Abstract
Octahedral anatase particles (OAP, with eight equivalent {101} facets) and decahedral anatase particles (DAP, with two additional {001} facets) were modified with nanoparticles of noble metals (Au, Ag, Cu). The titania morphology, expressed by the presence of different arrangements of exposed crystal facets, played a key role in the photocatalytic properties of metal-modified faceted titania. In the UV/vis systems, two-faceted configuration of DAP was more favorable for the reaction efficiency than single-faceted OAP because of an efficient charge separation described by the transfer of electrons to {101} facets and holes to {001} facets. Time-resolved microwave conductivity (TRMC) and reversed double-beam photoacoustic spectroscopy (RDB-PAS) confirmed that distribution of electron traps (ET) and mobility of electrons were key-factors of photocatalytic activity. In contrast, metal-modified OAP samples had higher photocatalytic activity than metal-modified DAP and metal-modified commercial titania samples under visible light irradiation. This indicates that the presence of single type of facets ({101}) is favorable for efficient electron transfer via shallow ET, whereas intrinsic properties of DAP result in fast charge carriers’ recombination when gold is deposited on {101} facets (migration of “hot” electrons: Au→{101}→Au).
Highlights
Fossil energy exhaustion and environmental pollution are major challenges to sustain development of human society
It has been shown that the modification of octahedral anatase particles (OAP) and decahedral anatase particles (DAP) by NMs enhances their photocatalytic performance
The direction of improvement relates to the type of photodeposited metal, faceted titania morphology and selected reaction system
Summary
Fossil energy exhaustion and environmental pollution are major challenges to sustain development of human society. Noble metals (NMs: Pt, Au, Ag, Ir, Pd) in the form of either adsorbed complexes [41] or metallic deposits [42] have been extensively studied for more than forty years as a pool for UV-photogenerated electrons retarding charge carriers’ recombination [43,44,45] Very recently another property of NMs, i.e., visible light (vis) absorption due to plasmon resonance, has been used for activation of wide-bandgap semiconductors toward vis, i.e., mainly titania, and other materials, such as CeO2 [46], Fe2O3 [47], ZnO [48] and KNbO3 [49]. Some data for OAP and DAP have already been published (bare [88,89,90] and NM-modified faceted titania [91,92,93]), in this study, for the first time, NM-modified OAP and DAP have been comparatively analyzed to recognize how the different types of faceted anatase morphology can influence photocatalytic activity of samples modified by NMs in different reaction systems
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