Breaking Liquid‐Phase Barriers: Concentrated Photothermal Evaporation‐Vapor Splitting at the Gas‐Liquid Interface

ABSTRACT Photocatalytic water splitting is a promising strategy for sustainable hydrogen production, but its efficiency is severely limited by inefficient solar utilization, sluggish charge carrier dynamics, and poor mass transfer in conventional solid‐liquid‐gas triphase systems. Herein, we develop a floating gas‐solid biphasic system that synergistically addresses these bottlenecks by integrating photothermal conversion and photocatalysis at the gas‐liquid interface. Carbonized wood (CW) serves as both a solar evaporator for full‐spectrum solar harvesting and a floating substrate, enabling efficient liquid‐to‐vapor conversion. A Ti‐defective TiO 2 (TO) photocatalyst anchored with highly dispersed Cu atoms (CT) is deposited on CW, where Cu atom anchoring significantly enhances charge carrier separation/transfer efficiency. Under concentrated solar irradiation, the optimal 0.3CT/CW system achieves a remarkable hydrogen evolution rate of 80.09 µmol h −1 , which is 5.14 times higher than that of the traditional triphase powder system. Theoretical calculations confirm that the vapor‐phase environment reduces the reaction energy barrier, while numerical simulations reveal that H 2 diffusion in the gas phase is four orders of magnitude faster than in the liquid phase. Moreover, the system exhibits excellent stability and adaptability to natural water sources. This work offers new insights into the design of high‐efficiency solar energy conversion systems for sustainable hydrogen production.