Multifunctional monoclinic VO2 nanorod thin films for enhanced energy applications: Photoelectrochemical water splitting and supercapacitor

Abstract

Monoclinic VO2 nanorod thin films were deposited on indium-tin-oxide-coated glass substrates using radio-frequency reactive magnetron sputtering at a substrate temperature of 300 degrees C and various O-2 flow rates. The thin films were characterized via standard analysis techniques. The VO2 thin films exhibited a highly crystalline monoclinic phase with an indirect band gap of similar to 1.73 eV. At optimized O-2 flow rate (4 sccm), the thin films was observed nanorod structures, exhibited a remarkable photocurrent of -0.08 mA cm(-2) during photoelectrochemical water splitting in the visible region. Electrochemical performance tests of the nanorod films revealed a specific capacitance of similar to 486 mF cm(-2) at a scan rate of 10 mVs(-1). In addition, amperometric I-t curves showed that VO2 thin film electrodes were highly stable during the photo-oxidation process. The nanorod films also exhibited a good specific capacitance of similar to 120 mF cm(-2) after 5000 cycles at a scan rate of 100 mVs(-1). The photocurrents during photoelectrochemical water splitting and the specific capacitance of VO2 thin films deposited at O-2 flow rates of 2 and 6 sccm were 0.06 and 0.07 mA cm(-2) and 398 and 37 mF cm(-2), respectively. The films deposited under Ar at 8 sccm and O-2 at 4 sccm showed the highest photoelectrochemical water splitting performance and specific capacitance, owing mainly to their nanorod-like morphology.