A Sulfonated Porphyrin Polymer/P25m Composite for Highly Selective Photocatalytic Conversion of CO2 into CH4

Highly selective photocatalytic conversion of CO2 into valuable hydrocarbon fuel such as CH4 is a promising solution to tackle greenhouse effect and energy shortage. To achieve this goal, more efforts should be made to design well-performed catalysts. In this work, a series of composite photocatalysts were fabricated for CO2 reduction, through hydrothermal mixing of hydroxylated TiO2 (P25m) with sulfonated covalent porphyrin polymers (s-COP-P). Notably, the optimal sample 2%-s-COP-P/P25m (2% denotes the weight percent of s-COP-P) exhibits the highest production rate (15.5 mu mol g(-1) h(-1)) and selectivity (> 90%) of all composites for the formation of CH4 within 1 h, which are nearly 33 and 2 times as large as that of P25m. This good performance was attributed to improved photogenerated carrier separation efficiency verified by enhanced photocurrent and reduced fluorescence intensity that associating closely with the interaction between two moieties of the composites. Based on energy band structure analyses and hydroxyl radical probing, the reduction of CO2 into CH4 was proposed occurring mainly on P25m moiety companied with the oxidation of H2O into hydroxyl radical. In addition, high cyclic stability was confirmed for the composite catalyst by constant photocatalytic performance lasting over four times of cyclic test. This work provides a facile and effective way to design stable photocatalyst for the conversion of CO2 into CH4 in high production rate and selectivity. [GRAPHICS] .

Automated summary

This study achieved high efficiency and selectivity in the photocatalytic conversion of CO2 into CH4 by fabricating a series of composite photocatalysts. The optimal sample, 2%-s-COP-P/P25m, demonstrated significantly higher production rate and selectivity compared to P25m. This excellent performance was attributed to improved photogenerated carrier separation efficiency and the interaction between the two moieties of the composites.