Hierarchical diffusion pathways into VOC adsorption films by direct ink writing and ammonium carbonate treatment

Abstract

In-situ thermally restorable adsorption films exhibited brilliant performance for indoor volatile organic compounds (VOCs) purification with negligible wind resistance and considerable lifetime. However, the morphology of adsorption films should be restructured for better adsorption kinetics. This study structured adsorption films with submillimeter-sized channels by direct ink writing (DIW). Submicron-micron-sized porous structure was further fabricated through ammonia carbonate treatment. Pore size distribution characterization proved 33% of extra mesopores were created in the hierarchical porous adsorption film. Dynamic adsorption behaviours for formaldehyde and toluene illustrated that the hierarchical porous adsorption film exhibited an over 80% initial one-pass efficiency for both formaldehyde and toluene, improved by 20% over the plane adsorption film. The purification rate was also significantly improved by 83% and 67% for formaldehyde (from 0.059 mg g-1h−1 to 0.106 mg g-1h−1) and toluene (from 0.143 mg g-1h−1 to 0.239 mg g-1h−1), respectively. This study proposed a method for conveniently preparing multi-scale porous structured adsorption components under mild conditions. The hierarchical diffusion pathways induced by DIW and ammonium carbonate treatment will enhance the adsorption kinetics and the purification performance of the adsorption film, overcoming the weak purification performance and short material lifetime of the existing indoor VOCs adsorption components. This research can be further applied to gas separation, as well as gas sensing, as DIW can achieve sub-millimeter scale resolution, providing a versatile approach for heat and mass transfer enhancement in chemical and environmental fields.