Layered double hydroxide modified TiO2 photoanode for photogenerated cathodic protection of nickel-plated Mg alloy

ZnAl-LDH was deposited on TiO 2 nanotube to form a composite heterojunction. • The heterojunction facilitates the transfer of electrons to the Mg/Ni couple. • The composite shows low potential and high current compared to undoped TiO 2 . • The heterojunction effectively delays the galvanic corrosion of the Mg/Ni couple. To address the intrinsically poor visible-light response of conventional TiO 2 semiconductor and the severe galvanic corrosion of nickel-plated magnesium alloy (Mg/Ni), a ZnAl-layered double hydroxide (ZnAl-LDH)–modified TiO 2 composite photoanode (LDH/TiO 2 ) was rationally designed for photogenerated cathodic protection of Mg/Ni electrode. The in-situ deposition of ZnAl-LDH onto the TiO 2 nanotube arrays constructs a heterointerface that enhances visible-light harvesting and promotes the separation and directional transport of photogenerated charge carriers. Under visible-light irradiation, the LDH/TiO 2 photoanode efficiently injects photogenerated electrons into the Mg/Ni alloy, resulting in a pronounced negative shift in the photoinduced potential and thus suppressing galvanic corrosion. Electrochemical analyses reveal that the LDH/TiO 2 composite exhibits a lower photoinduced potential, higher photocurrent density, and reduced interfacial charge-transfer resistance compared with unmodified TiO 2 nanotube photoanodes, confirming the synergistic effect of LDH modification on charge-transfer kinetics and photogenerated cathodic protection efficiency. This study presents a mechanistically guided approach for constructing high-performance photoanodes for the photogenerated cathodic protection of magnesium alloys.