Plasma enhanced oxygen and hydrogen evolution reaction efficiency of titanium vanadate thin film electrodes fabricated by RF magnetron sputtering for green hydrogen production

This research analyses titanium vanadate (TiVO4) thin films, which serve as bifunctional catalysts on electrodes for the production of green hydrogen. To achieve the required catalytic activity, the thin film’s surface was modified under argon and nitrogen plasma (15 and 30 min). The treatment resulted in contact angle measurements indicating greater surface hydrophilicity than in nontreated films, thereby promoting electrolyte interactions. The electrochemical assessment exhibited significant bifunctional activity, with oxygen evolution reaction (OER) overpotentials of 520 mV (uncorrected) and 480 mV (IR-corrected), and a decrease in Tafel slope from 120 to 110 mV. The hydrogen evolution reaction (HER) overpotential was 208.2 mV (uncorrected) and 165 mV (iR corrected), with slopes decreasing from 350 to 88 mV. Treatments using plasma further improved activity, with durations of 15 and 30 min for both argon and nitrogen. The 30 min duration yielded better OER, while HER performed better. Argon-30 min achieving the best HER overpotential (38.05 mV uncorrected and 20.09 mV iR corrected), and nitrogen-30 min providing the best OER overpotential (295 mV uncorrected and 142 mV iR corrected) with a Tafel slope of 65 mV. However, for argon at 15 min, the OER shows an overpotential of 400 mV; after IR correction, it is 175 mV. For nitrogen, the overpotential is 415 mV for 15 min; after IR correction, it is 400 mV. Hence, the 30 min duration indicates a better overall performance of OER and HER. Electrochemical impedance spectroscopy demonstrated considerable enhancements in charge transfer for the plasma-treated samples. Chronoamperometry results demonstrated long-term stability, and comparing linear-sweep potential measurements before and after the stability test revealed surface activation, with the HER overpotential decreasing from 208 to 88.5 mV. Overall, these findings show that plasma-enhanced RF-sputtered TiVO4 films exhibit promising efficiency, stability, and hydrophilicity as electrodes for the production of green hydrogen.