Few-layer MoAlB nanosheets with Al vacancies enhanced hydroxyl adsorption for improved water oxidation kinetics

Few-layer metal borides (MBenes) have attracted much attention in electrocatalytic energy conversion due to the unique physical features, but the present studies are confined to the related bulk materials and the structure-activity relationship is unclear. Here, we successfully synthetized a few-layer exfoliated MoAlB (denoted as EMAB) material as an oxygen evolution reaction (OER) catalyst through a modified etching and exfoliation method to remove the Al atoms and separate the layers. The enhanced hydroxyl adsorption and reduced surface valence of Mo are responsible for the improved OER activity and stability. Density functional theory simulations indicate the hydroxyl adsorption sites are adjusted when removing the Al atoms. The reactive interface for the MAB is the Al layer, while introducing Al vacancies, the hydroxyls prefer to be firstly adsorbed on the Mo sites, and further adsorbed on Al sites, so the energy barrier is largely reduced to accelerate the reaction. This work expands the OER application and mechanism study of MBenes.