Band regulation of bimetallic MOFs/spaced TiO2 nanotube array heterojunctions and mechanism research on the enhancement of photoelectrochemical cathodic protection

Bimetallic metal–organic frameworks offer exceptional advantages, including high specific surface area, excellent chemical stability, and tunable bandgap characteristics. In this study, a novel bimetallic metal–organic framework/TiO 2 composite photoanode was successfully prepared via a hydrothermal method. The composite exhibited an open-circuit potential negatively shifted to −0.4 V and a photocurrent density of 16.3 μA·cm⁻². The photoanode demonstrated remarkable long-term cathodic protection, effectively safeguarding 304 stainless steel for 28 days in saline environments. By precisely tuning the molar ratio of the two metal centers, the band structure of the bimetallic metal–organic framework was systematically modulated. Notably, at a 1:1 metal ion ratio, the conduction band reached its most negative position, and the work function was minimized. Density-of-states calculations revealed that variations in metal atom proportions altered the electronic configuration, thereby influencing the band structure. Additionally, in situ illuminated XPS was employed to elucidate interfacial charge-transfer dynamics and the photoelectrochemical protection mechanism at the heterojunction interface.