One-Step In Situ Synthesis of a Reduced Graphene Oxide-Based Hybrid Hydrogel for Highly Efficient Water Evaporation and Comprehensive Wastewater Treatment

Solar-driven wastewater treatment via integrated photothermal evaporation and photocatalysis has emerged as a promising approach for freshwater generation, but it is still a challenge in reconciling the fundamental conflict between charge carrier dynamics, where photothermal conversion inherently promotes electron-hole recombination while photocatalytic reactions demand efficient charge separation for optimal performance. Herein, a reduced graphene oxide/MXene-derived TiO2/polyaniline (GMTP) hydrogel is fabricated, which realizes deep integration of photothermal and photocatalytic performance through multistage carrier pathway engineering and redox potential optimization. The well-designed heterojunction between polyaniline and TiO2 induces the thermalization of low-energy carriers through interfacial recombination to induce solar-to-thermal energy conversion, while spatially segregated high-energy carriers with preserved redox potentials initiate cascade reactions involving center dot OH and center dot O2 - for contaminant degradation. Density functional theory and electron paramagnetic resonance have validated that the carrier-selective mechanism achieves coordinated enhancement of photothermal conversion efficiency and catalytic activity through quantum-level carrier modulation. As a result, the GMTP evaporator exhibits a high-water evaporation rate of 2.81 kg m-2 h-1 under 1 sun illumination as well as outstanding degradation efficiencies of more than 99% for various organic contaminants without additional oxidants. This multilevel carrier regulation strategy shows great potential in environmental remediation and the applications of relieving the freshwater crisis.