Z-scheme AgBr/β-MnO2 hydrogel enabling synergistic photothermal evaporation and Photocatalysis for efficient volatile organic compounds abatement

A bifunctional evaporator for sola evaporation and photocatalysis was developed. • The 3D hydrogel shows broad-spectrum solar absorption and high energy efficiency. • The Z-scheme heterojunction boosts charge separation and phenol degradation. • A detailed degradation mechanism and reaction pathway of phenol are proposed. Solar interfacial evaporation (SIE) has attracted increasing attention in recent years due to its environmental friendliness, high efficiency, and low-carbon-emission characteristics. However, volatile organic compounds (VOCs) are often not effectively removed during the evaporation process, which can lead to secondary contamination of the collected condensate. Integrating SIE with photocatalysis for seawater desalination has therefore emerged as an effective strategy to mitigate the accumulation of VOCs in the condensate during seawater treatment. In this study, manganese (IV) oxide nanomaterials were coated with silver bromide to construct an AgBr/β-MnO 2 heterojunction that suppresses the fast charge annihilation of photoinduced electron–hole pairs and enhances photocatalytic efficiency. The resulting composite was further incorporated into a photothermal hydrogel (AgBr/β-MnO 2 -PH) matrix with excellent photothermal evaporation properties, forming a three-dimensional (3D) photocatalytic evaporation system capable of significantly improving the removal efficiency of VOCs during photothermal evaporation. Under standard solar irradiation (1 sun, 1 kW m −2 ), the porous acrylamide-based hydrogel evaporator achieved an evaporation rate of 3.47 kg m −2  h −1 and a photothermal transformation efficiency of 93.98%. In-situ irradiated XPS reveals light-induced electron enrichment on AgBr accompanied by electron depletion on β-MnO 2 , providing experimental support for a direct Z -scheme interfacial charge-transfer pathway that promotes carrier separation and reactive oxygen species (ROS)-mediated photocatalysis. Consequently, the AgBr/β-MnO 2 -PH system exhibits a removal efficiency exceeding 99% when treating phenol-containing wastewater. Overall, this work demonstrates an effective strategy for coupling SIE with photocatalytic degradation of VOCs. The developed AgBr/β-MnO 2 -PH provides a promising approach for producing freshwater from VOC-contaminated sources and offers new insights into the application of solar energy in seawater desalination and wastewater purification. Download: Download high-res image (337KB) Download: Download full-size image