γ-PGA-dependent growth of BiOBr nanosheets with exposed {010} facets for enhanced photocatalytic RhB degradation

As an efficient strategy to enhance charge-separation and photocatalytic performance, crystal-facet engineering has inspired a great deal of research interest in recent decades. In this work, a novel gamma-polyglutamic acid (gamma-PGA)mediated hydrothermal strategy is introduced unprecedentedly to transform the exposed facets of single-crystal BiOBr ultrathin nanosheets from {001} to {010}. The facet-dependent photocatalytic performance of samples is systematically evaluated by photodegradation of Rhodamine B (RhB) as model pollutants under light illumination of lambda >= 420 nm. BiOBr with {010} as dominantly exposed facets demonstrates higher photocatalytic activity compared to those with exposure of {001} plane. As evidenced by the electrochemical impedance spectra (EIS), transient photocurrent response (TPR) and photoluminescence (PL) spectra, the enhanced photocatalytic performance is predominantly due to the facilitated charge-separation and decreased charge-recombination of photoexcited electron-hole pairs over the {010} facet of BiOBr. Additionally, photogenerated superoxide radicals (center dot O2-) and holes (h+) are identified as the main reactive species responsible for photodegrading RhB based on the results of radical-trapping and ESR experiments. Overall, the gamma-PGA-mediated hydrothermal approach offers a simple and environmental-friendly method for tailoring the exposed facets of Bi-based oxyhalide photocatalysts to optimize charge-separation and photocatalytic performance.