Uniform P-Doped MnMoO4 Nanosheets for Enhanced Asymmetric Supercapacitors Performance

Manganese molybdate has garnered considerable interest in supercapacitor research owing to its outstanding electrochemical properties and nanostructural stability but still suffers from the common problems of transition metal oxides not being able to reach the theoretical specific capacitance and lower electrical conductivity. Doping phosphorus elements is an effective approach to further enhance the electrochemical characteristics of transition metal oxides. In this study, MnMoO4·H2O nanosheets were synthesized on nickel foam via a hydrothermal route, and the MnMoO4·H2O nanosheet structure was successfully doped with a phosphorus element using a gas–solid reaction method. Phosphorus element doping forms phosphorus–metal bonds and oxygen vacancies, thereby increasing the charge storage and conductivity of the electrode material. The specific capacitance value is as high as 2.112 F cm−2 (1760 F g−1) at 1 mA cm−2, which is 3.2 times higher than that of the MnMoO4·H2O electrode (0.657 F cm−2). The P–MnMoO4//AC ASC device provides a high energy density of 41.9 Wh kg−1 at 666.8 W kg−1, with an 84.5% capacity retention after 10,000 charge/discharge cycles. The outstanding performance suggests that P–MnMoO4 holds promise as an electrode material for supercapacitors.