In Situ Adsorption of a Lewis Base Triggers Selective Seawater Oxidation Based on the Lattice Oxygen-Mediated Mechanism

During seawater electrolysis, the anodic oxygen evolution reaction (OER) is invariably confronted with an inescapable challenge: side reactions instigated by chloride ions and the poisoning of catalytically active sites. To address this, we put forward a strategy of doping high-valence metal Mo into Ni(OH)2 to achieve high selectivity and activity of the OER in alkaline seawater. In situ characterization, along with theoretical calculations, demonstrates that Lewis bases (MoO42–) are generated through Mo dissolution within the catalyst and subsequently adsorbed in situ on the catalyst surface. Additionally, the Ni(OH)2 with Mo doping realizes a more rapid phase transformation of Ni(OH)2 and the redistribution of local charge and triggers the lattice oxygen-mediated mechanism. This process elevates the active site to a higher oxidation state (Ni3+x) and endows the active site with a high selectivity toward OH–. In an alkaline seawater anion-exchange membrane electrolyzer, NiOOH-MoO42– as anode achieves good durability, with the system remaining operational for over 180 h at a current density of 500 mA cm–2. This research presents an efficient approach for the straightforward and expeditious fabrication of high-oxidation-state Ni-based electrocatalysts featuring an adsorbed Lewis base (MoO42–), which holds good promise in steering the advancement of seawater electrolysis technology.