Boosting the electrocatalytic performance of CuCo2S4 via surface-state engineering for ampere current water electrolysis applications.

[Display omitted] • A dual regulation strategy has been employed to create vacancies and the elevate intrinsic activity of the CCS/O v. • Small OER (383 mV) and HER (355 mV) overpotentials at 1000 mA cm−2 in 1 M KOH and excellent ion transport in various electrolytes. • DFT calculations reveal that excellent bifunctional OER/HER activities are due to a modulated valence state. • An electrolyzer cell exhibits a small cell voltage of 1.487 V in 6 M KOH and has good robustness against corrosive chlorine. For the efficient production of green H 2 on an industrial scale, developing durable, cost-effective electrocatalysts using earth-abundant transition-metals is crucial. Herein, we report a robust, bifunctional sulfurized CuCo 2 O 4 (CCS/O v) catalyst with engineered oxygen-vacancies, in which the metal catalyst is tunes to high valence state, significantly altering the intrinsic reaction kinetics and generating better catalytic activity for efficient ion transport in various electrolytes (neutral, seawater, alkaline simulated-seawater (ASW), and KOH). The optimized dual-strategy synthesized CCS/O v catalysts with hierarchical morphology exhibits modest overpotential of 383 and 355 mV at 1000 mA cm−2 for OER and HER, respectively, in 1 M KOH. Impressively, an electrolyzer cell (CCS/O v ||CCS/O v) demonstrates low cell-voltage of 1.487 V (6 M KOH), with excellent robustness in an ASW (1 and 2 M) environment against corrosive chlorine. The bifunctional CCS/O v ||CCS/O v catalyst outperforms a state-of-the-art paired Pt/C||RuO 2 catalyst and maintains the lowest potential response at up to 2000 mA cm−2, while demonstrating remarkably stable simultaneous O 2 and H 2 generation over 10 days at various current rates. Additionally, DFT calculations confirmed that CCS/O v catalysts demonstrate significantly enhanced HER and OER activities due to reduced H 2 O dissociation energy and strong intermediate binding energy, which is attributed to the anionic vacancy near Co3+. The excellent bifunctional performance of the hierarchical CCS/O v highlights its potential as non-precious catalyst with facile fabrication approach. [ABSTRACT FROM AUTHOR]