Enhancing oxygen reduction activity of α -MnO 2 by defect-engineering and N doping through plasma treatments

MnO 2 is a promising catalyst for oxygen reduction and metal–air batteries due to the natural abundance, low cost and nontoxicity. Improving its activity is an important challenge for its large-scale commercialization. Defect engineering and heteroatom doping are the most effective means and can be easily operated through plasma treatment at different atmospheres. In this work, defects on MnO 2 are manufactured via rapid plasma treatment at Ar atmosphere while both defects and N-doping are simultaneously fabricated at N 2 atmosphere. N–MnO 2 exhibits a greatly enhanced ORR activity with a half-wave potential of 0.84 V, a limiting current density of 6.7 mA cm −2 and the number of transferred electrons of 3.9. In neutral Mg-air battery, N–MnO 2 -based battery exhibits a max power density of 124.3 mW cm −2 at a current density of 255.4 mA cm −2 and excellent stability under different working condition. These superior performances of N–MnO 2 to Ar–MnO 2 and pristine α -MnO 2 demonstrate that the defects and N-doping by plasma treatment at N 2 atmosphere significantly enhance the oxygen reduction activity. This work reveals the relationship between microstructure and oxygen reduction reaction and supplies a new idea for the developing economical and efficient oxygen reduction reaction catalysts for metal–air batteries. Graphical Abstract