A hydroxychloride-triggered spinel composite electrode for energy-efficient and long-lasting hydrogen production from brine electrolysis

Abstract

Integrating the inherent strengths of distinct functional materials to engineer advanced composite electrodes for brine oxidation is crucial for advancing sustainable technology for hydrogen production from seawater electrolysis. The general approach to developing efficient electrodes is to combine a catalyst and a support material to leverage catalyst-support interactions. In this study, a trigger-catalyst composite electrode design was put forward. Specifically, highly oxidation-prone Co₂(OH)₃Cl was employed as a trigger, combined with stable CoFe₂O₄ catalysts to engineer a Co₂(OH)₃Cl@CoFe₂O₄ composite electrode for active and stable brine oxidation. In situ Bode plots and first principles evidence revealed that the oxidation of Co₂(OH)₃Cl components promoted the activation of CoFe₂O₄ catalysts at low potentials to drive the oxygen evolution reaction (OER) in brine electrolytes. As a result, the Co₂(OH)₃Cl@CoFe₂O₄ electrode exhibited a low overpotential of 295 mV at 100 mA cm⁻² in a brine electrolyte, which represents an outstanding performance, among the best Co-based electrodes for OER to date. More importantly, the alkaline seawater electrolyzer assembled using the Co₂(OH)₃Cl@CoFe₂O₄ anode and a commercial Ni mesh cathode showed stable hydrogen production performance for 1000 h at 100 mA cm⁻² and 50 h even at 1 A cm⁻², suggesting the progress made using the Co₂(OH)₃Cl trigger/CoFe₂O₄ catalyst composite electrode in driving hydrogen production from brine electrolysis.