Construction of Multifunctional Photothermal/Photocatalytic Materials Based on the Principle of Three Primary Colors: A Case Study of g‐C₃N₄/Ag₂CrO₄

ABSTRACT The strategic design and synthesis of photothermal/photocatalytic materials are pivotal to realizing photothermal conversion water evaporation coupled with photocatalytic sewage purification functions. In this work, based on the principle of three primary colors, brick‐red g‐C₃N₄/Ag₂CrO₄ composite was loaded onto a green polyurethane (PU) sponge using polyvinyl alcohol (PVA) as the linking agent. The resultant PU/PVA/g‐C₃N₄/Ag₂CrO₄ composite exhibits outstanding performance in simultaneous photothermal/photocatalytic water evaporation, pollutant degradation, sterilization, and thermoelectric generation. Under 1.0 kW m⁻² irradiation, the water evaporation rate reaches 3.19 kg m⁻² h⁻¹, while a single thermoelectric module generates a maximum thermoelectric output power of 0.25 W m⁻². Concurrently, rhodamine B (RhB) at a concentration of 4.0 × 10⁻⁴ mol L⁻¹ undergoes complete photocatalytic degradation within 40 min. When the light intensity is 2.0 kW m⁻², the evaporation rate soars to 8.52 kg m⁻² h⁻¹, and the thermoelectric power output increases to 1.1 W m⁻². Furthermore, this photothermal/photocatalytic material based on the principle of three primary colors has excellent photothermal/photocatalytic antibacterial activity against Escherichia coli. By abandoning black light‐absorbing materials, more active sites of the photocatalyst can be exposed. The g‐C₃N₄/Ag₂CrO₄ heterojunction accelerates the separation of photogenerated carriers, while the hydrophilic groups in the photothermal/photocatalytic materials reduce the water evaporation enthalpy. This research provides a novel approach for fabricating multi‐function photothermal/photocatalytic materials, which could quicken the development of solution to freshwater and electricity energy shortages as well as environmental pollution issues.