NiO-Ru/RuO₂@Polyoxovanadate for the Catalytic MOR and OER in an Alkaline Medium

A Ni–Ru-based electrocatalyst combined with polyoxovanadate (POV) was found to show superior activity in the methanol oxidation reaction (MOR), suppressing the oxygen evolution reaction (OER). The role of POV was evaluated by comparing the activity with two other catalysts without POV. The NiO-Ru/RuO2 catalyst decorated with POV exhibited both OER and MOR activity in an alkaline medium with an onset potential of 1.531 ± 0.002 vs RHE and 1.370 ± 0.001 V vs RHE (at 50 mV s–1), respectively. The other two synthesized Ni–Ru-based catalysts, although they showed OER and MOR activity, were found to be inferior in the MOR in terms of the onset potential and current density compared to the similar catalyst modified with POV. However, it was observed that the Ni(OH)2-RuO2 exhibited better OER activity without POV. The low Tafel slope value of 112 mV dec–1 in the MOR for NiO-Ru/RuO2@POV suggested higher electrocatalytic activity with a low kinetic barrier. Under the electrocatalytic conditions, the activity of NiO-Ru/RuO2@POV remained stable for 20,000 s. The linear correlation between the current density and the square root of the scan rate signified a diffusion-controlled MOR process. The mechanism of the electrocatalytic oxidation of methanol (CH3OH) with NiO-Ru/RuO2@POV was studied through FTIR and Raman analysis. From the FTIR analysis, it was evident that the oxidation process proceeded through the formation of intermediates like HCHO and HCOOH, while from the Raman study, it was concluded that the Ni and Ru centers participated more strongly in the MOR process.