Fabrication of heterostructured UIO-66-NH2 /CNTs with enhanced activity and selectivity over photocatalytic CO2 reduction

Developing photocatalysts with superior efficiency and selectivity is an important issue for photocatalytic converting CO2. Hierarchically heterostructured one-dimensional nanomaterials represent a kind of promising catalysts for photocatalytic CO2 reduction on account of the high surface area and synthetic effect between different components. Herein, we synthesized UIO-66-NH2/carbon nanotubes (CNTs) heterostructures via a hydrothermal method, and investigated their photocatalytic performance. The element mapping, X-ray diffraction, and X-ray photoelectron spectroscopy collectively confirmed that the UIO-66-NH2 was successfully loaded on the surface of the CNTs. The specific surface area of the UIO-66-NH2/CNTs is 1.5 times higher than that of UIO-66-NH2. The photocurrent and electrochemical impedance spectroscopy measurements showed that the CNTs could enhance the electron mobility and reduce the recombination of photogenerated electron-hole pairs, which was also confirmed by the Photoluminescence spectroscopy (PL). The CNTs can improve the conductivity of composites and the dispersion of UIO-66-NH2, exposing more active sites, therefore the UIO-66-NH2 can increase the absorption of carbon dioxide and thus enhance the selectivity. The composites remarkably promoted the separation and transition of electrons and thus improved the photocatalytic efficiency of CO2 reduction. More importantly, it was found that the as-prepared composites suppress the hydrogen generation reaction during the CO2 reduction process.