Mn-doped RuO2 nanocrystals with abundant oxygen vacancies for enhanced oxygen evolution in acidic media

Abstract

The substantial demand for renewable hydrogen energy, known for its low pollution, has accelerated in-depth research into green hydrogen production technology and proton exchange membrane water electrolyzer (PEMWE). The crux of advancing PEMWE technology lies in developing a catalyst that maintains high activity at elevated current densities, resists corrosion, and operates stably under acidic conditions. In our work, the synthesis of an Mn–RuO₂-120(NaNO₃) catalyst is reported, enriched with oxygen vacancy defects through the molten salt method, using an Mn–hexamethylenetetramine metal–organic framework as the precursor. Physical characterization methods, such as synchrotron radiation, indicate that the presence of oxygen vacancies reduces the Ru/O coordination ratio, thereby enhancing the charge transfer efficiency of the catalyst. Theoretical calculations show that the synergistic effects from Mn doping and oxygen vacancies can regulate the binding energy of *OOH at Ru CUS, effectively lowering the energy barrier of OER intermediates, thus boosting electrochemical OER processes. The optimized catalyst demonstrates an overpotential of 189 mV at a current density of 10 mA cm⁻². Meanwhile, the Mn–RuO₂-120(NaNO₃) catalyst is capable of operating for 200 hours on Ti felt and can maintain steady performance for 90 hours in a PEM electrolyzer. The activity performance evaluation of Mn–RuO₂-120(NaNO₃) in a PEM electrolyzer revealed that its potential reached 1.69 V at a current density of 1 A cm⁻².