Synergistic Engineering of La-Doped TiO ₂ with Plasmonic Ag Nanoparticles for Enhanced Photoelectrochemical Water Splitting

To develop high-efficiency photoanode materials for solar-driven photoelectrochemical (PEC) water splitting, we propose a synergistic modification strategy combining rare-earth doping and Ag nanoparticles (NPs) plasmonic effects to boost the visible-light photoelectrochemical performance of TiO2 nanorod arrays (NRAs). Rare-earth (La, Ce, Gd) doping introduces oxygen vacancies and defect levels into TiO2, narrowing its bandgap and promoting carrier separation. The optimal 5%La-doped TiO2 delivers a 6.30-fold photocurrent enhancement relative to pristine TiO2. Subsequent coupling with plasmonic Ag nanoparticles via the localized surface plasmon resonance (LSPR) effect delivers an 11.75-fold further enhancement in photocurrent density relative to the single 5%La-doped TiO2, the best performance of this work. COMSOL finite element simulations and transient fluorescence spectroscopy confirm that LSPR-enhanced local electric fields and optimized Ag-TiO2 interfacial carrier dynamics effectively promote photogenerated carrier separation and migration. This work elucidates the fundamental synergy between plasmonic effects and rare-earth defect engineering, providing systematic theoretical and experimental guidance for the rational design of high-performance TiO2 based photoanodes for efficient PEC water splitting.