Enhancing photocathodic protection performance by controlled synthesis of Bi/BiOBr/TiO2 NTAs Z-scheme heterojunction films

A novel method for the synthesis of bismuth (Bi) nanospheres on the surface of BiOBr/TiO2 nanocomposites is presented, which can be used for controllable preparation of BiOBr/TiO2 and Bi/BiOBr/TiO2 heterojunction films. The synthesis temperature of the one-pot glycol-assisted solvothermal method is the key factor affecting the formation of Bi nanospheres and the loading of BiOBr nanosheets. The structural and optical properties of the films were characterized, and the photocathodic protection property of the prepared photoanodes under different solvothermal temperatures was systematically investigated. The reason for enhancing the photocathodic protection performance of Bi/BiOBr/TiO2 photoanode by introducing Bi nanospheres was also explained, and it was found that the photoanode prepared at 160 °C has the best performance. Under visible light illumination, the Bi/BiOBr/TiO2 photoanode can negatively shift the potential of coupled 316 L stainless steel to ‐430 mV (vs. SCE). The durability tests demonstrated the excellent photochemical stability and good scouring resistance of the Bi/BiOBr/TiO2 photoanode. Moreover, a charge transfer mechanism for Z-scheme heterojunctions was proposed based on the electron spin resonance characterization results of the Bi/BiOBr/TiO2 photoanode. The formation of Z-scheme heterojunctions is mainly attributed to that the Bi nanospheres play a "bridge" role between BiOBr and TiO2, which realizes the Z-scheme electron transport mechanism in the Bi/BiOBr/TiO2 films.