Stable α-MoO3 Electrode with a Widened Electrochemical Potential Window for Aqueous Electrochemical Capacitors

alpha-MoO3 is a promising electrode material for electrocapacitive energy storage. However, it has poor stability in aqueous electrolytes due to dissolution in water. Here, we demonstrate that an alpha-MoO3 electrode prepared using the electrochemical deposition method is stable over a wide potential window of 2.2 V in a neutral aqueous electrolyte. The improved stability of the alpha-MoO3 electrode in water is attributable to enhanced electron conductivity, which minimizes the polarization-induced structural collapse, and the dense microstructure of the alpha-MoO3 film electrode. The widened potential window is related to the electrocatalytic inactivity of the alpha-MoO3 toward water electrolysis and the high overpotentials of the neutral electrolyte toward H-2 and O-2 evolution reactions. A symmetric supercapacitor cell fabricated with the electrochemically deposited alpha-MoO3 electrode delivers a specific energy as high as similar to 22 Wh/kg at a specific power of similar to 301 W/kg. This work demonstrates that the electrochemical deposition method is a viable approach to fabricating alpha-MoO3 electrodes for aqueous electrochemical energy storage.

Automated summary

This study demonstrates that an alpha-MoO3 electrode prepared using the electrochemical deposition method exhibits stability in neutral aqueous electrolytes and a wide potential window, attributed to enhanced electron conductivity and dense microstructure. The widened potential window is linked to the electrocatalytic inactivity of alpha-MoO3 towards water electrolysis and high overpotentials of the neutral electrolyte for H-2 and O-2 evolution reactions.