron redistribution at the interface with the regulation of catalytic active sites. The synergistic effects between doping and interface engineering contribute to the enhanced HER performance and stability in alkaline media. Finally, a dual atom doping strategy is proposed to induce an electron delocalisation of the host nickel phosphide as a novel HER catalyst. The observed synergistic effect of the dopants is responsible for ensuring Ni active sites with high intrinsic activity. Efforts have also been made to demonstrate the potential application of as-prepared catalysts for hydrogen production at anion exchange membrane water /seawater electrolysers.