In:
Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), Vol. 10, No. 20 ( 2022), p. 11298-11305
Abstract:
Halide perovskite materials (HPMs) have been recently employed as photocatalysts in H 2 generation, CO 2 reduction and organic synthesis. However, the high toxicity of lead is directing research towards Pb-free halide perovskites with bismuth as the main candidate to replace Pb. This contribution discloses the synthesis of two bismuth-based halide perovskites with chemical compositions Cs 2 AgBiBr 6 and Cs 3 Bi 2 Br 9 via a solvent-free mechanochemical process in a ball mill. The obtained perovskite powders were characterized via X-ray diffraction, scanning electron microscopy (SEM) and absorption and photoluminescence (PL) steady-state and time-resolved spectroscopy. Cs 2 AgBiBr 6 was able to absorb more in the visible region ( E g = 2.12 eV) as compared to Cs 3 Bi 2 Br 9 ( E g = 2.53 eV). Additionally, PL time decays were considerably longer for Cs 2 AgBiBr 6 ( τ av = 740 ns) with respect to Cs 3 Bi 2 Br 9 ( τ av = 0.3 ns). Both photo-systems were employed in the oxidation of vanillyl alcohol to vanillin, an aldehyde derivative, under UV or visible illumination. Moderate values of photocatalytic conversion (15–30%) were observed except for Cs 2 AgBiBr 6 under visible light irradiation, where 95% conversion could be obtained after only 80 minutes of exposition. PL measurements with the fluorescent probe hydroethidine and electron spin resonance (ESR) demonstrated the formation of superoxide radical species (˙O 2 − ) after photoexcitation, with a larger concentration observed for Cs 2 AgBiBr 6 under visible light due to higher absorption and longer lifetime of the photogenerated charge carriers. Time-resolved PL measurements of both catalysts mixed with vanillyl alcohol powder shed light on the oxidation step upon irradiation taking place due to a hole transfer process from the valence band of the catalysts.
Type of Medium:
Online Resource
ISSN:
2050-7488
,
2050-7496
Language:
English
Publisher:
Royal Society of Chemistry (RSC)
Publication Date:
2022
detail.hit.zdb_id:
2702232-8
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