Degradation of AO7 through RGO/TiO2 nanotube arrays photoanode in UV/electrical coupling system：performance and mechanism analysis

In order to improve the disadvantage of the high e−-h+ complexation rate in TiO2 NTs. In this study, RGO was deposited on TiO2 NTs using the cyclic deposition method to obtain RGO-TiO2 NTs photoanode. The physical and chemical properties of the photoanodes were analyzed and applied to the photoelectrocatalytic system for treating AO7 dye. The surface structure and composition analysis results indicated that GO was effectively reduced to RGO and uniformly loaded on the surface of TiO2 NTs. The performance studies showed that RGO/TiO2 NTs with 20 cycles exhibited the most favorable optical and photoelectrochemical properties. The forbidden bandwidth of the modified photoanode was reduced from 3.18 to 2.94 eV. Under the synergistic effect of 1.5 V bias voltage and UV light, the photocurrent density of RGO/TiO2 NTs-20 reached 7.46 mA cm−2, which was approximately 1.32 times of that of pure TiO2 NTs. In addition, the photoconversion efficiency of the photoanode increased from 3.14 % to 4.48 % after the modification with RGO. The optimal reaction conditions of the photoelectrocatalytic system with RGO/TiO2 NTs-20 as the photoanode for the treatment of AO7 dyes were electrolyte concentration of 0.1 mol·L−1, pH of 2.7, and stirring speed of 255 r min−1. Under which the degradation rate of AO7 reached 92.97 %, and the rate constant reached 0.01512 min−1. The primary active species involved in the degradation system were h+ and ·OH, with ·O2− serving as the secondary active substance. In summary, RGO can be used as an electron conductor to improve the performance of TiO2 NTs, and the photoelectrocatalytic system with RGO/TiO2 NTs as the photoanode can effectively treat AO7 dyes. The study offers new ideas for preparing efficient photoelectrodes and applying them in the field of pollutant degradation.