Boosting the bifunctionality and durability of cobalt-fluoride-oxide nanosheets for alkaline water splitting through nitrogen-plasma-promoted electronic regulation and structural reconstruction

Designing cost-effective and durable bifunctional electrocatalysts with high activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for large-scale hydrogen production through water splitting. However, many electrocatalysts undergo surface or bulk reconstruction, leading to an unstable catalytic activity. In this study, we present a facile N₂ plasma strategy to enhance the electrocatalytic activity of cobalt-fluoride-oxide (CoFO, herein NCoFO) nanosheets while maintaining reasonably stable performance. The optimized NCoFO nanosheets grown on carbon cloth through a 60 s N₂ plasma treatment (NCoFO/CC-60) exhibit remarkable performance with low overpotentials of 203 mV and 230 mV at 10 mA cm^-2 for the HER and the OER, respectively. Density functional theory calculations revealed that the enhanced catalytic performance is attributed to the regulated local electronic configuration resulting from plasma treatment. Furthermore, the assembled alkaline electrolyzer NCoFO/CC-60||NCoFO/CC-60 requires an extremely low voltage of 1.48 V to attain 10 mA cm^-2 for over a 150 h operation, which is superior to the values obtained for Pt/C||RuO₂ (1.50 V) and CoFO/CC||CoFO/CC (1.55 V).