Boosting Photocatalytic Water Vapor Splitting by Nanosecond Infrared Laser-Assisted Synthesis of Photothermal Substrate

Abstract

Solar-driven hydrogen production is considered a promising solution to the current energy crisis and environmental pollution. The efficiency of photocatalytic water splitting for hydrogen production can be improved by constructing an effective biphase photocatalytic system. In this study, laser-ablated wood was used as a photothermal substrate that effectively generates water vapor below the boiling point of water. When integrated with TiO₂ in a photothermal–photocatalytic system, it achieves a hydrogen production rate of 42.4 mmol m^–2 h^–1 under an irradiance of 3 kW m^–2. To obtain a photothermal substrate with high evaporation efficiency, nanosecond infrared (ns IR) laser ablation was employed to treat the surface of the wood, leveraging its strong thermal effects to cleave the C–C bonds in lignin and other polymers. This process resulted in instantaneous selective oxidation to CO, exposing the internal pore structure of the wood. Additionally, laser ablation enhanced the carbonization of the surface of the wood, leading to improved light absorption and water evaporation performance of the ablated wood. FT-IR analysis revealed a strong interaction between the hydroxyl groups on the surface of the laser-ablated wood and TiO₂ through hydrogen bonding, effectively preventing the detachment of the photocatalyst. This solid–gas biphase system, consisting of photocatalyst, water vapor, and hydrogen, exhibits lower reaction resistance and significantly enhances catalytic activity, highlighting its great potential for future applications in solar-driven hydrogen production.