Hybrid TiO2-CZTS Photocatalyst for Efficient Conversion of CO2 into Methane under Irradiation

Abstract

Carbon dioxide is a key problem causing global warming. Photocatalytic CO2 conversion into hydrocarbons is one of the effective strategies to solve this issue. Amongst photocatalysts, TiO2 (anatase)-based materials are the most stable and preferred photocatalysts. However along with its good characteristics, TiO2 has a disadvantage of wide bandgap (3.2 eV). For the efficient use of TiO2 photocatalysts, one of the approaches is to couple it with another small bandgap photocatalytic material focused on broadened light absorption region. Cu2ZnSnS4 (CZTS), a well-known p-type semiconductor, is a new type of promising material to fulfill the above requirement. It has a narrow direct band gap of 1.45~1.61 eV and composed of abundant and non-toxic elements. In addition, due to proper bandgap alignment, the hybrid TiO2-Cu2ZnSnS4 (CZTS) can absorb a broader region of light as compared to TiO2 and enhance the photocatalytic conversion of CO2. Furthermore, p-n heterojunction forms in between ptype CZTS and n-type TiO2 and can reduce the electron-hole recombination, contributing to the performance improvement of the hybrid photocatalytic materials for CO2 photoconversion. In this study, an attempt is done to fabricate hybrid photocatalyts based upon p-n heterojunction and applied for CO2 photoreduction. CZTS, a wellknown p-type semiconductor with a narrower direct band gap of 1.5 eV, is synthesized and coupled with n-type TiO2. The synthesis of hybrid photocatalyts is confirmed by numerous characterization techniques such as XRD, TEM, and UV/Vis spectroscopy. The methane production also is measured by using gas chromatogram (GC). Our research provides a novel information for the design of efficient p-n heterojunction structure based nanocomposite photocatalysts. ⓒ 2015 DGIST