An anion-controlled crystal growth route to Zn2GeO4nanorods for efficient photocatalytic conversion of CO2 into CH4

Abstract

For photoreduction of CO₂ into solar fuels driven by photocatalysis, a means to convert solar energy into chemical energy, a semiconductor photocatalyst with a specific crystal surface and high chemical stability is expected to achieve high activity and selectivity. Here, (110) facets exposed Zn₂GeO₄ nanorods with different aspect ratios were prepared by the ion exchange reaction between Na₂GeO₃ colloidal solution and various zinc salt solutions. The aspect ratio of Zn₂GeO₄ can be adjusted in the wide range from 2.5 : 1 to 20 : 1, depending on the acid radical. In this synthetic route, the Na₂GeO₃ precursor is a strong base, but strong acids such as HCl, HNO₃ and H₂SO₄ as by-products were formed, meaning that the Zn₂GeO₄ single-crystal nanorods have good chemical stability in acid as well as in base. The excellent hydrothermal stability for the Zn₂GeO₄ nanorods in NaOH solution provides a simple method to obtain a hydroxylated surface for high performance in the photocatalytic conversion of CO₂ and H₂O to hydrocarbons fuels.