Effects of hydrogen etching on MnO₂ electrode materials for supercapacitors

Manganese dioxide (MnO₂) has received widespread attention as electrode materials in supercapacitors. In this work, the effects of hydrogen etching on MnO₂ deposited on nickel foam are studied. The specific capacitance before hydrogen etching is 400 F/g and goes up to 900 F/g at a current density of 2 A/g after hydrogen etching for 5 min. After 2000 operating cycles, the capacitance retention rate of the hydrogen-etched sample is 92% compared to 82% of the untreated sample. Hydrogen etching produces surface damage and defects such as many nanopores which enhance the capacitance properties. First-principles calculation confirms the experimental results indicating that the improved performance stems from the larger specific surface area on MnO₂ as well as stable defects created by hydrogen etching. The study demonstrates a simple and effective way to improve the properties of electrodes in supercapacitors.