In situ construction of a Cu/Cu2O/CuO@hydrogel heterojunction catalyst: Efficient removal of cationic organic dyes irrespective of light availability

The development of photocatalysts offers a promising solution for addressing the challenges of energy needs and environmental pollution. Their practical application, however, is often limited by recyclability and reliance on continuous light irradiation. To tackle these issues‌,‌ Cu/Cu 2 O/CuO heterojunctions were in situ synthesized within a sodium alginate/polyvinyl alcohol (SA/PVA) dual-network hydrogel via‌ freeze-thaw cycling and a subsequent thermal treatment.Consequently, the resulting catalyst achieved high removal efficiencies for methylene blue (MB) (∼92% within 60 min) and several other cationic dyes under both visible light and dark conditions, without the addition of chemical oxidants. This light-irrespective mode of operation offers a potential advantage in energy savings compared to conventional photocatalysts that require continuous irradiation. The material also exhibited satisfactory reusability over multiple cycles and can be readily recovered. These attributes make it a promising candidate for the treatment of cationic organic pollutants, particularly in scenarios where light is intermittent or unavailable, and for applications such as nano-antibacterial textiles. Overall, this work presents a facile synthetic route to a hydrogel-based catalyst that combines light-irrespective activity and convenient recovery, offering a viable strategy for advancing catalytic wastewater treatment and sustainable textile manufacturing.