Efficient and stable neutral seawater splitting achieved via strong-proton-adsorption in Pd-O-Co collaborative coordination

Abstract

Direct electrolysis of pH-neutral seawater for hydrogen generation is a promising method for storing renewable energy. However, the oxygen evolution reaction (OER) faces a selectivity challenge, competing with chlorine evolution and confronting severe corrosion issues of the electrode. Here, we have synthesized ultrathin, polycrystalline, porous Co3O4 nanosheets with Pd single atoms (PdSA-Co3O4) for efficient and stable pH-neutral seawater decomposition. The octahedral Pd-O-Co active unit, generated by the synergistic coordination of the Pd single atom strong proton adsorption (SPA) material with Co3O4 nanosheets, resulted in PdSA-Co3O4 have activities 3, 5, and 31 times higher than Co3O4, IrO2, and commercial Co3O4, respectively. It also remained stable in pH-neutral seawater for 80 h. Operando in situ Raman spectroscopy combined with density functional theory calculations showed that synergistic interactions between the strong proton adsorption of Pd single atoms and the active site Co enhanced the adsorption of intermediates and significantly reduced the free energy of adsorption at the rate-determining step (O*→OOH*). The Pd-O-Co active units inhibited the transformation of the dynamic structure of the Co3O4 substrate and reduced the corrosive effect of Cl ions during the OER process.