Photothermal Evaporator with MXene-Regulated Fe3+/Fe2+ Cycling via Ligand-to-Metal Charge Transfer for Solar Desalination and Wastewater Purification.

Abstract

Combining interfacial solar evaporation and advanced oxidation provides a promising approach to ease global energy shortages and water pollution. However, fabricating bifunctional evaporators with excellent photothermal, catalytic and synergistic properties remains a tough technical challenge. In this work, a glass fiber membrane was adopted as the functional substrate to anchor MXene/MIL-101(Fe) composites, thereby constructing a bifunctional evaporator (M/T-GFM) integrating photothermal and catalytic capacities. As a photothermal component, MXene captures solar light and converts light energy into thermal energy to boost peroxymonosulfate (PMS) activation. Meanwhile, MXene acts as an electron donor to accelerate the Fe3+/Fe2+ redox cycle within MIL-101(Fe) via ligand-to-metal charge transfer (LMCT). It takes merely 20 min to degrade high-concentration Reactive Blue 19 (R.B.19) of 100 mg L-1 completely and 84.32% of phenol in the condensed water, while the water evaporation rate hits 2.49 kg m-2 h-1. Meanwhile, it exhibits excellent purification on actual dyeing and finishing wastewater. Density Functional Theory (DFT) calculations clarify PMS activation over Fe-O-Ti and Fe-O sites. Relying on the synergistic mechanism where MXene-mediated photothermal conversion and LMCT accelerate the Fe3+/Fe2+ redox cycle, this study provides a new strategy for concurrent freshwater generation and wastewater remediation combining interfacial evaporation and a PMS based advanced oxidation process.