Unveiling the Cationic Promotion Effect of H₂O₂ Electrosynthesis Activity of O-Doped Carbons

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.

Discriminating active sites for the electrochemical synthesis of H2O2 by molecular functionalisation of carbon nanotubes

“…The higher ORR activity of AQ-CNT-2 possibly results from its higher PZC value, because a more negative surface charge is advantageous for a higher cation population at the catalyst interface during the ORR, and this higher cation population results in higher activity. 28 Notably, the 2e − ORR is unlikely to be mediated by the redox reaction of the AQ moieties because: (i) there are significant differences between the ORR onset potentials and the redox potentials of the catalysts and (ii) the AQ/CNT showed decreased redox signals, yet exhibited good 2e − ORR activity (ESI Fig. S6 † and Fig.…”

“…[20][21][22][23][24][25][26][27][28][29][30][31][32] O-doped carbon materials are generally synthesized via a topdown approach, wherein oxygen functional groups are implanted in as-prepared carbon materials by oxidative treatments, such as HNO 3 , plasma, and heat treatments. [20][21][22][23][24][25][26][27][28] In contrast, the bottom-up approach involves the transformation of O-and C-containing precursors via pyrolysis at high temperatures, which results in graphitised carbon materials with oxygen functionalities. [29][30][31][32] Exploration and optimization of…”

Enhanced Catalytic Performance in Two-Electron Oxygen Reduction Reaction via ZnSnO3 Perovskite

“…Except for the ECSA, the number of active sites on the surface significantly affects the catalytic behavior of materials. Corrected mass activity ( j k ) of these catalysts is then engaged in estimating their H 2 O 2 production in the 2e-ORR process to deeply study the influence of the number of active sites in different catalysts . Among these four catalysts, ZnSnO 3 displays the highest mass activity in the applied potentials, while the Pt/C catalyst shows the lowest mass activity for the 2e-ORR (ZnSnO 3 > ZnO > SnO 2 > Pt/C; Figure a).…”

“…Corrected mass activity (j k ) of these catalysts is then engaged in estimating their H 2 O 2 production in the 2e-ORR process to deeply study the influence of the number of active sites in different catalysts. 43 Among these four catalysts, ZnSnO 3 displays the highest mass activity in the applied potentials, while the Pt/C catalyst shows the lowest mass activity for the 2e-ORR (ZnSnO 3 > ZnO > SnO 2 > Pt/C; Figure 5a). When the potential is set as 0.60 V (Figure 5b), the mass activity of ZnO and SnO 2 catalysts is 478 mA•g −1 and 227 mA•g −1 .…”

Fluorine dopants in tungsten sulfide boost the efficiency of H2O2electro-synthesisviathe oxygen reduction reaction

“…35 In this regard, OOH* species were more susceptible to hydrogenate to form H 2 O 2 . However, in the case of WS 2 , due to the comparatively stronger binding strength with OOH* species, the O–O bond became dissociated; 36,37 thereby, 4e − and 2e − mixed pathways were recorded. As shown in Fig.…”