An effective Z-scheme hybrid photocatalyst based on zinc porphyrin derivative and anatase titanium dioxide microsphere for carbon dioxide reduction

Photocatalysis is considered as one of the most promising technologies to convert carbon dioxide (CO2) into high-valued chemicals. Herein, a novel hybrid photocatalyst for effectively catalyzing CO2 reduction reaction (CO2RR) is synthesized using zinc(II)-tetra-(4-pyridyl) porphyrin (ZnPy4) and MnOx-decorated anatase titanium dioxide (TiO2) microspheres (Mn/AMS) as raw materials. The resultant ZnPy4-Mn/AMS hybrid material exhibits excellent photocatalytic CO2RR performance with methane (CH4)/ carbon monoxide (CO) yields of 44.1/20.9 μmol/(g∙h) and an overall photo-activity of 394.6 μmol/(g∙h), 6.5 times higher than that of anatase TiO2 microsphere (AMS) alone. The effects of ZnPy4/MnOx species on the light absorption, photo-induced charge separation, photo-electrochemical behavior, adsorption/activation capacity of reactants (CO2/H2O) and photocatalytic CO2RR performance of the AMS were studied, and it is found that a direct Z-scheme charge transfer mechanism proceeds in the hybrid material via H-bonding formed between the ZnPy4 and Mn/AMS components to boost the photocatalytic CO2RR activity. These results present an effective strategy for fabricating high-performance artificial photosynthesis for solar-driven CO2 conversion via the hybridization of semiconductor with porphyrin derivative.