Investigation of Regeneration Kinetics of a Carbon-Dot-Sensitized Metal Oxide Semiconductor with Scanning Electrochemical Microscopy

Liu, Naiyun; Qin, Yunlong; Han, Mumei; Li, Hao; Sun, Yue; Zhao, Siqi; Huang, Hui; Liu, Yang; Kang, Zhenhui

doi:10.1021/acsaem.7b00292

Cited by 7 publications

(7 citation statements)

References 45 publications

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“…Consequently, the addition of C-dots to metal oxides increases their performance . This view shows that C-dots can enhance electron transfer and reduce charge recombination because they serve as an energy donor in electrochemical devices such as supercapacitors and DSSCs . Incidentally, recent work has reported that the PCE of a ZnO DSSC increases from 0.8 to 5.9% following the addition of C-dots .…”

Section: Introductionmentioning

confidence: 99%

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Etefa

Imae

Yanagida

2020

ACS Appl. Mater. Interfaces

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In this work, the effect of carbon dots (C-dots) on the performance of NiO-based dye-sensitized solar cells (DSSCs) was explored. NiO nanoparticles (NPs) with a rectangular shape (average size: 11.4 × 16.5 nm2) were mixed with C-dots, which were synthesized from citric acid (CA) and ethylenediamine (EDA). A photocathode consisting of a composite of C-dots with NiO NPs (NiO@C-dots) was then used to measure the photovoltaic performance of a DSSC. A power conversion efficiency (PCE) of 9.85% (430 nm LED@50 mW/cm2) was achieved by a DSSC fabricated via the adsorption of N719 sensitizer with a C-dot content of 12.5 wt % at a 1.5:1 EDA/CA molar ratio. This PCE value was far larger than the PCE value (2.44 or 0.152%) obtained for a NiO DSSC prepared without the addition of C-dots or N719, respectively, indicating the synergetic effect by the co-adsorption of C-dots and N719. This synergetically higher PCE of the NiO@C-dot-based DSSC was due to the larger amount of sensitizer adsorbed onto the composites with a larger specific surface area and the faster charge transfer in the NiO@C-dot working electrode. In addition, the C-dots bound to the NiO NPs shorten the band gap of the NiO NPs due to energy transfer and give rise to faster charge separation in the electrode. The most important fact is that C-dots are the main sensitizer, while N719 tightly adsorbs on C-dots and NiO behaves as an accelerator of a positive electron transfer and a restrainer of the electron–hole recombination. These results reveal that C-dots are a remarkable enhancer for NiO NPs in DSSCs and that NiO@C-dots are promising photovoltaic electrode materials for DSSCs.

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Section: Introductionmentioning

confidence: 99%

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Etefa

Imae

Yanagida

2020

ACS Appl. Mater. Interfaces

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“…Specifically, upon illumination with visible light, rich Based on this finding, we further synthesized a system composed of CDs and TiO 2 , and scanning electrochemical microscopy (SECM) in feedback mode was employed to probe the transfer kinetics of photoinduced electrons along the interface during the photosensitized reaction (Figure 5C). 29 It was found that upon photoexcitation of the CDs, the electrons were injected into the CB of TiO 2 . When the ultramicroelectrode (UME) approached the substrate, the resulting CD oxidized state (CD + ) was regenerated by the produced I − in the electrolyte.…”

Section: Photoinduced Potential In Cdsmentioning

confidence: 99%

“…This finding demonstrated the feasibility of photoinduced potential in thermodynamics for CD-based composites. Based on this finding, we further synthesized a system composed of CDs and TiO 2 , and scanning electrochemical microscopy (SECM) in feedback mode was employed to probe the transfer kinetics of photoinduced electrons along the interface during the photosensitized reaction (Figure C) . It was found that upon photoexcitation of the CDs, the electrons were injected into the CB of TiO 2 .…”

Section: Diversity Of Photoelectrochemical Propertiesmentioning

confidence: 99%

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Diversity and Tailorability of Photoelectrochemical Properties of Carbon Dots

2022

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Conspectus As a new kind of carbon based functional material, carbon dots (CDs) have sparked much interest in recent years. The tunable structure, composition, and morphology of CDs unlocks opportunities to enable diversity in their photoelectrochemical properties, and thus they show great potential in various applications such as biology, catalysis, sensors, and energy storage. Nevertheless, the related understanding of CDs is insufficient at present due to their inherent complexity of microstructure, which involves the intersection of high polymer, bulk carbon, and quantum dot (QD). A good understanding of the underlying mechanism behind the properties of CDs is still a formidable challenge, requiring the integration of robust knowledge from organic chemistry, materials science, and solid state physics. Within this context, discovering more appealing properties, elucidating fundamental factors that affect the properties and proposing effective engineering strategies that can realize specific functions for CDs are now highly pursued by researchers. At the beginning of this Account, the main features of CDs are introduced, where not only the basic structural, compositional and morphological characteristics but also the rich photoelectrochemical properties are elucidated, among which the band gap, chirality, photoinduced potential, and electron sink effect are particularly emphasized. Furthermore, new analysis techniques including transient photoinduced current (TPC), transient photoinduced voltage (TPV), and machine learning (ML) to reveal the unique properties of CDs are described. Then, several appealing strategies that aim to rationally tailor CDs for oriented applications are highlighted. These regulation strategies are morphology modulation (e.g., developing CDs with new geometrical configuration, controlling the particle size), phase engineering (e.g., altering the phase crystallinity, introducing the foreign atoms), surface functionalization (e.g., grafting various types of functional groups), and interfacial tuning (e.g., building CD-based nanohybrids with well-defined interfaces). Although the fundamental investigation of CDs is relatively undeveloped because of their complexity, this does not hinder their wide application. At the same time, exploring the extensive applications of CDs will promote their in-depth understanding. Finally, the chances for building a CD-centered blueprint for sustainable society are explored and challenges for future research in the field of CDs are proposed as follows: (i) the controllable synthesis of CDs with uniform size; (ii) search for novel CDs with unique structure, morphology, or composition; (iii) quantitative understanding of the property of CDs; (iv) performance enhancement by external forces such as magnetism or heat injection; (v) construction of the dual carbon concept; (vi) further research on different photocatalytic applications. On the whole, this Account may provide meaningful references for the understanding of the microstructure–property correlation as w...

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“…Such composite systems could be devised using myriad different approaches, e.g., by (a) loading TiO 2 on carbon materials, , (b) doping TiO 2 with elemental carbon, , and (c) coating TiO 2 with various forms of carbon. , Moreover, the mechanism of carrier transport and separation in such TiO 2 –carbon composites can also be distinctly different, depending on the device configuration as well as morphology of the composite. It has been demonstrated that carbon localization on TiO 2 can lead to two distinct phenomena: (a) carbon materials can donate electrons to the conduction band of TiO 2 ; this constitutes the “classic” sensitizer configuration where TiO 2 constructs the carrier transport channel , and (b) carbon materials can act as electron collector to capture photoexcited electrons from TiO 2 ; in this case, the carrier transport occurs through the carbon material. , These coexisting opposing phenomena may hinder or boost device performance; an interesting implementation of this has been demonstrated in a study by Yu et al, where, in a single system, the carbon material acts as an electron reservoir under UV radiation and as a sensitizer under visible light. Thus, rational designing of the composite plays a very significant role in dictating the final performance of such composite devices.…”

Section: Introductionmentioning

confidence: 99%

Band-Edge Engineering at the Carbon Dot–TiO₂ Interface by Substitutional Boron Doping

2019

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We investigated the heterostructures of pristine and boron-doped carbon dots (CDs) with TiO 2 using a first principles approach. Heterojunctions of CDs and TiO 2 demonstrated type II band alignments that promote spatial separation of charge carriers and were well suited for sensitizer configuration. However, large CD band gaps severely restricted their optical efficiencies. Substitutional boron doping of the CDs introduced new electronic states and pulled the CDs' conduction band minimum (CBM) down, resulting in dramatic reduction of CD band gaps (by 48− 57%). The resulting band alignment of the boron-doped CD− TiO 2 heterostructures were found to be type I, in which CBM and valence band maximum of TiO 2 straddled those of CDs and photoexcited carriers could migrate to CD side. This indicated better suitability for device configurations where conducting channel lies through the CDs but elevated the chance of recombination loss. However, the internal electric fields at these heterojunctions were found to selectively promote electron migration and hinder hole migration, which we postulate could counter the recombination loss in these systems. The obtained results offer insights into designing a new generation of watersplitting photocatalysts that would be able to utilize a broader spectrum of solar radiation than the current solutions.

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Investigation of Regeneration Kinetics of a Carbon-Dot-Sensitized Metal Oxide Semiconductor with Scanning Electrochemical Microscopy

Cited by 7 publications

References 45 publications

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Diversity and Tailorability of Photoelectrochemical Properties of Carbon Dots

Band-Edge Engineering at the Carbon Dot–TiO₂ Interface by Substitutional Boron Doping

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Investigation of Regeneration Kinetics of a Carbon-Dot-Sensitized Metal Oxide Semiconductor with Scanning Electrochemical Microscopy

Cited by 7 publications

References 45 publications

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Diversity and Tailorability of Photoelectrochemical Properties of Carbon Dots

Band-Edge Engineering at the Carbon Dot–TiO2 Interface by Substitutional Boron Doping

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Resources

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Band-Edge Engineering at the Carbon Dot–TiO₂ Interface by Substitutional Boron Doping