HZSM-5 zeolites containing impurity iron species for the photocatalytic reduction of CO2 with H2O

Abstract

We report the application of the commercial HZSM-5 zeolite as an efficient and stable photocatalyst for the photoreduction of CO₂ with H₂O at room temperature. CO and H₂ were the main reduction products besides a trace amount of hydrocarbons. The activity of CO evolution was dependent on the source of various zeolites. The highest CO evolution rate over the HZSM-5 samples was 3.32 μmol g⁻¹ h⁻¹ under UV-light irradiation. The control experiments combined with the characterization results of XRD, UV-vis DRS and ESR revealed that the photocatalytic activity was not related to Si/Al ratios or Al–O units but was associated with the content of Fe impurities in the zeolite samples. A reaction mechanism of CO₂ photoreduction on Fe species in zeolites was proposed. [Fe³⁺–O²⁻] species as a photoactive centre can be excited by UV light to form a charge-transfer excited state, [Fe²⁺–O⁻]*, which was responsible for the CO₂ reduction reaction. This work demonstrates zeolite molecular sieves as an efficient photocatalyst for CO₂ conversion and helps us to understand the photocatalytic nature of zeolites.