Solar-driven surface-heating membrane distillation using Ti₃C₂T_x MXene-coated spacers

The emergence of two-dimensional (2D) MXenes as efficient light-to-heat conversion materials offers significant potential for solar-based desalination, particularly in photothermal interfacial evaporation, enabling cost-effective solar-powered membrane distillation (MD). This study investigates solar-powered MD afforded by a photothermally functionalized spacer, which is built by spray-coating Ti₃C₂T_x MXene sheets on metallic spacers. 2D Ti₃C₂T_x MXene gives an ultrahigh photothermal conversion efficiency; thereby, by Ti₃C₂T_x MXene-coated metallic spacer, this rationally designed spacer allows for a localized photothermal conversion and interfacial feed heating effect on the membrane surface, especially for MD operation. As a feed spacer and a photothermal element, Ti₃C₂T_x MXene-coated metallic spacer exhibited stable enhanced water flux of up to 0.36 kg·m⁻²h⁻¹ under one sun illumination for a feed salinity of 35 g·L⁻¹, corresponding energy conversion efficiency of 28.3 %. Overall, the developed photothermal Ti₃C₂T_x MXene-coated spacers displayed great potential in enhancing the performance, scalability, and feasibility of solar-driven MD process, paving the way for further development of photothermal elements that can be implemented in solar MD applications.