Band gap engineering of MnO2 through in situ Al-doping for applicable pseudocapacitors

Band gap engineering was achieved by in situ doping method for high electrical conductivity and chemical activity of MnO2. By in situ releasing and adsorption during electrodeposition, Al3+ with close ion radius to Mn4+ could replace the position of Mn4+ in MnO2. The in situ doping process brings impurity level in MnO2 and changes the energy band structure. The narrower band gap of MnO2 after Al doping with higher electron concentration on conduction band could improve the conductivity of MnO2. The specific capacitance of Al-doped MnO2 achieves 430.6 F g(-1) which is almost 2.5 times of the capacitance of initial MnO2 (177 F g(-1)), shedding light on its practical applications.