Abstract: TiN nanoparticles exhibit significant plasmonic photothermal properties, yet their role within TiN/TiO₂ composite photoanodes remains unclear. In this work, TiN nanoparticles were controllably synthesized via a Sol-Gel method using urea as the nitrogen source. A series of TiN/TiO₂ composite photoanodes were fabricated by adjusting the spin-coating volume of the TiN dispersion. The results show that TiN nanoparticles with size of 10~30 nm can be obtained by controlling the urea/TiCl₄ molar ratio to 8. The TiN/TiO₂ composite photoelectrode, fabricated by spin-coating 200 μL of 2 wt% ethanol dispersion of these nanoparticles, achieves a photocurrent density of 1.47 mA·cm^-2 and an open-circuit photovoltage of 0.69 V under simulated solar illumination, enhanced by 75% and 57%, respectively, compared to pristine TiO₂ photoelectrode, and the electrode maintains stable performance for over 3 h. Introduction of TiN enhances visible light absorption of material. Therefore, under illumination TiN nanoparticles undergo rapid heating, and the generated heat is efficiently transferred to the TiO₂ substrate, promoting interfacial charge transfer and surface reaction kinetics. These findings demonstrate that the photothermal effect of TiN can elevate the local temperature at the photoelectrode surface, thereby enhancing photoelectrochemical water splitting performance.

Key words: TiN nanomaterials, Sol-Gel method, TiN/TiO₂ composite photoanode, photoelectrochemistry, plasmonic photothermal effect