Low temperature atomic layer deposition of highly photoactive hematite using iron(iii) chloride and water

Klug, Jeffrey A.; Becker, Nicholas; Riha, Shannon C.; Martinson, Alex B. F.; Elam, Jeffrey W.; Pellin, Michael J.; Proslier, Thomas

doi:10.1039/c3ta12514a

Cited by 39 publications

(40 citation statements)

References 30 publications

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“…The same can be said for the photocatalytic activity of the as-prepared Si/Fe 2 O 3 /Co 27 films (Figure 2b). [58] We hypothesize that as the annealing of the Si/Fe 2 O 3 film does not change the film's performance, the improvement in the annealed Si/Fe 2 O 3 /Co 27 sample (Figures 2a nd 3) may be ar esult of improved charge transfer between the film and the cluster moiety.A sp ointed out in the Experimental Section, grazing incidence X-ray absorptionn ear-edge spectroscopy (GIXANES)datadon ot indicateasubstantial change in compo-sition/structure of the clusters. This result has two interesting implications: 1) the original surfacec overage of activeF e 2 O 3 water oxidation sites must be less than the 5% of the Figure 2b).…”

Section: Oer Activity Of Co 27 Clustersmentioning

confidence: 91%

“…[57,58,59] Previously,w eh ave studied the electrochemical activityo ft hese films [58] and of films coatedw ith thin (% monolayer) layers of ALD-grown cobalta nd found them to be reasonably active water oxidation catalysts in their own right. [57,58,59] Previously,w eh ave studied the electrochemical activityo ft hese films [58] and of films coatedw ith thin (% monolayer) layers of ALD-grown cobalta nd found them to be reasonably active water oxidation catalysts in their own right.…”

Section: Fe 2 O 3 Depositionmentioning

confidence: 99%

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Water Oxidation by Size‐Selected Co₂₇ Clusters Supported on Fe₂O₃

et al. 2016

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The complexity of the water oxidation reaction makes understanding the role of individual catalytic sites critical to improving the process. Here, size-selected 27-atom cobalt clusters (Co ) deposited on hematite (Fe O ) anodes were tested for water oxidation activity. The uniformity of these anodes allows measurement of the activity of catalytic sites of well-defined nuclearity and known density. Grazing incidence X-ray absorption near-edge spectroscopy (GIXANES) characterization of the anodes before and after electrochemical cycling demonstrates that these Co clusters are stable to dissolution even in the harsh water oxidation electrochemical environment. They are also stable under illumination at the equivalent of 0.4 suns irradiation. The clusters show turnover rates for water oxidation that are comparable or higher than those reported for Pd- and Co-based materials or for hematite. The support for the Co clusters is Fe O grown by atomic layer deposition on a Si chip. We have chosen to deposit a Fe O layer that is only a few unit cells thick (2 nm), to remove complications related to exciton diffusion. We find that the electrocatalytic and the photoelectrocatalytic activity of the Co /Fe O material is significantly improved when the samples are annealed (with the clusters already deposited). Given that the support is thin and that the cluster deposition density is equivalent to approximately 5 % of an atomic monolayer, we suggest that annealing may significantly improve the exciton diffusion from the support to the catalytic moiety.

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Section: Oer Activity Of Co 27 Clustersmentioning

confidence: 91%

Section: Fe 2 O 3 Depositionmentioning

confidence: 99%

Water Oxidation by Size‐Selected Co₂₇ Clusters Supported on Fe₂O₃

et al. 2016

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“…Solar water splitting in PEC cells has emerged as a clean and cost‐effective method for the sustainable production of H 2 in view of different applications . Among the different metal oxides studied as photoanodes, hematite (α‐Fe 2 O 3 ) displays promising properties for PEC water oxidation . In addition to its band gap of ≈2.1 eV, enabling it to absorb an appreciable fraction of the solar spectrum, hematite possesses a good chemical stability in aqueous environments, a large abundance and a valence band edge position suitable for H 2 O oxidation .…”

Section: Introductionmentioning

confidence: 99%

Interplay of thickness and photoelectrochemical properties in nanostructured α-Fe₂ O₃ thin films

Warwick

Carraro

Gasparotto

et al. 2015

Phys. Status Solidi A

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Nanostructured Fe 2 O 3 thin films were grown by plasma enhanced-chemical vapor deposition (PE-CVD) from Ar/O 2 plasmas for photoelectrochemical (PEC) water splitting applications. Iron oxide coatings were deposited on fluorinedoped tin oxide (FTO) substrates at 300 8C under optimized conditions, and subsequently annealed ex situ in air at 650 8C. Structural and compositional analyses confirmed the formation of pure a-Fe 2 O 3 (hematite), free from other crystalline iron oxide phases. Controlled variations of the deposition time enabled tuning of the thickness and nano-aggregate sizes in the resulting deposits and, correspondingly, their current-voltage characteristics. A maximum photocurrent density close to 1 mA cm À2 was achieved at 1.23 V versus the reversible hydrogen electrode (RHE), without the need of any oxygen evolution catalyst or over/underlayer. The present findings revealed the key role played by the engineering of Fe 2 O 3 -based nanomaterials, resulting ultimately in a lowered carrier diffusion length, and in an optimal diffusion of tin from FTO into thinner layers. These features offer an amenable opportunity for harvesting radiant energy to trigger water photoelectrolysis and produce clean hydrogen in a carbonneutral fashion.

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“…[24][25][26] Hematite is an abundant, cheap, and nontoxic PEC semiconductor for water splitting [27] that has served for a long time as a model system for studying oxidation kinetics of water (four-electron process) [28] or of simpler one-electron redox couples. [29] It continues to raise interest with respect to nanostructuring but also forming pn-junctions for enlarged charge collection.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Optical Losses in a Photoelectrochemical Cell: A Tool for Precise Absorptance Estimation

Cendula

Steier

Losio

et al. 2017

Adv Funct Materials

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Optical losses in a photoelectrochemical (PEC) cell account for a substantial part of solar-to-hydrogen conversion losses, but limited attention is paid to the detailed investigation of optical losses in PEC cells. In this work, an optical model of combined coherent and incoherent light propagation in all layers of the PEC cell based on spectroscopic measurements is presented. Specifically, photoelectrodes using transparent conductive substrates such as F:SnO 2 coated with thin absorber films are focused. The optical model is verified for hematite photoanodes fabricated by atomic layer deposition and successfully used to determine wavelength-dependent reflection, transmission, layer absorptances, and charge generation rates. Furthermore, the calculated absorptances enable 20-30% more accurate calculations of the absorbed photon-to-current efficiency of PEC cells. Our optical model is a powerful tool for the optimization of the optical performance of PEC cells focusing on single absorber or tandem configurations and represents a cornerstone of a complete (optical and electrical) model for PEC water splitting cells.

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Low temperature atomic layer deposition of highly photoactive hematite using iron(iii) chloride and water

Cited by 39 publications

References 30 publications

Water Oxidation by Size‐Selected Co₂₇ Clusters Supported on Fe₂O₃

Water Oxidation by Size‐Selected Co₂₇ Clusters Supported on Fe₂O₃

Interplay of thickness and photoelectrochemical properties in nanostructured α-Fe₂ O₃ thin films

Analysis of Optical Losses in a Photoelectrochemical Cell: A Tool for Precise Absorptance Estimation

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Low temperature atomic layer deposition of highly photoactive hematite using iron(iii) chloride and water

Cited by 39 publications

References 30 publications

Water Oxidation by Size‐Selected Co27 Clusters Supported on Fe2O3

Water Oxidation by Size‐Selected Co27 Clusters Supported on Fe2O3

Interplay of thickness and photoelectrochemical properties in nanostructured α-Fe2 O3 thin films

Analysis of Optical Losses in a Photoelectrochemical Cell: A Tool for Precise Absorptance Estimation

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Water Oxidation by Size‐Selected Co₂₇ Clusters Supported on Fe₂O₃

Water Oxidation by Size‐Selected Co₂₇ Clusters Supported on Fe₂O₃

Interplay of thickness and photoelectrochemical properties in nanostructured α-Fe₂ O₃ thin films