Ru/Rh Cation Doping and Oxygen-Vacancy Engineering of FeOOH Nanoarrays@Ti₃ C₂ T_x MXene Heterojunction for Highly...

Oxyhydroxides hold promise as highly-efficient non-noble electrocatalysts for the oxygen evolution reaction (OER), but their poor conductivity and structural instability greatly impede their progress. Herein, the authors develop a cation-doping and oxygenvacancy engineering strategy to fabricate Ru/Rh-doped FeOOH nanoarrays with abundant oxygen-vacancies in situ grown on Ti₃ C₂ T_x MXene (Ru/Rh-FeOOH@Ti₃ C₂ T_x ) as highly-efficient OER electrocatalysts. Benefiting from Ru/Rh-cation regulation, oxygenvacancy engineering, and heterojunction synergy between MXene and modulated FeOOH, the optimized Rh/Ru-FeOOH@Ti₃ C₂ T_x electrocatalysts exhibit excellent OER activities and remarkable stabilities with 100 h. Particularly, 3%Rh-FeOOH@Ti₃ C₂ T_x electrocatalyst only needs a 223 mV overpotential at 10 mA cm^-2 and 306 mV to reach 100 mA cm^-2 , which is superior to commercial IrO₂ catalyst and most reported oxyhydroxide-based electrocatalysts. Further, systematically theoretical caculation, kinetics, thermodynamics, and microstructural analysis verify that the integration of Ru/Rh-cation doping and oxygen vacancy obviously enhances the intrinsic conductivity and lattice defects of FeOOH and expose more active sites, thereby decreasing the adsorption/desorption energy barrier and activation energy, and improving the specific activity and catalytic kinetics of electrocatalysts, whereas in situ hybridization with MXene strengthens the structural stability. This work clearly confirms that cationdoping and oxygen-vacancy engineering offers a joint strategy for the electronic structure modulation and design of highly-efficient inexpensive OER electrocatalysts.