A photo-assisted electrochemical doping method for preparing Na-doped TiO2 with enhanced photocathodic protection performance in simulated seawater

To address the limitations of TiO 2 as promising material that can provide photocathodic protection (PCP) for metals, a novel technique of photo-assisted electrochemical doping (PED) is developed to prepare Na-doped TiO 2 . Introducing light irradiation during electrochemical doping at an appropriate voltage leads to higher incorporation of sodium into TiO 2 , as well as the generation of more oxygen vacancies and Ti 3+ defects. These changes result in a narrower bandgap, enhanced photogenerated electron-hole separation, and faster electron transfer, ultimately improving the PCP performance of the materials. The mechanism of PED has been analyzed. The Na-doped TiO 2 prepared via PED at the optimal voltage of -1.4 V vs. SCE exhibits a photocurrent density of 180 µA/cm 2 and an open-circuit potential of -0.408 V when coupled with 316 stainless steel (316 SS) in simulated seawater without a hole scavenger. These values provide more effective cathodic protection for 316 SS than those obtained with pristine TiO 2 or with Na-doped TiO 2 prepared via conventional electrochemical doping in the absence of light. This work offers a facile and effective strategy to improve the doping reaction efficiency for preparing Na-doped TiO 2 through electrochemistry method.