While temperature fluctuations and chloride (Cl–) ions are inevitable factors in real-world seawater splitting, their coupled influence on photoanode kinetics remains poorly understood. This study explores these complex interfacial dynamics by evaluating TiO2 nanorod arrays, which were identified as the optimal balance between photogenerated carrier transport and electrochemical properties compared to nanochannel and nanoparticle arrays. Leveraging this optimized photoanode in a 0.5 M NaCl electrolyte at 65 °C, we achieved a peak photocurrent of 1.055 mA cm–2, improving performance compared to low-temperature or Cl–-free conditions. Confirmed by X-ray Photoelectron Spectroscopy analysis, Mott–Schottky analysis reveals that Cl– specific adsorption induces band flattening and weakens the built-in electric field, typically a detrimental effect, but it is not the primary driver of performance. Instead, impedance spectroscopy uncovers a dominant surface-mediated mechanism specific to high-temperature saline environments: Cl– specific adsorption creates high-capacitance surface states acting as hole reservoirs. Coupled with thermally accelerated diffusion kinetics, these states facilitate rapid hole consumption to drive a superior photoresponse, effectively overriding the weakened built-in field. However, this enhancement comes at a steep price: the aggressive chloride environment leads to rapid poisoning and deactivation of surface active sites. Consequently, this study cautions against interpreting high current densities solely as catalytic success. This work exposes the danger of corrosion-induced currents being misinterpreted as performance gains, offering a crucial perspective for future studies to carefully re-evaluate apparent efficiency in chloride-mediated water electrolysis.
Li et al. (Wed,) studied this question.