Hydrogel‐Based Photothermal‐Catalytic Membrane for Efficient Cogeneration of Freshwater and Hydrogen in Membrane Distillation System

Abstract Photothermal‐catalytic (PTC) process is a promising way to produce freshwater and clean hydrogen by integrating solar‐driven desalination and water splitting. However, efficient solar spectrum utilization coupled with effective mass and thermal management poses key challenges in developing multifunctional PTC systems. Here, a highly stable hydrogel membrane (CdS/MX‐HM) that incorporates MXene and in‐situ generated CdS as the PTC materials into a customized vacuum membrane distillation (VMD) setup is demonstrated. The CdS/MXene composites utilize the full solar spectrum, with MXene contributing to photothermal ability and serving as a co‐catalyst to enhance photocatalytic performance, which are effectively integrated into the membrane system. These functional materials are immobilized within the hydrophilic PVA/chitosan hydrogel layer, which creates a supramolecular network that provides excellent stability and protection while offering an interface for PTC processes. Supported by the hydrophobic PTFE membrane substrate, the integrated system enables fast gas transfer to the permeate, completing the dual‐function design. Through systematic optimization of membrane structure and operational parameters, the PTC‐VMD system achieves a water flux of 1.63 kg m − 2 h − ¹ and a hydrogen production rate of 3099 µmol m − 2 h −1 under one sun irradiation, demonstrating its potential as a sustainable solution for the water‐energy nexus challenge.