A solar-driven heterojunction hydrogel with reversible phase transition for efficient photocatalytic decontamination and freshwater generation†

Abstract

Wastewater purification using the commonly used solar-driven hydrogel with phase transition-induced mechanisms is restricted by limited adsorption capacity, a narrow working scope and finite stability. To address these challenges, a heterostructure design is employed, incorporating reduced graphene oxide (RGO) integrated with titanium dioxide (TiO₂) and zinc sulfide (ZnS) to fabricate a heterojunction catalyst (RTZ) that possesses dual capabilities: photocatalysis degradation and photothermal conversion-induced reversible phase transition. The RTZ composite modules have been innovatively incorporated into an LCST-type PDEAAm three-dimensional network structure to create a solar-driven heterojunction hydrogel (PRTZ), which facilitates water purification through photocatalytic degradation and reversible phase transitions. Benefiting from multiple functional components in the hydrogel and numerous polyfunctional groups serving as adsorption and photocatalytic degradation sites within the networks, the hydrogel exhibits excellent antifouling, bactericidal, and purification performance. The PRTZ heterojunction hydrogel demonstrates remarkable performance, achieving over 96.09% contaminant removal efficiency, a water collection rate of 8.87 kg m⁻² h⁻¹ under 0.8 sun irradiation, and 100% antibacterial activity. This novel multi-modal mechanism, which integrates photocatalytic decontamination with phase transition-enabled water release, represents a pioneering approach to sustainably produce clean water and address water pollution.