The Interfacial Optimized Engineering and Mechanism of Coupled Photothermal-catalytic Reaction System for Water Treatment

Abstract

Water scarcity and environmental pollution are major challenges that hinder the sustainable development of human society and threaten ecological security and public health. There is urgent demand to develop low-carbon and highly efficient technologies for water pollution control and resource recovery to address above challenges. Among various approaches, solar-driven photothermal and photocatalytic water treatment technologies have shown great potential because of green and efficient characteristics. However, the interfacial design is usually ignored in current photothermal-photocatalytic systems research. Thus, the systems are facing challenges of instability, insufficient reactivity and component incoordination during the practical application. To address these issues, this thesis focused on interfacial optimization strategies for photothermal-photocatalytic systems and their applications in water treatment, designed and constructed photo-reaction system with high stability, sufficient reactivity and component coordination. The underlying regulation mechanisms were systematically elucidated, and the practical feasibility of the systems was further explored. The main research contents and conclusions are summarized as follows:
1. Dense and stable photothermal layer for anti-wetting membrane distillation systems. To solve membrane wetting in solar membrane distillation, this study selected graphene oxide (GO) and thiourea (TU) to construct layer with integration of compactness and photothermal activity. TU crosslinking protected dense structure of GO layer from swelling, enabling to reject surfactant via size sieving effect and realize wetting resistant. And the TU reduction effect further improved the photothermal conversion efficiency of GO layer. On this basis, the wastewater treatment performance of as-prepared membrane was systematically evaluated, which achieved vapor flux of 0.94 kg/m2·h in solar membrane distillation process and resisted wetting more than 72 hours. This study demonstrates the feasibility of dense photothermal strategy in solar membrane distillation systems, and provided new design ideas and methods for anti-wetting and novel composite membranes.
2. Binder-free immobilization of photocatalyst for enhanced system reactivity. To enhance the photocatalytic reactivity of system, this study proposed a novel binder-free immobilization strategy to prepare photothermal-catalytic membranes. The polymer substrate and fibers state was dynamically regulated by organic solvents, and photo-active materials particles could be firmly bound on membrane surface without binder, which broke through the “reactivity-stability” tradeoff in traditional catalytic membrane. Besides, the performance of photocatalytic membrane was investigated. Specifically, the H2O2 production of surface bounding membrane was improved 4.4 times than traditional membrane, and remained stable performance over 20 continuous cycle tests. The VOCs was completely removed by as-prepared membrane during solar vapor generation process. Besides the preparation cost of the membrane was reduced around 39 % comparing to traditional methods. This study lays a key foundation for promoting application of photocatalytic technology in sustainable water purification and provides valuable insights for improving the design of various catalytic membranes.
3. Construction of Janus-structured photothermal-photocatalytic systems for wastewater valorization. To coordinate multi-components in the coupled system and eliminate influence of pollutants on the catalyst activity, this study designed and constructed Janus-structured photothermal-catalytic tris-phase reactor (TPPRS). In TPPRS, the stratified design of photothermal-photocatalytic layers reduced mutual influence between multi-components, and realized orderly solar energy utilization for coupled system. Meanwhile, the Janus structure with hydrophobic top and hydrophilic bottom can effectively protect the catalyst from pollutant interference. Thus, TPPRS treated various water sources and produced clean H2O2 solutions (the yield of 710 μmol/m2), achieving wastewater resourcezation. Besides, TPPRS also presented excellent performance in VOCs removal and disinfection for potable water production. This study provides a feasible idea and implementation path for the efficient and stable operation of photothermal-photocatalytic reaction systems in actual water treatment.
In summary, this thesis proposed interfacial optimization strategies for constructing photothermal-photocatalytic systems with high stability, reactivity and coordination, and deeply elucidated underlying mechanisms. The mentioned systems also presented excellent performance and practical feasibility when in water treatment. This thesis provided solid foundation for the development of photothermal-photocatalytic water treatment materials and technologies, and significantly advance the practical application of solar-driven environmental remediation strategies.

Date of Award	24 Nov 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Wenwei Li (External Supervisor), Kyoung Jin Alicia AN (External Co-Supervisor) & Jin SHANG (Supervisor)