Transition metal doping enhances pseudocapacitive energy storage in monoclinic molybdenum dioxide

Abstract

Pseudocapacitive supercapacitors have garnered significant research attention in recent years due to their advantage of simultaneously possessing high energy density and high power density. Molybdenum-based metal oxides exhibit high specific capacity and low cost, among which MoO2 demonstrates relatively lower specific capacity but superior electrical conductivity. This study designs transition metal doping (Fe2+, Co2+, Ni2+, Cu2+, Zn2+) to enhance the capacitive performance of MoO2. Characterization results reveal that doping does not alter the crystal structure of MoO2 but influences its microscopic morphology, thereby significantly modulating its electrochemical properties. Electrochemical tests indicate that the specific capacity of pristine MoO2 is 129.6 F g-1 at a current density of 0.5 A g-1. After transition metal ion doping, both the current response and specific capacity of MoO2 are significantly improved. Notably, Fe2+-doped MoO2 achieves a specific capacity of 206.4 F g-1, corresponding to an enhancement of 58.8% compared to the undoped sample.