Morphology and Structural Regulation of S and Cr Co-doped FeOOH Nanoarray for Promoting Oxygen Evolution Reaction

Designing low-cost and environmentally friendly oxygen evolution reaction (OER) electrocatalysts to enhance the electrocatalytic water decomposition to produce hydrogen still faces great challenges. In this work, a feasible strategy for metallic/nonmetallic elements co-doping to boost the OER catalytic properties of iron oxyhydroxide is proposed. A series of S and Cr co-doped iron oxyhydroxides nanoarrays loaded on nickel foam (Sx,Cr-FeOOH/NF) were prepared by an electrodeposition–hydrothermal method. The optimized S0.1,Cr-FeOOH/NF exhibits a superior electrocatalytic OER performance with low overpotential (235 mV at 100 mA cm–2), highly outperforming commercial RuO2. Meanwhile, the overpotential of S0.1,Cr-FeOOH/NF increases by only 4 mV after 70 h of stability testing at 100 mA cm–2, demonstrating its durability. The nanoarray with ultrathin nanosheets of S0.1,Cr-FeOOH/NF regulated by S and Cr co-doping can offer abundant active sites and also facilitate mass transportation. The density functional theory (DFT) calculation results show that S and Cr co-doping modifies the electronic structure of S0.1,Cr-FeOOH/NF, which thus optimizes the adsorption energy toward the OER intermediates, promotes the transformation of *O to *OOH (rate-determining step), and thus accelerates the OER kinetics.