Polymethylhydrosiloxane-modified gas-diffusion cathode for more efficient and durable H2O2 electrosynthesis in the context of water treatment
Pan Xia, Lele Zhao, Xi Chen, Zhihong Ye, Zhihong Zheng, Qiang He, Ignasi Sirés
Abstract
On-site H2O2 electrosynthesis via two-electron oxygen reduction reaction (ORR) is attracting great interest for water treatment. The use of carbon black-based gas-diffusion electrodes (GDEs) is especially appealing, but their activity, selectivity and long-term stability must be improved. Here, a facile GDEs modification strategy using trace polymethylhydrosiloxane (PMHS) allowed outstanding H2O2 production, outperforming the conventional polytetrafluoroethylene (PTFE)-GDE (1874.8 vs 1087.4 mg L-1 at 360 min). The superhydrophobicity conferred by PMHS endowed the catalytic layer with high faradaic efficiencies (76.2%-89.7%) during long-term operation for 60 h. The electrochemical tests confirmed the high activity and selectivity of the PMHS-modified GDE. Moreover, the efficient degradation of several micropollutants by the electro-Fenton process demonstrated the great potential of the new GDE. An in-depth understanding of the roles of PMHS functional groups is provided from DFT calculations: the −CH3 groups contribute to form a superhydrophobic interface, whereas Si-H and as-formed Si-O-C sites modulate the coordination environment of active carbon centers.