Syntheses of ZnTi-LDH sensitized by tetra (4-carboxyphenyl) porphyrin for accerlating photocatalytic reduction of carbon dioxide

A strategy of covalently combining layered double hydroxides (LDHs) with photosensitizer was designed to construct organic-inorganic heterojunction for prompting photocatalytic reduction of CO2. A series of tetra (4-carboxyphenyl) porphyrin sensitized ZnTi-LDH (TCPP/ZT) were prepared by an in site hydrothermal method to uniformly load the TCPP molecules on the ZnTi-LDH scaffold, on which the incorporation of TCPP not only broadens the light absorption range, but also facilitates separation and migration of the photogenerated charge carriers, thereby leads to enhancement of the photocatalytic activity. Among the TCPP/ZT, 2 ​wt% TCPP on ZT exhibited a superior photocatalytic performance in CO2 and the cumulative output of CH4 and CO in 5 ​h reached 8.65 ​μmol/g and 1.72 ​μmol/g, respectively, which are 2.50 and 1.56 times higher than those on ZnTi-LDH. The XPS spectra, photoelectrochemical tests and density functional theory (DFT) calculations proved the covalently binding TCPP with ZnTi-LDH through the carboxyl group in TCPP and hydroxyl group on ZnTi-LDH to form ester. Meanwhile the photo-induced electrons are transferred from TCPP to ZnTi-LDH. This work attempted and realized to apply tetra(4-carboxyphenyl)porphyrin sensitized ZnTi-LDH as photocatalyst in photocatalytic CO2 reduction.