Construction of a carbon dots-based Z-scheme photocatalytic electrode with enhanced visible-light-driven activity for Cr(VI) reduction and carbamazepine degradation in different reaction systems

Photocatalytic electrode materials commonly exhibit limited degradation of organic pollutants and toxic metal reduction owing to the low separation efficiency of the electron-hole pair. To enhance the photocatalytic activity, a visible-light-driven Z-scheme TiO2-carbon dots-polyaniline (PANI) photocatalytic electrode was fabricated. After co-decorating with carbon dots and PANI, the light adsorption capability was improved, the bandgap was narrowed by 0.4 eV, the photocurrent density increased by 18.8 times under visible-light excitation and 9.5 times at a bias of 0.95 VRHE, resulting in good simultaneous carbamazepine degradation (44.67%) and Cr(VI) reduction (11.94%) performance. Three photoelectrochemical (PEC) systems were then constructed to further strengthen the water purification performance of the photocatalytic electrode. The simultaneous carbamazepine degradation and Cr(VI) reduction performances were further enhanced to 77.63%-83.29% and 23.70%-25.68%, respectively. The good carbamazepine degradation was attributed to the radical process (center dot OH, 78.63%). Dehydration, hydrolysis, deaminisation, de-ketonisation, and ring-opened reactions were directly responsible for the decomposition and mineralization of CBZ.