Study on a tri-functional photothermal catalytic type air-water composite wall: materials, experimental and running mode analysis

Traditional Trombe walls suffer from functional limitations and seasonal inefficiencies, notably summer overheating. In this study, a tri-functional photothermal catalytic type air-water composite wall system was developed and evaluated. The system aims to simultaneously achieve building energy conservation (heating/hot water) and efficient formaldehyde purification by combining an efficient infrared light-driven catalyst (Mn7Co3Ce1Ox) with an innovative air-water dual working mode. A comprehensive evaluation system combining thermal exergy efficiency and a novel purification exergy efficiency was proposed, along with the establishment of dynamic heat/mass transfer models and a three-factor kinetic model. Experimental and numerical analyses demonstrate that the dual working fluid mode achieves an average air temperature rise of 7.5 °C, hot water temperature increase of 37 °C, and formaldehyde purification efficiency of 68.6 %, with a thermal efficiency of 47.2 %. The single working fluid mode attains a 13.6 °C air temperature rise and 59.8 % purification efficiency. A dynamic thermal/mass transfer model and a three-factor kinetic model reveal that photothermal synergy reduces formaldehyde oxidation activation energy by 36–54 %. The concept of purification exergy quantifies the synergy between energy harvesting and pollutant degradation, yielding a comprehensive exergy efficiency of 0.845 % for dual working fluid operation. This work breaks the functional boundaries of conventional solar walls, offering a paradigm for carbon-neutral buildings through synergetic energy IAQ optimization.