Fabrication of MoOx Film as a Conductive Anode Material for Micro-Supercapacitors by Electrodeposition and Annealing

An annealing process in reductive atmosphere of flowing H-2/Ar improves the rate capability and cycling stability of electrodeposited MoOx film, which is favorable for its future application as micro-electrode for micro-supercapacitors. MoO2 grains were found in the films annealed at temperatures above 350 degrees C, and the content of MoO2 nanocrystallites was controlled by adjusting the annealing time. After annealing for 1.5 h at 350 degrees C, the 63 nm thick film exhibited the best electrochemical property, with a high volumetric capacitance of 594 F cm(-3) at 20 mV s(-1), good rate capability with a relaxation time constant of 11 ms, and excellent cycling stability of 99% capacitance retention after 4000 cycles. This could be attributed to the combination of nanocrystalline MoO2, which is electronically conductive, and amorphous MoOx (x>2), which is pseudocapacitive in aqueous electrolyte. (C) 2014 The Electrochemical Society. All rights reserved.