Effect of proton irradiation on electrocatalytic properties of MnO₂ for oxygen reduction reaction

Significant efforts have been made to enhance the poor intrinsic electrocatalytic activity of MnO₂ toward the oxygen reduction reaction (ORR) for practical applications in fuel cells and metal-air batteries. However, the main bottleneck problems of the MnO₂ catalyst for the ORR include the poor conductivity and the low activity compared to state-of-the-art Pt/C. Here, high power proton particles (14 MeV) were irradiated on MnO₂, and numerous oxygen vacancies were introduced into the surface of MnO₂ by decomposing water radiolytically along the proton beam. Compared with the pristine MnO₂, the proton-treated MnO₂ showed a much higher current density of -4.6 mA cm^-2 at 0.65 V vs. reversible hydrogen electrode (RHE). The proton-treated MnO₂ exhibited excellent catalytic durability, maintaining 95% of its activity after a 10000 s chronoamperometric stability test. This outstanding ORR performance and stability can be attributed to the improved physicochemical properties resulting from the proton beam irradiation. This study provides a novel approach for the generation of oxygen vacancies by proton irradiation, improving the catalyst for use as an advanced electrode material.