Gas-Solid Phase Reaction Derived Silver Bismuth Iodide Rudorffite: Structural Insight and Exploring Photocatalytic Potential of CO2 Reduction

Photocatalytic reduction of CO ₂ is a promising strategy to mitigate the effects of global warming by converting CO ₂ into valuable energy-dense products. Silver bismuth iodide (SBI) is an attractive material owing to its tunable bandgap and favorable band-edge positions for efficient CO ₂ photoreduction. In this study, SBI materials, including AgBi ₂I ₇, AgBiI ₄, Ag ₂BiI ₅, and Ag ₃BiI ₆ are first synthesized, through gas-solid reaction by controlling the stoichiometric ratio of reactants. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) results revealed that the distance between Ag-I is proportional to the degree of Ag ions delocalization, which occupies the vacant sites. That greatly retards the charge recombination at vacant sites. In addition, the surface potential via photo-assisted Kelvin probe force measurements of various SBI catalysts shows that Ag ₃BiI ₆ exhibits the highest surface potential change due to the rich delocalized Ag ions. This results in effective charge carrier transport and prevention of charge recombination at vacant sites. Taking the above advantages, the averaged CO and CH ₄ production rates for Ag ₃BiI ₆ achieved 0.23 and 0.10 µmol g ⁻¹ h ⁻¹, respectively. The findings suggest that Ag ₃BiI ₆ has a high potential as a novel photocatalyst for CO ₂ reduction and sheds light on the possibility of solving environmental contamination and sustainable energy crises.