Fig. 3. Performance and mechanism of Ni SACs/N-C for electrocatalytic NO oxidation.

a Cyclic voltammograms obtained at glassy carbon electrodes modified with Ni SACs/N-C (red curve), Ni NPs/N-C (blue curve) or N-C (green curve) in deaerated phosphate⁻buffered solution (PBS) containing 0.18 mM NO. Black curve represents a control experiment of Ni SACs/N-C in deaerated PBS without NO. b Data are represented as current response recorded with three different modified electrodes shown in (a). Error bars=standard deviation (n = 3). c The proposed structures for electrocatalytic oxidation process of NO on Ni SACs/N-C. d The Gibbs free energy profile along the pathway from NO to HNO₂.