Improving C-N-FeOx Oxygen Evolution Electrocatalysts through Hydroxyl-Modulated Local Coordination Environment

Ultrafine FeOx in the sub-nanometric or atomic scale is one of the promising catalysts for boosted oxygen evolution reaction (OER) activity, although there is further potential for improvement in comparison to commercial catalysts. Recent studies show that hydroxyl modification on the surface of catalysts can ameliorate hydrophilicity and catalytic activity, thus helping to bring such catalysts closer to scale-up and commercialization stages. To deeply understand the effect of hydroxyl, atomic-level dispersed FeOx in porous carbon nitride (CN-FeOx) was proposed through a spatially confined approach, which involved an in situ coordination effect between resorcinol and Fe ions. After hydroxyl modification, the generated CN-FeOx-OH hybrid material displayed significantly enhanced mass activity compared to CN-FeOx and commercial RuO2 (0.16 A/mgmetal) under an overpotential of 350 mV versus RHE. Additionally, the improved stability of CNFeOx-OH suppresses migration and aggregation. The DFT calculations revealed a distinct catalytic mechanism in which the active center composed of multisites modified by hydroxyl exhibited a strong synergistic effect to modulate the adsorption behaviors of OH and O intermediates, which possessed the optimal adsorption energy for enhanced activity as compared with a single site in the CN-FeOx-OH and CN-FeOx, respectively. The adopted strategies in this paper can effectively promote the application of Fe-based catalysts in OER.