Effect of intervalence charge transfer on photocatalytic performance of cobalt- and vanadium-codoped TiO2 thin films

Chen, Wen-Fan; Koshy, Pramod; Sorrell, Charles Christopher

doi:10.1016/j.ijhydene.2015.09.055

Cited by 48 publications

(41 citation statements)

References 70 publications

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“…While the sol-gel powders crystallized solely as anatase, which is consistent with other reports, 11,12,17 the Pechini powders consisted of mixed anatase and rutile, which, as shown in 10 c axis contraction provides the dominant distortional effect, which has been suggested previously 11 .…”

Section: Figure 3 Shows Xrd Patterns Of Codoped Tio2supporting

confidence: 90%

“…Cr (transition metal) were used as dopants owing to their unfilled f and d shells, respectively, which have the potential to facilitate intervalence charge transfer between dopants and/or between matrix and dopant(s), which may improve photocatalytic performance. [11][12][13] Ce/Cr codoped nanoparticles were prepared at codopant concentrations up to…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO₂ Nanoparticles through Sol–Gel versus Pechini Syntheses

et al. 2018

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Ce/Cr codoped TiO nanoparticles were synthesized using sol-gel and Pechini methods with heat treatment at 400 °C for 4 h. A conventional sol-gel process produced well-crystallized anatase, while Pechini synthesis yielded less-ordered mixed-phase anatase + rutile; this suggests that the latter method enhances Ce solubility and increases chemical homogeneity but destabilizes the TiO lattice. Greater structural disruption from the decomposition of the Pechini precursor formed more open agglomerated morphologies, while the lower levels of structural disruption from pyrolysis of the dried sol-gel precursor resulted in denser agglomerates of lower surface areas. Codoping and associated destabilization of the lattice reduced the binding energies in both powders. Cr formation in sol-gel powders and Cr formation in Pechini powders suggest that these valence changes derive from synergistic electron exchange from intervalence and/or multivalence charge transfer. Since Ce is too large to allow either substitutional or interstitial solid solubility, the concept of integrated solubility is introduced, in which the Ti site and an adjacent interstice are occupied by the large Ce ion. The photocatalytic performance data show that codoping was detrimental owing to the effects of reduced crystallinity from lattice destabilization and surface area. Two regimes of mechanistic behavior are seen, which are attributed to the unsaturated solid solutions at lower codopant levels and supersaturated solid solutions at higher levels. The present work demonstrates that the Pechini method offers a processing technique that is superior to sol-gel because the former facilitates solid solubility and consequent chemical homogeneity.

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Section: Figure 3 Shows Xrd Patterns Of Codoped Tio2supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO₂ Nanoparticles through Sol–Gel versus Pechini Syntheses

et al. 2018

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“…Consequently, the peak shifts indicating valence increases (greater binding energies) and decreases (lower binding energies) provide information on charge transfer effects. In particular, electron transfer and complementary valence shifts between codopants, between dopant and matrix, and between codopants and matrix can be used to support the conclusion of IVCT [11,39] or multivalence [41]. In addition, these data can indicate the presence of direct redox effects, such as…”

Section: Resultsmentioning

confidence: 99%

“…However, there is only a limited amount of work that has been done on TiO 2 codoped with two transition metals [37][38][39], which enhances the capacity to increase charge transfer through intervalence charge transfer [40,41]. Wang et al [37] demonstrated that 0.10 mol% Fe/0.40 mol% Co codoped TiO 2 nanocrystals revealed the highest photoactivity under visible light, which was attributed to the promotion of charge carrier separation and interfacial charge transfer.…”

Section: Introductionmentioning

confidence: 99%

“…Lin et al [38] demonstrated that undoped TiO 2 thin films revealed the best photocatalytic performance relative to Fe/Mn codoped thin films, which was attributed to the increased density of recombination centres and the enhancement of lattice distortion. Chen et al [39] observed that 0.05 mol% Co/0.05 mol% V codoped TiO 2 thin film exhibited the best photocatalytic performance, which was attributed to modification of the band gap and associated semiconducting effects.…”

Section: Introductionmentioning

confidence: 99%

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Intervalence charge transfer and thermodynamic effects on the photocatalytic performance of Fe/Mo single and codoped TiO2 thin films

et al. 2019

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Fe/Mo single doped and codoped TiO 2 thin films were spin coated on polished fused silica substrates and annealed in air at 450 °C for 2 h. The XPS data for the anatase thin films were distinctive in showing that Fe-doping caused Ti 4+ reduction, Mo-doping caused Ti 4+ oxidation, and codoping did not alter the Ti valence. The XPS data also showed that the precursor valences of Fe 3+ and Mo 5+ were reduced upon annealing. Analysis of the potential roles of thermodynamics and intervalence charge transfer (IVCT) demonstrates that the latter drives the equilibria both in solution and during annealing. Photocatalytic performance testing indicated that Fe-doping was slightly deleterious, Mo doping had a consistent positive effect, and codoping exhibited a clear negative trend as a function of doping concentration. These results are interpreted in terms of the effect of IVCT on the matrix valence, dopant valences, and charge carrier trapping. Fe doping exhibited reduced performance because both matrix Ti (4−x)+ and dopant Fe (3−y)+ acted as electron traps. Mo doping exhibited enhanced performance because the matrix Ti (4+x)+ acted as a hole trap and the dopant Mo (5−x)+ and Mo (4−x)+ acted as electron traps, thereby promoting charge separation. Codoping exhibited a clearly detected negative trend on the performance because, while Ti 4+ played no role, Fe (3−y)+ , Mo (5−x)+ , and Mo (4−x)+ all acted as traps for the majority charge carrier electrons.

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Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO₂₋_x‐Based Heterojunctions

Zheng

Mofarah

Cazorla

et al. 2021

Adv Funct Materials

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Critical catalysis studies often lack elucidation of the mechanistic role of defect equilibria in solid solubility and charge compensation. This approach is applied to interpret the physicochemical properties and catalytic performance of a free-standing 2D-3D CeO 2−x scaffold, which is comprised of holey 2D nanosheets, and its heterojunctions with MoO 3−x and RuO 2 . The band gap alignment and structural defects are engineered using density functional theory (DFT) simulations and atomic characterization. Further, the heterojunctions are used in hydrogen evolution reaction (HER) and catalytic ozonation applications, and the impacts of the metal oxide heteroatoms are analyzed. A key outcome is that the principal regulator of the ozonation performance is not oxygen vacancies but the concentration of Ce 3+ and Ce vacancies. Cation vacancy defects are measured to be as high as 8.1 at% for Ru-CeO 2−x . The homogeneous distribution of chemisorbed, Mo-oxide, heterojunction nanoparticles on the CeO 2−x holey nanosheets facilitates intervalence charge transfer, resulting in the dominant effect and resultant ≈50% decrease in overpotential for HER. The heterojunctions are tested for aqueous-catalytic ozonation of salicylic acid, revealing excellent catalytic performance from Mo doping despite the adverse impact of Ce vacancies. The present study highlights the use of defect engineering to leverage experimental and DFT results for band alignment.

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Effect of intervalence charge transfer on photocatalytic performance of cobalt- and vanadium-codoped TiO2 thin films

Cited by 48 publications

References 70 publications

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO₂ Nanoparticles through Sol–Gel versus Pechini Syntheses

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO₂ Nanoparticles through Sol–Gel versus Pechini Syntheses

Intervalence charge transfer and thermodynamic effects on the photocatalytic performance of Fe/Mo single and codoped TiO2 thin films

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO₂₋_x‐Based Heterojunctions

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Effect of intervalence charge transfer on photocatalytic performance of cobalt- and vanadium-codoped TiO2 thin films

Cited by 48 publications

References 70 publications

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO2 Nanoparticles through Sol–Gel versus Pechini Syntheses

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO2 Nanoparticles through Sol–Gel versus Pechini Syntheses

Intervalence charge transfer and thermodynamic effects on the photocatalytic performance of Fe/Mo single and codoped TiO2 thin films

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO2−x‐Based Heterojunctions

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Product

Resources

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Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO₂ Nanoparticles through Sol–Gel versus Pechini Syntheses

Enhancement of Ce/Cr Codopant Solubility and Chemical Homogeneity in TiO₂ Nanoparticles through Sol–Gel versus Pechini Syntheses

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO₂₋_x‐Based Heterojunctions