Phase Selective Deposition and Microstructure Control in Iron Oxide Films Obtained by Single‐Source CVD.

“…The gas phase deposition of Fe 2 O 3 layers was performed using [Fe(O t Bu) 3 ] 2 as precursor in a horizontal coldwall CVD reactor. 33,34 The precursor temperature was kept constant at 100 °C to ensure a homogeneous gas flow. The precursor flux was guided to an inductively heated (500 °C) substrate using low pressure (∼3 × 10 −6 mbar).…”

Section: Experimental Partmentioning

confidence: 99%

Electronically-Coupled Phase Boundaries in α-Fe₂O₃/Fe₃O₄ Nanocomposite Photoanodes for Enhanced Water Oxidation

Leduc

Goenuellue

Ghamgosar

et al. 2019

ACS Appl. Nano Mater.

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Photoelectrochemical (PEC) water splitting reactions are promising for sustainable hydrogen production from renewable sources. We report here, the preparation of α-Fe 2 O 3 /Fe 3 O 4 composite films via a single-step chemical vapor deposition of [Fe(O t Bu) 3 ] 2 and their use as efficient photoanode materials in PEC setups. Film thickness and phase segregation was controlled by varying the deposition time and corroborated through cross-section Raman spectroscopy and scanning electron microscopy. The highest water oxidation activity (0.48 mA/cm 2 at 1.23 V vs RHE) using intermittent AM 1.5 G (100 mW/cm 2 ) standard illumination was found for hybrid films with a thickness of 11 μm. This phenomenon is attributed to an improved electron transport resulting from a higher magnetite content toward the substrate interface and an increased light absorption due to the hematite layer mainly located at the top surface of the film. The observed high efficiency of α-Fe 2 O 3 /Fe 3 O 4 nanocomposite photoanodes is attributed to the close proximity and establishment of 3D interfaces between the weakly ferro-(Fe 2 O 3 ) and ferrimagnetic (Fe 3 O 4 ) oxides, which in view of their differential chemical constitution and valence states of Fe ions (Fe 2+ /Fe 3+ ) can enhance the charge separation and thus the overall electrical conductivity of the layer.

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“…5 Several strategies have been adopted to overcome the intrinsic limitations of hematite, for instance, tuning of electrode morphology (nanoribbons, nanobelts, nanorods, 6−8 and mesoporous layers 9,10 ), synergistic interfaces in two-dimensional stacks of semiconductors, 11 surface activation with electrocatalysts (e.g., Pt and Au), 12,13 and doping with various metal cations (Ca 2+ , Mg 2+ , Cu 2+ , Zn 2+ , Si 4+ , Ge 4+ , Ti 4+ , Pt 4+ , V 5+ , and Nb 5+ ) to change the electronic structures. 12,14−23 Nanostructuring of the α-Fe 2 O 3 thin film via various deposition techniques, such as chemical vapor deposition (CVD), 24 sol−gel, 25,26 electrospinning, 27,28 and plasma-enhanced chemical vapor deposition (PECVD), 29 can suppress the recombination processes, thereby increasing the number of photogenerated holes reaching the semiconductor−electrolyte interface and ultimately leading to a higher photocurrent density.…”

Section: ■ Introductionmentioning

confidence: 99%

High Water-Splitting Efficiency through Intentional In and Sn Codoping in Hematite Photoanodes

et al. 2016

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The effects of intermittent thin ITO layers on the water-splitting efficiency of α-Fe2O3 films grown by PECVD on FTO substrates are reported. The α-Fe2O3 was codoped with indium and tin by temperature-driven ionic transport and diffusion from the ultrathin ITO layer sputtered between the α-Fe2O3 layer and FTO substrate. The α-Fe2O3/ITO/FTO photoanodes showed a remarkable interdependence between the thickness of the ITO layer and PEC efficiency. Hematite photoanodes with a 32 nm thick ITO underlayer showed the highest photocurrent density of 2.5 mA cm–2, corresponding to an approximate 3-fold enhancement over pristine α-Fe2O3 at 1.23 V vs RHE, whereas the thinner (8 nm) ITO underlayer yielded the lowest onset potential at 0.6 V vs RHE. Although the electrode with a thicker 72 nm ITO underlayer showed a higher onset potential of 0.9 V vs RHE, it still showed an enhancement in the photocurrent density at higher bias voltages. α-Fe2O3 was also deposited on metallic titanium substrates with intermittent sputtered tin and ITO layers. The codoping with indium and tin from ITO was observed to yield greatly enhanced performance when compared with both α-Fe2O3 alone and tin-doped α-Fe2O3. Transient absorption decays in the sub-nanosecond time scale were not affected by the doping, indicating that the doping had little effect on the primary charge carrier generation and recombination. On the other hand, fewer trapped electrons on the microsecond to millisecond time scale and a greatly increased amount of long-lived surface photoholes were observed for the ITO-doped samples. The transient absorption results imply that the large increases in photoelectrochemical efficiency were obtained due to higher electron mobility, which reduces recombination and leads to more efficient electron extraction from the electrodes.

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Phase Selective Deposition and Microstructure Control in Iron Oxide Films Obtained by Single‐Source CVD.

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 5 publications

References 9 publications

Thin films by metal organic deposition of Fe–Mo–S molecular clusters: synthesis and crystal structure of [Cp2MoFe2(µ3-S)2(CO)6]

Thin films by metal organic deposition of Fe–Mo–S molecular clusters: synthesis and crystal structure of [Cp2MoFe2(µ3-S)2(CO)6]

Electronically-Coupled Phase Boundaries in α-Fe₂O₃/Fe₃O₄ Nanocomposite Photoanodes for Enhanced Water Oxidation

High Water-Splitting Efficiency through Intentional In and Sn Codoping in Hematite Photoanodes

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Phase Selective Deposition and Microstructure Control in Iron Oxide Films Obtained by Single‐Source CVD.

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 5 publications

References 9 publications

Thin films by metal organic deposition of Fe–Mo–S molecular clusters: synthesis and crystal structure of [Cp2MoFe2(µ3-S)2(CO)6]

Thin films by metal organic deposition of Fe–Mo–S molecular clusters: synthesis and crystal structure of [Cp2MoFe2(µ3-S)2(CO)6]

Electronically-Coupled Phase Boundaries in α-Fe2O3/Fe3O4 Nanocomposite Photoanodes for Enhanced Water Oxidation

High Water-Splitting Efficiency through Intentional In and Sn Codoping in Hematite Photoanodes

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Electronically-Coupled Phase Boundaries in α-Fe₂O₃/Fe₃O₄ Nanocomposite Photoanodes for Enhanced Water Oxidation