Unveiling the Cationic Promotion Effect of H<sub>2</sub>O<sub>2</sub> Electrosynthesis Activity of O-Doped Carbons
Juyeon Lee, June Sung Lim, Gyeonghye Yim, Hongje Jang, Sang Hoon Joo, Young Jin
Abstract
H2O2 electrosynthesis is an emerging clean chemical technology, whose efficiency critically depends on the activity and selectivity of electrocatalysts for two-electron oxygen reduction reaction (2e– ORR). Here, we demonstrate that 2e– ORR activity of oxygen-doped carbons, which have been one of the most promising catalysts for this reaction, can be substantially influenced by the types and concentrations of cations in electrolytes. Heat-treated carbon comprising active oxygen functional groups exhibits cation-dependent 2e– ORR activity trends in alkaline media, following the order Cs+ > K+ > Li+. Importantly, an electrolyte with a high cation concentration (0.1 M KOH + 0.5 M KCl) afforded the highest 2e– ORR mass activity (250 ± 30 A gcat–1 at 0.70 V vs reversible hydrogen electrode) ever reported. We have established that the cation promotion effect correlates with cation-dependent electron-transfer kinetics, which regulates the rate-determining first electron transfer to O2.