Effect of Porous Layer Thickness on Photocatalytic Performance of Ti/TiO2 Photoanodes Fabricated by Laser Cladding-electrochemical Dealloying
Bulk TiO2 photoanodes suffer from low specific surface area and rapid recombination of photogenerated electron-hole pairs, limiting practical photocatalytic efficiency. This study systematically investigates the quantitative relationship between nanoporous layer thickness and photoelectrochemical performance of Ti/TiO2 photoanodes fabricated via a two-step laser cladding-electrochemical dealloying route. Cu67Ti33 precursor coatings were deposited on pure Ti substrates by laser cladding, followed by selective dealloying in 20 wt.% HNO3 for durations of 1 to 40 h. This process yielded a controllable porous layer thickness ranging from 0 to 260.8 μm. The sample dealloyed for 8 h (npT-8h) exhibited optimal performance: a photocurrent density of 4.54 μA/cm2, charge transfer resistance of 47.28 Ω·cm2, double-layer capacitance of 5.53 mF/cm2, and a methyl orange degradation rate constant of 0.00529 min−1, achieving 61% degradation within 180 min. The enhanced performance is attributed to a synergistic balance between charge separation/transport efficiency and surface reactive site density at the optimal thickness, with auxiliary light-trapping effects from the three-dimensional hierarchical porous network. This work establishes porous layer thickness as an independent, critical parameter for optimizing nanoporous Ti/TiO2 photoanodes, providing a theoretical and experimental framework for high-performance photoelectrode design.