Electron trapping induced electrostatic adsorption of cations: a general factor leading to photoactivity decay of nanostructured TiO<sub>2</sub>

He, Tao; Wang, Libo; Fabregat‐Santiago, Francisco; Liu, Guoqun; Liu, Ying; Wang, Chong; Guan, Rengui

doi:10.1039/c7ta01132f

Cited by 29 publications

(27 citation statements)

References 86 publications

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“…When a −0.8 V bias was applied, sharp increase of dye adsorption amount was observed, especially in p‐TiO 2 electrodes. Similar results has been observed and attributed to surface‐defect related electron trapping in several reports [30,39] . The adsorption amount of p‐TiO 2 was about two times that of c‐TiO 2 , which was in consistent with the CV measurement results that the defect states in p‐TiO 2 NRAs was apparently higher than that of c‐TiO 2 NRAs, and also implying that electron transport would be more severely influenced in p‐TiO 2 than in c‐TiO 2 NRAs through the electron trapping induced electrostatic adsorption mechanisms.…”

Section: Resultssupporting

confidence: 90%

“…Both p‐TiO 2 and c‐TiO 2 NRAs exhibited photocurrent spike and attenuation during six cycles of measurements. This phenomenon was reported and ascribed to electron trapping induced electrostatic adsorption in our previous reports [30] . More interestingly, significant increase (∼20 fold) of photocurrent was observed in c‐TiO 2 NRAs, compared to that of p‐TiO 2 NRAs, indicating an improvement of photoelectrochemical property.…”

Section: Resultssupporting

confidence: 77%

“…This phenomen-on was reported and ascribed to electron trapping induced electrostatic adsorption in our previous reports. [30] More interestingly, significant increase (~20 fold) of photocurrent was observed in c-TiO 2 NRAs, compared to that of p-TiO 2 NRAs, indicating an improvement of photoelectrochemical property. As was mentioned above, even though aligned 1D TiO 2 nanostructures was suggested to be ideal configuration, there was still a long way to fully realize the structural superiority.…”

Section: Photoactivity Comparison Between P-tio 2 and C-tio 2 Nrasmentioning

confidence: 87%

“…Considering the significant difference in density of defect trap states between p-TiO 2 and c-TiO 2 NRAs, it is reasonable to deduce that electron trapping may still exist in single crystalline TiO 2 NRAs (in spite of the existence of a radial band bending along the rods) and thus influence the electron transport process. A facile dye adsorption strategy was proposed [30] to elucidate the surface-defects induced electron trapping process. Herein, this strategy would be employed to identify occurrence of the electron trapping induced electrostatic adsorption of cations to demonstrate the density of defects in both p-TiO 2 and c-TiO 2 NRAs.…”

Section: Electron-trapping Induced Dye Adsorptionmentioning

confidence: 99%

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Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO₂ Nanostructures: the Role of Defect States in Electron Transport Process

Han

Liu

et al. 2020

ChemElectroChem

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Electrodes made up of aligned 1D semiconductor nanostructures have drawn much attention in photoelectrochemical applications, as they are expected to be ideal configuration for channeling electrons towards the substrate without lateral electron scattering. However, efforts were hardly made to optimize the defect states in such systems. Herein, we observed significant enhancement (~20 fold) in photoelectrochemical performance of TiO 2 nanorod arrays (NRAs) after a simple calcination procedure. Through a series of structural and electrochemical characterizations, we revealed an underlying role of defects states in electron transport: even in electrodes composed of 1D TiO 2 nanorods, lateral electron scattering would be avoided, which was confirmed by measuring the trapfree electron diffusion coefficient (D 0), the electron transport process can be severely affected by defect states distributed in the band gap. The calcination procedure can bring structural optimization for TiO 2 NRAs, therefore facilitates electron transport process. Intrinsically, this work provides a structural view for realizing the superior performance of aligned 1D semiconductor nanostructures.

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 77%

Section: Photoactivity Comparison Between P-tio 2 and C-tio 2 Nrasmentioning

confidence: 87%

Section: Electron-trapping Induced Dye Adsorptionmentioning

confidence: 99%

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Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO₂ Nanostructures: the Role of Defect States in Electron Transport Process

Han

Liu

et al. 2020

ChemElectroChem

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“…45,46 We attribute the slow growth of E3 in water-poor media to a steady increase of the local proton concentration at the electrode-solution interface upon cycling (as previously observed for metal oxides), which favours the PCET mechanism and further allows for the observed cycle-dependent behaviour in Supplementary Figure 17. 47,48 This hypothesis is supported by the disappearance of wave E3 upon restoring the electrode to its initial state by allowing equilibration at open-circuit conditions (Figure 5a). As such, in such a water-poor medium, we attribute the origin of the oxidation wave of C seen in the first scan to the protonation of…”

Section: Mechanistic Studies Of Immobilised Cotpypmentioning

confidence: 77%

Solar-driven reduction of aqueous CO2 with a cobalt bis(terpyridine)-based photocathode

et al. 2019

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The selective reduction of CO2 with inexpensive solar-driven photoelectrochemical devices is a contemporary challenge in the quest for renewable fuel production. Here we report a molecular catalyst-based photocathode assembled from precious-metal-free components that is active towards solar-driven, aqueous CO2 reduction. The reported photocathode is based on a phosphonated cobalt bis(terpyridine) catalyst that is interfaced via a mesoporous TiO2 scaffold with a light-harvesting p-type silicon electrode. The hybrid photoelectrode reduces CO2 to CO in both organic-water and purely aqueous conditions, achieving a turnover number of ~330 and maintaining stable activity for more than one day. Critically, indepth electrochemical and in situ resonance Raman and infrared spectroelectrochemical investigations alluded to a catalytic mechanism that differs to that reported for the soluble metal bis(terpyridine) catalyst as the consequence of the immobilisation. In addition, it further unlocks an earlier catalytic onset and better electrocatalytic performance while enabling aqueous CO2 reduction with the reported photocathode.

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Electrochromic Performance Fading and Restoration in Amorphous TiO₂ Thin Films

Huang

Zhang

Shao

et al. 2022

Advanced Optical Materials

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electrons filling the conduction band. [11][12][13] Optical transmittance returns to its original state when electrons, associated with the ions, are extracted. Recent advances show dual band electrochromic TiO x has also been developed through doping [6,14] or oxygen vacancy manipulation [4] thanks to localized surface plasmon resonance. [9] However, similar to other inorganic electrochromic oxides, [15][16][17] TiO 2 thin films suffer from performance degradation, that is, charge capacity fading associated with optical modulation (denoted as T bleached −T colored ) shrinking upon electrochemical cycling. Although considerable strategies (such as doping, nanostructure modification etc.) have been employed to improve the cycling stability, the decay of electrochromic performance is still inevitable . Recently, it emerged that aged WO 3 and TiO 2 thin films can regain their initial electrochromic performance through a galvanostatic detrapping process, [5,15] providing a general strategy to extend the lifetime of electrochromic materials. [18][19][20] This points out that, in addition to the reversible ion intercalation, ion trapping and detrapping also occur in the amorphous solid state matrix. Origins of traps and their associated dynamics in determining the electrochromic performance, although highly appealing for both fundamental physics and practical applications, remain blank.In this paper, we show that, both ion trapping and detrapping in amorphous TiO 2 couple to a variety of process occurring. α-traps and modified α-traps (possess higher energy barrier than α-traps) are non-absorbing sites showing to only degrade the colored state, where β-traps are absorbing sites presenting to degrade the bleached state of TiO 2 thin films. More importantly, the origin of all the traps and their energy barrier comparison are clearly revealed. The transition between reversible sites and traps are also demonstrated to be reversible through ion trapping and detrapping processes. This study provides a general picture for ion trapping and detrapping in amorphous TiO 2 thin films and may pave the way for better understanding other ion exchange based systems or devices. Results and Discussion α-Traps in TiO 2 Thin FilmsElectrochromic TiO 2 thin films were deposited by direct reactive magnetron sputtering with a thickness of 270 ± 20 nm Electrochromic performance fading is inevitable upon extended cycling, and the limited lifetime greatly prevents large-scale commercialization of electrochromism-based devices. Here the origin of the performance degradation is uncovered and the performance restoration in TiO 2 thin films is explored. It is shown that, depending on the applied potential windows, the inserted ions are immobilized in α-traps resulting in a monotonous degradation of colored state, or immobilized in band modified α-traps leading to mutual degradation of colored and bleached state of the films. It is found by releasing the resided ions in various traps, the initial performance can be restored accordingly. Moreover, rev...

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Electron trapping induced electrostatic adsorption of cations: a general factor leading to photoactivity decay of nanostructured TiO₂

Cited by 29 publications

References 86 publications

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO₂ Nanostructures: the Role of Defect States in Electron Transport Process

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO₂ Nanostructures: the Role of Defect States in Electron Transport Process

Solar-driven reduction of aqueous CO2 with a cobalt bis(terpyridine)-based photocathode

Electrochromic Performance Fading and Restoration in Amorphous TiO₂ Thin Films

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Electron trapping induced electrostatic adsorption of cations: a general factor leading to photoactivity decay of nanostructured TiO2

Cited by 29 publications

References 86 publications

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO2 Nanostructures: the Role of Defect States in Electron Transport Process

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO2 Nanostructures: the Role of Defect States in Electron Transport Process

Solar-driven reduction of aqueous CO2 with a cobalt bis(terpyridine)-based photocathode

Electrochromic Performance Fading and Restoration in Amorphous TiO2 Thin Films

Contact Info

Product

Resources

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Electron trapping induced electrostatic adsorption of cations: a general factor leading to photoactivity decay of nanostructured TiO₂

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO₂ Nanostructures: the Role of Defect States in Electron Transport Process

Toward the Intrinsic Superiority of Aligned One‐Dimensional TiO₂ Nanostructures: the Role of Defect States in Electron Transport Process

Electrochromic Performance Fading and Restoration in Amorphous TiO₂ Thin Films