Elucidating deactivation mechanisms of Pd-doped and un-doped Ti/SnO2-Sb electrodes

Ti/SnO2-Sb (ATO) is a promising anode for electrochemical oxidation process with low cost and high efficiency, while its application is limited due to the short service life. In this study, Pd-doping increased the service life of ATO electrode by 53 times from 2.8 h to 150 h. To provide a deeper insight, we investigated the deactivation mechanisms of Pd-doped and un-doped ATO electrodes. The changes in electrochemical performance, physical properties and chemical compositions of deactivated ATO electrodes were detailedly characterized using LSV, EIS, ICP, SEM, XRD, FTIR, XPS, EDS and contact angle measurements. Although the dissolution/shedding of coating and formation of tin hydroxide on the surface were two reported deactivation mechanisms of un-doped ATO electrode, the selective dissolution of Sb was found as a new important deactivation mechanism. Pd-doping increased the service life of ATO electrode by effectively suppressing the dissolution of Sb and Sn, and the formation of tin hydroxide through forming a compact coating with enhanced exposed {101} crystal plane and high hydrophobicity. However, Pd-doped ATO electrode was deactivated due to the gradual dissolution of doped Pd atoms resulting in the change of coating structure and the loss of coating protection. (C) 2020 Elsevier B.V. All rights reserved.