Polymeric Layered Films for TiO₂‐Au/CuS Tandem Photothermal Catalytic H₂ Production in Harsh Seawater and Waste Plastic Media

Abstract Conventional suspension photocatalysts face stability and efficiency challenges in harsh, unconditioned environments characterized by high alkalinity, salinity, and organic species in seawater and wastewater. Moreover, suspension‐based photothermal‐assisted catalysis presents further challenges, particularly concerning formation of heterojunctions between photocatalysts and photothermal materials that disrupt charge‐transfer pathways and are exacerbated by photothermal heating‐induced carrier recombination. Here, a photocatalytic system is proposed in which three key photoprocesses: photothermal, photogeneration‐charge separation, and photoredox are spatially decoupled yet coordinated, aimed at addressing prevalent challenges of photothermal‐assisted catalysis and adsorption‐mediated catalyst deactivation in harsh environments. Essentially, the proposed polymeric tandem photothermal catalytic (PTPC) film consists of TiO 2 /Au photocatalytic and CuS photothermal layers, spatially separated and encapsulated by polymeric layers, which serve as spacer inhibitors to conflicting photochemical‐photothermal pathways and corrosion‐resistant redox medium. The PTPC film exhibits enhanced light absorption, mass transfer, and photothermal effect, surpassing traditional suspension catalysts and enabling interfacial redox reactions on the passive film surface. The PTPC system represents a new paradigm of polymeric film photocatalysis, enabling unimpeded photoredox‐photothermal pathways and catalyst stability for application in hostile seawater and plastic waste environments. Such a paradigm can be used to develop localized, onsite solutions for photothermal H 2 production that minimize logistical and environmental challenges.