Photocatalytic Degradation of Methyl Orange by CeO2 and Fe–doped CeO2 Films under Visible Light Irradiation

Channei, Duangdao; Inceesungvorn, Burapat; Wetchakun, Natda; Ukritnukun, Supphatuch; Nattestad, Andrew; Chen, Jun; Phanichphant, Sukon

doi:10.1038/srep05757

Cited by 397 publications

(166 citation statements)

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“…This would have served to disrupt the boundary layer. However, subsequent work on the same material [74] also reported the retention of photocatalytic activity of thin films of Fe-doped CeO 2 in static methyl orange solution. Consequently, the photocatalysis mechanism appears to operate in both turbulent and static flow conditions.…”

Section: Discussionmentioning

confidence: 92%

“…However, under static liquid conditions [74], a saturated boundary layer of species of the same type as leached from the solid would have been established [37][38][39]. However, reductive dissolution effectively would introduce the relevant Ce 3+ -H 2 O equilibria, again leading to the same hydrated surface layer of precipitated solid CeO 2 ·2H 2 O and gelled Ce(OH) 4 , albeit by a different solubility pathway.…”

Section: Discussionmentioning

confidence: 99%

“…However, under static liquid conditions [74], a saturated boundary layer of species of the same type as leached from the solid would have been established [37][38][39].…”

Section: Discussionmentioning

confidence: 99%

“…A critical anomaly is the observation of the maintenance of photocatalytic activity in the presence of a hydrated surface layer and possible boundary layer [74]. It would be expected that CeO 2 is required for photocatalysis but this phase is passivated and hence not present at the surface.…”

Section: Discussionmentioning

confidence: 99%

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Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

et al. 2017

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Abstract:The present work describes the effects of water on Fe-doped nanoparticulate CeO 2 , produced by flame spray pyrolysis, which represent a critical environmental issue because CeO 2 is not stable in typical atmospheric conditions. It is hygroscopic and absorbs~29 wt % water in the bulk when exposed to water vapor but, more importantly, it forms a hydrated and passivating surface layer when immersed in liquid water. In the latter case, CeO 2 initially undergoes direct and/or reductive dissolution, followed by the establishment of a passivating layer calculated to consist of~69 mol % solid CeO 2 ·2H 2 O and~30 mol % gelled Ce(OH) 4 . Under static flow conditions, a saturated boundary layer also forms but, under turbulent flow conditions, this is removed. While the passivating hydrated surface layer, which is coherent probably owing to the continuous Ce(OH) 4 gel, would be expected to eliminate the photoactivity, this does not occur. This apparent anomaly is explained by the calculation of (a) the thermodynamic stability diagrams for Ce and Fe; (b) the speciation diagrams for the Ce 4+ -H 2 O, Ce 3+ -H 2 O, Fe 3+ -H 2 O, and Fe 2+ -H 2 O systems; and (c) the Pourbaix diagrams for the Ce-H 2 O and Fe-H 2 O systems. Furthermore, consideration of the probable effects of the localized chemical and redox equilibria owing to the establishment of a very low pH (<0) at the liquid-solid interface also is important to the interpretation of the phenomena. These factors highlight the critical importance of the establishment of the passivating surface layer and its role in photocatalysis. A model for the mechanism of photocatalysis by the CeO 2 component of the hydrated phase CeO 2 ·2H 2 O is proposed, explaining the observation of the retention of photocatalysis following the apparent alteration of the surface of CeO 2 upon hydration. The model involves the generation of charge carriers at the outer surface of the hydrated surface layer, followed by the formation of radicals, which decompose organic species that have diffused through the boundary layer, if present.

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Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

“…However, under static liquid conditions [74], a saturated boundary layer of species of the same type as leached from the solid would have been established [37][38][39].…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

et al. 2017

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“…33 The other peaks are not visible due to very less loading of CeO 2 . After the growth of the ultrathin films had been verified, the electrodes were cast and assembled into coin cells to subject them to electrochemical testing.…”

Section: Resultsmentioning

confidence: 99%

Ultrathin Conductive CeO₂Coating for Significant Improvement in Electrochemical Performance of LiMn_1.5Ni_0.5O₄Cathode Materials

Patel

Palaparty

Liu

2016

J. Electrochem. Soc.

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LiMn 1.5 Ni 0.5 O 4 (LMNO) has a huge potential for use as a cathode material in electric vehicular applications. However, it could face discharge capacity degradation with cycling at elevated temperatures due to attacks by hydrofluoric acid (HF) from the electrolyte, which could cause cationic dissolution. To overcome this barrier, we coated 3-5 micron sized LMNO particles with a ∼3 nm optimally thick and conductive CeO 2 film prepared by atomic layer deposition (ALD). This provided optimal thickness for mass transfer resistance, species protection, and mitigation of cationic dissolution at elevated temperatures. After 1,000 cycles of chargedischarge between 3.5 V-5 V (vs. Li + /Li) at 55 • C, the optimally coated sample, 50Ce (50 cycles of CeO 2 ALD coated) had a capacity retention of ∼97.4%, when tested at a 1C rate, and a capacity retention of ∼83% at a 2C rate. This was compared to uncoated LMNO particles that had a capacity retention of only ∼82.7% at a 1C rate, and a capacity retention of ∼40.8% at a 2C rate. Lithium ion batteries have emerged as potential candidates for replacement of Ni-Cd batteries in electric vehicles because of their high intrinsic energy densities combined with their ease of portability. This potential creates a need for the development of new or modified cathode and anode materials that possess high energy density, long cycle life, excellent capacity retention, and a large voltage window for operation. For electric vehicles, in particular, the upper voltage cutoff window on the cathode side should be ∼5 V vs. Li + /Li. Lithium manganese nickel oxide LiMn 1.5 Ni 0.5 O 4 (LMNO) has emerged in the research community as a potential cathode material for use in electric vehicles due to its large theoretical capacity of ∼148 mAhg −1 , a high working voltage of ∼4.7 V vs. Li + /Li, and a high energy density. 1,2However, LMNO suffers from high capacity fade during performance at elevated temperatures because Mn dissolves due to generation of hydrofluoric acid (HF) in the electrolyte. 3-5The coating of surface protective layers on pristine LMNO particles has been extensively studied in literature. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] These layers provide a shield from the HF, and prevent rapid capacity fade, leading to improved cycling performance and capacity retention. Of the different surface coating techniques, atomic layer deposition (ALD) has inherent advantages that provide conformal, pin-hole free, size-tunable ultrathin films 21 and, thus, provide high capacity retention and a long life cycle. The ALD process involves a sequence of self-limiting reactions that result in a coating of one monolayer at a time. This enables size tunability at the sub-nanometer level and promotes conformity in the films. Materials like Al 2 O 3 , 17 MgF 2 , 22 TiO 2 , 18 and LiAlO 2 10 have been studied as coating materials prepared by ALD on LMNO. Even though, these materials have provided effective mitigation of cationic dissolution, the ionic conductivity of such protective layers ...

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Degradation Mechanism of Organic Dyes by Effective Transition Metal Oxide

Rani

Thamizharasan

Nayak

et al. 2020

Photocatalysts in Advanced Oxidation Processes for Wastewater Treatment

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Photocatalytic Degradation of Methyl Orange by CeO2 and Fe–doped CeO2 Films under Visible Light Irradiation

Cited by 397 publications

References 35 publications

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Ultrathin Conductive CeO₂Coating for Significant Improvement in Electrochemical Performance of LiMn_1.5Ni_0.5O₄Cathode Materials

Degradation Mechanism of Organic Dyes by Effective Transition Metal Oxide

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Photocatalytic Degradation of Methyl Orange by CeO2 and Fe–doped CeO2 Films under Visible Light Irradiation

Cited by 397 publications

References 35 publications

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Ultrathin Conductive CeO2Coating for Significant Improvement in Electrochemical Performance of LiMn1.5Ni0.5O4Cathode Materials

Degradation Mechanism of Organic Dyes by Effective Transition Metal Oxide

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Ultrathin Conductive CeO₂Coating for Significant Improvement in Electrochemical Performance of LiMn_1.5Ni_0.5O₄Cathode Materials