Zinc Gallogermanate Solid Solution: A Novel Photocatalyst for Efficiently Converting CO sub(2) into Solar Fuels

• Published in: Advanced functional materials 2013-04, Vol.23 (14), p.1839-1845
• Main Authors: Yan, Shicheng, Wang, Jiajia, Gao, Honglin, Wang, Nanyan, Yu, He, Li, Zhaosheng, Zhou, Yong, Zou, Zhigang
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Converting; Hole mobility; Orbitals; Photocatalysis; Solid solutions; Spinel; Zinc
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201202484

As global energy demand continues to grow, the need to find a carbon-neutral and sustainable energy source for future generations has become imperative. An especially attractive solution is to store solar energy in the form of chemical fuel via artificial photosynthesis to convert carbon dioxide into hydrocarbons. An artificial photosynthesis system is introduced based on a zinc gallogermanate solid solution photocatalyst that can convert the carbon dioxide and water into methane. The solid solution of cubic spinel ZnGa sub(2)O sub(4) and pseudocubic inverse spinel Zn sub(2)GeO sub(4) is successfully synthesized by hydrothermal ion exchange reaction. Introducing Zn sub(2)GeO sub(4) into ZnGa sub(2)O sub(4) can effectively narrow band gap by the upshift of valence band edge from the enhanced p-d (O2p-Zn3d) repulsion effect by incorporating s and p orbitals of Ge, and the downshift of conduction band edge by introducing the low-energy s orbital of Ge. The zinc gallogermanate solid solution has a light-hole effective mass, which is beneficial to improving hole mobility, and thus enhancing the ability of photocatalyst in water oxidation to provide protons for CO sub(2) photoreduction. As a result of band gap narrowing and high hole mobility, the zinc gallogermanate solid solution exhibits high activity in converting CO sub(2) and H sub(2)O into CH sub(4) and O sub(2). A hydrothermal ion-exchange reaction route is used to synthesize a solid solution of cubic spinel ZnGa sub(2)O sub(4) and pseudocubic inverse spinel Zn sub(2)GeO sub(4). Introducing Zn sub(2)GeO sub(4) into ZnGa sub(2)O sub(4) narrows the band gap and induces the light-hole effective mass. As a result of band gap narrowing and high hole mobility, the zinc gallogermanates solid solution exhibits high activity in converting CO sub(2) and H sub(2)O into CH sub(4) and O sub(2).