Sputtered Ag-doped NiO thin films: structural, optical, and electrocatalytic activity toward methanol oxidation

Abstract Significant research is being performed to find suitable electrocatalysts in alkaline direct methanol fuel cells. Despite tremendous improvements, producing non-Pt catalysts with great activity and high stability is still difficult. Herein, Ag-doped NiO thin films were deposited on fluorine-doped tin oxide (FTO) by the co-sputtering deposition method, utilizing various deposition times (200, 400, 600, and 800) seconds. The film thickness for the deposited films varied from 17, 35, 70, and 100 nm by increasing the deposition time from 200, 400, 600, to 800) seconds. The NiO–Ag-800 recorded the lowest band gap of 3.36 eV, whereas the NiO–Ag-200 recorded the highest band gap of 3.81 eV. The deposited thin films were used as electrocatalysts for methanol oxidation. Its physical properties facilitate the adsorbed reactions, allow for easier penetration of electrolytes, and help in rapid reaction kinetics. Moreover, because Ag–NiO is deposited on an FTO substrate with outstanding adhesion and excellent electric contact, it can be utilized; without adding any binder or conducting agents. The films displayed reduced onset potential for oxidation of the methanol, high current density, and long-term stability. The thickness of the thin film proved that it plays a role in electroactivity. The efficiency of the films increased with increasing thickness, where the Ag–NiO-800 record the lowest onset potential is 0.37 V vs. Ag/AgCl.