Modification of CoFe Prussian Blue Structure by N₂ Plasma for Enhanced Electrocatalysis

The efficiency of hydrogen production via water electrolysis is severely constrained by the sluggish reaction kinetics of the oxygen evolution reaction (OER). Herein, we constructed a nitrogen-doped CoFe Prussian blue analog (CoFePBA-N) electrocatalyst with a nanosheet-assembled cubic architecture by plasma. Plasma treatment induces morphological reconstruction and introduces nitrogen dopants and abundant vacancies, which not only increase the number of exposed active sites but also modulate the electronic structure of Co/Fe centers. Consequently, the optimized CoFePBA-N catalyst achieves a current density of 500 mA cm^-2 at low overpotentials of 322, 344, and 374 mV in alkaline freshwater, alkaline simulated seawater, and alkaline natural seawater, respectively. Furthermore, the catalyst maintains stable operation for over 300 h in alkaline freshwater and nearly 270 h in alkaline natural seawater, exhibiting exceptional durability. The enhanced catalytic performance is attributed to the synergistic effects of nitrogen doping, vacancies, and improved charge-transfer capability. This study provides an effective approach for modulating the electronic structure of Prussian blue analogs, thereby enabling efficient alkaline water and seawater electrolysis.