Abstract
Addition of noble metals and/or their halides certainly improves the visible-light photocatalytic activity of TiO2, but whether this improvement is due to better photoabsorption capacity of the noble metal or enhanced photoelectrical properties of TiO2 itself, is still a subject of debate. Furthermore, the optimized load of noble metal halides at which best photocatalytic activity in TiO2 occurs hasn’t been explained in the literature consistently. Herein, we investigate the change in intrinsic lattice strain of TiO2 at different AgBr loadings which imparts selective optoelectronic properties turning AgBr/TiO2 system into a visible-light photocatalyst. XRD analysis reveals that beyond a maximum strain developed at an optimum AgBr loading level, the grain boundary interface can no longer withstand the increased strain at Ti—Ti, and Ti—O bonds and a chain of thermodynamically governed crystalline phase transformation within TiO2 begins. Faster dye degradation kinetics corroborate the hypothesis that the catalyst possessing maximum lattice strain shows superior photocatalytic properties. Photoelectrochemical studies was used to quantify the rate of charge transfer (kct) and rate of recombination (kr) of photogenerated electrons and holes. These studies revealed that although higher AgBr concentration may increase charge transfer through plasmon resonance but ultimately kr controls the total charge carrier flux that determines the photocatalytic efficicency of TiO2. Our work highlights methods in which the optimum loading of AgBr can be determined and presents fundamental insight into the role of lattice strain in balancing optical and electrical properties of TiO2 for constructing high-performance photocatalysts suitable for visible light application.
Published Version
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