Fig. 2

Catalytic reduction of V⁴⁺ to V^3.5+. a Ultraviolet–visible (UV–Vis) spectra of the reactant electrolyte at different reaction times at 50 °C (inset: color changes of the reactant with the catalytic reaction). b Plots of the conversion with Pt/C at various reaction temperatures and that without Pt/C at 80 °C (100% conversion corresponds to the vanadium oxidation state of +3.5). c TOF (turnover frequency, mmol of V³⁺ (g of Pt)⁻¹ min⁻¹) of the catalytic reaction at different reaction temperatures