Correlation of Crystal Structures, Electronic Structures, and Photocatalytic Properties in a Series of Ag-based Oxides:  AgAlO₂, AgCrO₂, and Ag₂CrO₄

Three Ag-based oxides, AgAlO₂, AgCrO₂, and Ag₂CrO₄, were prepared by the cation exchange method. Powder X-ray diffraction analysis showed that AgAlO₂ and Ag₂CrO₄ crystallized in orthorhombic structures and AgCrO₂ crystallized in a hexagonal structure. The band gaps of AgAlO₂, AgCrO₂, and Ag₂CrO₄ were estimated to be 2.95, 1.68, and 1.75 eV, respectively. The photooxidation of Methyl Orange and gaseous benzene were performed to test the activities of the three materials. In the two kinds of reactions, the activity orders were both Ag₂CrO₄ > AgAlO₂ > AgCrO₂, and it was found that the novel photocatalyst, Ag₂CrO₄, showed activity in the visible region up to 570 nm. The correlation among crystal structures, electronic structures, and photocatalytic properties in the three Ag-based oxides is discussed in detail.