The role of carbon dots – derived underlayer in hematite photoanodes

Guo, Qian; Luo, Hui; Zhang, Jifang; Ruan, Qiushi; Periasamy, Arun Prakash; Fang, Yuanxing; Xie, Zailai; Li, Tongtong; Wang, Xinchen; Tang, Junwang; Briscoe, Joe; Titirici, Magdalena; Sobrido, Ana Jorge

doi:10.1039/d0nr06139e

Cited by 11 publications

(9 citation statements)

References 79 publications

(136 reference statements)

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“…The hole transfer rate constants k tr and surface recombination rate constants k rec at the α-Fe 2 O 3 /electrolyte interface under various potentials calculated from these spectra are shown in Figure 4c,d, respectively. 40 The values of k tr and k rec for α-Fe 2 O 3 indicate an order of magnitude slower hole transfer than charge recombination in that system. k tr gradually increases with increasing potential, while k rec decreases.…”

Section: ■ Results and Discussionmentioning

confidence: 88%

“…The high-frequency arc in the fourth quadrant reflects the attenuation of the PEC system caused by the series resistance and capacitances, while the low-frequency arc is related to charge transfer and recombination. The hole transfer rate constants k tr and surface recombination rate constants k rec at the α-Fe 2 O 3 /electrolyte interface under various potentials calculated from these spectra are shown in Figure c,d, respectively . The values of k tr and k rec for α-Fe 2 O 3 indicate an order of magnitude slower hole transfer than charge recombination in that system.…”

Section: Resultsmentioning

confidence: 97%

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Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?

et al. 2023

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Single-atom catalysts (SACs) on hematite photoanodes are efficient cocatalysts to boost photoelectrochemical performance. They feature high atom utilization, remarkable activity, and distinct active sites. However, the specific role of SACs on hematite photoanodes is not fully understood yet: Do SACs behave as a catalytic site or as a spectator? By combining spectroscopic experiments and computer simulations, we demonstrate that single-atom iridium (sIr) catalysts on hematite (α-Fe2O3/sIr) photoanodes act as a true catalyst by trapping holes from hematite and providing active sites for the water oxidation reaction. In situ transient absorption spectroscopy showed a reduced number of holes and shortened hole lifetime in the presence of sIr. This was particularly evident on the second timescale, indicative of fast hole transfer and depletion toward water oxidation. Intensity-modulated photocurrent spectroscopy evidenced a faster hole transfer at the α-Fe2O3/sIr/electrolyte interface compared to that at bare α-Fe2O3. Density functional theory calculations revealed the mechanism for water oxidation using sIr as a catalytic center to be the preferred pathway as it displayed a lower onset potential than the Fe sites. X-ray photoelectron spectroscopy demonstrated that sIr introduced a mid-gap of 4d state, key to the fast hole transfer and hole depletion. These combined results provide new insights into the processes controlling solar water oxidation and the role of SACs in enhancing the catalytic performance of semiconductors in photo-assisted reactions.

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Section: ■ Results and Discussionmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 97%

Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?

et al. 2023

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“…62 Therefore, a variety of strategies have been attempted to increase the minority diffusion length, such as nano-structuring, doping, and others. [79][80][81] The chemical reactivity of Fe 2 O 3 leads to conventional modifications of its physicochemical properties. For instance, Fe 2 O 3 crystal films can be realized by microwave-assisted annealing by forming the porosity of an abundantly wormlike network (Fig.…”

Section: Traditional Metal Oxidesmentioning

confidence: 99%

Sustainable photoanodes for water oxidation reactions: from metal-based to metal-free materials

Wang

Cui

et al. 2022

Chem. Commun.

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“…They were loaded onto FTO substrates, and Fe 2 O 3 films were grown on CDs. As a photoanode, CDs facilitate the photoexcitation charge separation and transfer of Fe 2 O 3 to improve PD . In this work, IMPS was acquired to study the transfer of photoexcited charge.…”

Section: Metal-free Materials For Other Functional Layersmentioning

confidence: 99%

“…As a photoanode, CDs facilitate the photoexcitation charge separation and transfer of Fe 2 O 3 to improve PD. 61 In this work, IMPS was acquired to study the transfer of photoexcited charge. Significant enhancements in the hole transfer rate constant and the reduced surface charge recombination rate constant can be obtained to confirm the improved dynamics of charges by the assistance of CDs in the photoanode.…”

Section: Metal-free Materials As Conductive Layersmentioning

confidence: 99%

Roles of Metal-Free Materials in Photoelectrodes for Water Splitting

Wang

Fang

et al. 2021

Acc. Mater. Res.

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Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: Photoelectrochemical (PEC) water splitting is an appealing approach to the hydrogen evolution reaction since it converts sunlight in the form of hydrogen fuel, which has the potential to revolutionize the fossil fuel-based energy systems of the modern society. In the last half century, progress has been made with respect to the material, synthesis, and system. Recent developments of multilayered photoelectrodes have made a breakthrough to improve the sunlight conversion efficiency and strengthen the physiochemical stability. The exploration of new materials for the functional layers of photoelectrodes offers a new opportunity for practical application. Among the emerging materials, metal-free species have shown superior properties, such as high stability, sustainability, and renewability. With respect to inorganic materials, their physiochemical properties can be readily regulated, including thermodynamics and kinetics, and thus increasing attention has been devoted. In this Account, the functional components of a photoelectrodes are specified, namely conductive layers for charge separation and transfer, photocatalytic layers for light absorption, passivation layers for protection of the electrode, and cocatalysts for the acceleration of the surface reaction. We have focused metal-free materials for the functional layers, including the (1) carbon cloth and carbon quantum dots (CQDs) for the conductive layer, 2) polymeric carbon nitrides (PCNs), carbon doped boron nitride, and covalent organic frameworks for photocatalytic layers, and (3) CQDs and black phosphorene for cocatalysts. We aim to identify the relationship between the function of the metal-free materials and the performance of the water splitting reaction. With respect to the outlook, discussions have been presented for the further development of metal-free materials to improve the performance of each functional layer. Despite the fact that the use of metal-free materials for PEC water splitting is still in its infancy, this Account not only provides new thoughts and opportunities to pursue an improved performance for the water-splitting reaction but also stimulates advanced applications by using metal-free PEC systems.

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The role of carbon dots – derived underlayer in hematite photoanodes

Abstract: Hematite is a promising candidate as photoanode for solar-driven water splitting, with a theoretically predicted maximum solar-to-hydrogen conversion efficiency of ~ 16%. However, the interfacial charge transfer and recombination greatly...

Cited by 11 publications

References 79 publications

Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?

Single-Atom Iridium on Hematite Photoanodes for Solar Water Splitting: Catalyst or Spectator?

Sustainable photoanodes for water oxidation reactions: from metal-based to metal-free materials

Roles of Metal-Free Materials in Photoelectrodes for Water Splitting

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