Enhancing oxygen reduction activity of α-MnO2 by defect-engineering and N doping through plasma treatments

MnO2 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 MnO2 are manufactured via rapid plasma treatment at Ar atmosphere while both defects and N-doping are simultaneously fabricated at N-2 atmosphere. N-MnO2 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-MnO2-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-MnO2 to Ar-MnO2 and pristine alpha-MnO2 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. [GRAPHICS]