Electron delocalization state-induced intermediate selective adsorption for efficient chlorine evolution in seawater electrolysis

Co3O4 is a promising catalyst for the chlorine evolution reaction (CER) in seawater; however, its CER selectivity is compromised by the adsorption of the competitive oxygen evolution reaction intermediate (OH−) at Co sites. Inspired by the hard-soft acid-base (HSAB) theory, this study proposes incorporating early transition metal sites (V) with a low degree of electron delocalization into Co3O4 to modulate the selective adsorption of reactants on catalytic sites. Experimental and theoretical calculations reveal that V incorporation facilitates the electron accumulation at the Co site, significantly strengthening the interaction between Co and Cl−. Meanwhile, the loss of electrons from V sites generates a more localized electronic state that preferentially adsorbs OH−, thus reducing the Co-OH interaction and releasing more Co sites for Cl− adsorption. Therefore, Co2VO4 exhibits a high CER selectivity of 92.3% and maintains one of the highest stabilities over 300 h in natural seawater. The resulting half-flow cell achieves ∼100% disinfection efficiency in seawater, validating the HSAB theory-based design strategy and offering new guidance for developing highly selective seawater CER catalysts.