Rational design of core-shell-structured CoPx@FeOOH for efficient seawater electrolysis

[Display omitted] •Core-shell-structured CoPx@FeOOH is designed as an efficient catalyst for selective seawater oxidation.•This hierarchical catalyst has high conductivity, large surface area, and improved turnover frequency, which lead to superb OER performance.•The strong chloride corrosion resistance and enhanced chemical stability help it work well in alkaline seawater electrolyte.•The CoPx||CoPx@FeOOH pair requires low voltages to attain high current densities for overall seawater splitting with high Faradaic efficiency and excellent stability. Hydrogen generation by seawater electrolysis is a sustainable approach to renewable-energy conversion which requires efficient catalyst to address challenges such as competing chlorine evolution reaction, chloride corrosion, and catalyst poisoning. Here, core-shell-structured CoPx@FeOOH is designed for selective OER in seawater. This catalyst has high conductivity, large surface area, improved turnover frequency, and optimal absorption energy to OER intermediates, which together lead to excellent catalytic activity. The enhanced chemical stability and corrosion resistance ensure its catalytic performance in seawater. Specifically, it requires overpotentials of 283 and 337 mV to attain current densities of 100 and 500 mA cm−2, respectively, in 1 M KOH seawater, with durability over 80 h of continuous testing without producing any hypochlorite. The CoPx||CoPx@FeOOH pair requires voltages of 1.710 and 1.867 V to attain current densities of 100 and 500 mA cm−2 with a high Faradaic efficiency, showing its great promise for fuel-gas production from seawater.