Two-in-one integrated system—Solar energy activated interfacial collaborative conversions of photo-chemical and photothermal coupling reactions

Abstract

Implementing solar energy-driven photochemical-photothermal coupling conversions represents an efficient strategy to overcome the limitations of single-function solar systems. In this paper, a two-in-one interfacial integrated system is constructed through in situ encapsulation of 3DOM-TiO₂/Cu₂SnS₃ composite within a polyvinylidene fluoride (PVDF) membrane. The integrated system exhibits strong broadband sunlight absorption across the UV–Vis-NIR spectrum, enabled by the narrow band gap of Cu₂SnS₃ and the three-dimensional ordered macroporous (3DOM) structure of TiO₂. This synergy delivers excellent photothermal conversion performance, accelerating interfacial water evaporation to achieve seawater desalination at the liquid-solid interface. Simultaneously, the 3DOM-TiO₂/Cu₂SnS₃ heterostructure facilitates efficient separation of photogenerated charge carriers. The holes oxidize interfacial water vapor to release protons, while the electrons reduce CO₂ with protons to CO, thereby enabling photocatalytic CO₂ reduction at the gas-solid interface. Synergistically, this photochemical-photothermal coupling achieves a CO yield of 6.84 μmol‧g⁻¹‧h⁻¹ from CO₂ reduction and an evaporation rate of 0.93 kg‧m⁻²‧h⁻¹ in seawater desalination. Furthermore, the PVDF-supported system demonstrates long-term stability and recyclability, producing no secondary pollution and reducing the reaction cost. This work offers significant potential for co-producing solar fuels and freshwater.