Band‐gap Engineering of Photocatalysts: Surface Modification versus Doping

Kowalska, Ewa; Wei, Zhishun; Janczarek, Marcin

doi:10.1002/9783527808175.ch16

Cited by 13 publications

(12 citation statements)

References 140 publications

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“…410–420 nm for silver- and platinum-modified samples and at ca. 530–560 nm for gold-modified samples, corresponding well with the literature data for spherical NM NPs of 5–30 nm [48,49,50,51,52,53]. The maximum of LSPR slightly differed between samples, e.g., 530, 534, 545, 546 and 561 nm for gold-modified TNW, ST01, FP-6, OAP and TIO10, respectively, suggesting that the smallest gold NPs were deposited on TNW, whereas the largest on TIO10.…”

Section: Resultssupporting

confidence: 86%

“…Accordingly, many methods of titania modification have been proposed to improve its photocatalytic performance, e.g., doping [39,40,41], surface modification [42,43,44] and coupling with other materials (heterojunctions [6,45,46,47,48]). Some reviews on titania modification and doping discussing advantages and disadvantages of various methods might be found here [39,49,50,51,52,53,54,55]. Moreover, preparation of highly crystalline polyhedral TiO 2 particles with crystal facets in definite orientations has been proposed as promising strategy to retard charge carriers’ recombination [56,57,58].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles

et al. 2019

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Octahedral anatase particles (OAP) with eight exposed and thermodynamically most stable (101) facets were prepared by an ultrasonication-hydrothermal (US-HT) reaction from potassium titanate nanowires (TNW). The precursor (TNW) and the product (OAP) of US-HT reaction were modified with nanoparticles of noble metals (Au, Ag or Pt) by photodeposition. Samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), scanning transmission electron microscopy (STEM) and time-resolved microwave conductivity (TRMC). The photocatalytic activity was investigated in three reaction systems, i.e., anaerobic dehydrogenation of methanol and oxidative decomposition of acetic acid under UV/vis irradiation, and oxidation of 2-propanol under vis irradiation. It was found that hydrogen liberation correlated with work function of metals, and thus the most active were platinum-modified samples. Photocatalytic activities of bare and modified OAP samples were much higher than those of TNW samples, probably due to anatase presence, higher crystallinity and electron mobility in faceted NPs. Interestingly, noble metals showed different influence on the activity depending on the semiconductor support, i.e., gold-modified TNW and platinum-modified OAP exhibited the highest activity for acetic acid decomposition, whereas silver- and gold-modified samples were the most active under vis irradiation, respectively. It is proposed that the form of noble metal (metallic vs. oxidized) as well as the morphology (well-organized vs. uncontrolled) have a critical effect on the overall photocatalytic performance. TRMC analysis confirmed that fast electron transfer to noble metal is a key factor for UV activity. It is proposed that the efficiency of plasmonic photocatalysis (under vis irradiation) depends on the oxidation form of metal (zero-valent preferable), photoabsorption properties (broad localized surface plasmon resonance (LSPR)), kind of metal (silver) and counteraction of “hot” electrons back transfer to noble metal NPs (by controlled morphology and high crystallinity).

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Section: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles

et al. 2019

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“…The semiconductor E g defines the minimum frequency of photons required to excite an electron from the valence band to the conduction band, the critical primary event required for photocatalysis to occur. The band structure can be engineered by controlling the polymorphism, morphology, and size (e.g., TiO 2 nanoparticles) or by introducing impurities into the crystal lattice, otherwise known as doping [44,[84][85][86]. Semiconductor doping adds additional filled or vacant quantum states to the band structure that lie within the band gap, reducing the E g and typically resulting in a bathochromic shift in absorption.…”

Section: Inorganic Semiconductor Photocatalysismentioning

confidence: 99%

Heterogeneous photocatalysis in flow chemical reactors

Thomson

Lee

Vilela

2020

Beilstein J. Org. Chem.

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The synergy between photocatalysis and continuous flow chemical reactors has shifted the paradigms of photochemistry, opening new avenues of research with safer and scalable processes that can be readily implemented in academia and industry. Current state-of-the-art photocatalysts are homogeneous transition metal complexes that have favourable photophysical properties, wide electrochemical redox potentials, and photostability. However, these photocatalysts present serious drawbacks, such as toxicity, limited availability, and the overall cost of rare transition metal elements. This reduces their long-term viability, especially at an industrial scale. Heterogeneous photocatalysts (HPCats) are an attractive alternative, as the requirement for the separation and purification is largely removed, but typically at the cost of efficiency. Flow chemical reactors can, to a large extent, mitigate the loss in efficiency through reactor designs that enhance mass transport and irradiation. Herein, we review some important developments of heterogeneous photocatalytic materials and their application in flow reactors for sustainable organic synthesis. Further, the application of continuous flow heterogeneous photocatalysis in environmental remediation is briefly discussed to present some interesting reactor designs that could be implemented to enhance organic synthesis.

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“…One of the main strategies to improve the performance of titania is its coupling with other semiconductors [12]. It is considered that the heterojunction of titania (n-type semiconductor) and p-type semiconducting material should result in an efficient charge separation, and thus, an increase in the lifetime of charge carriers [13].…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic and Antimicrobial Properties of Ag2O/TiO2 Heterojunction

et al. 2019

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Ag2O/TiO2 heterojunctions were prepared by a simple method, i.e., the grinding of argentous oxide with six different titania photocatalysts. The physicochemical properties of the obtained photocatalysts were characterized by diffuse-reflectance spectroscopy (DRS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy (STEM) with an energy dispersive X-ray spectroscopy (EDS). The photocatalytic activity was investigated for the oxidative decomposition of acetic acid and methanol dehydrogenation under UV/vis irradiation and for the oxidative decomposition of phenol and 2-propanol under vis irradiation. Antimicrobial properties were tested for bacteria (Escherichia coli) and fungi (Candida albicans and Penicillium chrysogenum) under UV and vis irradiation and in the dark. Enhanced activity was observed under UV/vis (with synergism for fine anatase-containing samples) and vis irradiation for almost all samples. This suggests a hindered recombination of charge carriers by p-n heterojunction or Z-scheme mechanisms under UV irradiation and photo-excited electron transfer from Ag2O to TiO2 under vis irradiation. Improved antimicrobial properties were achieved, especially under vis irradiation, probably due to electrostatic attractions between the negative surface of microorganisms and the positively charged Ag2O.

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Band‐gap Engineering of Photocatalysts: Surface Modification versus Doping

Cited by 13 publications

References 140 publications

Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles

Influence of Semiconductor Morphology on Photocatalytic Activity of Plasmonic Photocatalysts: Titanate Nanowires and Octahedral Anatase Nanoparticles

Heterogeneous photocatalysis in flow chemical reactors

Photocatalytic and Antimicrobial Properties of Ag2O/TiO2 Heterojunction

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