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.
Teng et al. (2025) studied this question.