Influence of Sn4+ and Sn4+/Mg2+ doping on structural features and visible absorption properties of α-Fe2O3 hematite

Gaudon, Manuel; Pailhé, N.; Majimel, Jérôme; Wattiaux, A.; Abel, J.; Demourgues, Alain

doi:10.1016/j.jssc.2010.04.043

Cited by 45 publications

(29 citation statements)

References 27 publications

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“…For nanostructures synthesized by the wet route, the estimated values of cell volume were typically less than those observed for standard hematite, whicha re related to bulk hematite. [16] However, for tin-modified hematite electrodes, as mall reduction in the cell volume was observed ( Table 1) relative to that for pure hematite electrodes, as well as that observed in the JCPDSp attern;t his was attributed to changes caused by the segregation of the Sn 4 + precursor.The incorporation of different elements during the preparation of hematite films by differentc hemical methods is knownt or esult in ar eduction of crystallite size instead of ad esirable doping effect. For instance,t he reduction of crystallite size during thermalt reatment, which consequently decreases the cell volume, can be attributed to the segregation of incorporatede lements preventingc rystal growth.…”

Section: Resultsmentioning

confidence: 78%

“…The values obtained for the lattice parameters remained virtually unchanged for the pure and tin‐modified hematite electrodes grown at different times with additional thermal treatment. These values were in agreement with those previously reported for nanostructures of pure hematite electrodes, with a and c values recorded on JCPDS card no. 33‐0664, including the slight difference in the cell volume (see Table ).…”

Section: Resultsmentioning

confidence: 97%

“…33‐0664, including the slight difference in the cell volume (see Table ). For nanostructures synthesized by the wet route, the estimated values of cell volume were typically less than those observed for standard hematite, which are related to bulk hematite . However, for tin‐modified hematite electrodes, a small reduction in the cell volume was observed (Table ) relative to that for pure hematite electrodes, as well as that observed in the JCPDS pattern; this was attributed to changes caused by the segregation of the Sn 4+ precursor.…”

Section: Resultsmentioning

confidence: 99%

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Hematite Surface Activation by Chemical Addition of Tin Oxide Layer

Carvalho

Souza

2016

ChemPhysChem

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In this study, the effect of tin (Sn(4+) ) modification on the surface of hematite electrodes synthesized by an aqueous solution route at different times (2, 5, 10, 18, and 24 h) is investigated. As confirmed from X-ray diffraction results, the as-synthesized electrode exhibits an oxyhydroxide phase, which is converted into a pure hematite phase after being subjected to additional thermal treatment at 750 °C for 30 min. The tin-modified hematite electrode is prepared by depositing a solution of Sn(4+) precursor on the as-synthesized electrode, followed by thermal treatment under the same abovementioned conditions. This modification results in an enhancement of the photocurrent response for all hematite electrodes investigated and attains the highest values of around 1.62 and 2.3 mA cm(-2) at 1.23 and 1.4 V versus RHE, respectively, for electrodes obtained in short synthesis times (2 h). Contact angle measurements suggest that the deposition of Sn(4+) on the hematite electrode provides a more hydrophilic surface, which favors a chemical reaction at the interface between the electrode and electrolyte. This result generates new perspectives for understanding the deposition of Sn(4+) on the hematite electrode surface, which is in contrast with several studies previously reported; these studies state that the enhancement in photocurrent density is related to either the induction of an increased donor charge density or shift in the flat-band potential, which favors charge separation.

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Section: Resultsmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

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Hematite Surface Activation by Chemical Addition of Tin Oxide Layer

Carvalho

Souza

2016

ChemPhysChem

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“…[ 56 ] To further improve the photoactivity of hematite photoanode, element doping has been extensively studied to improve the structural, electronic and optical properties of hematite. The role of dopants, such as Ti, [ 65,[68][69][70][71][72][73][74][75] Si, [ 68,[76][77][78][79] Al, [ 71,80 ] Mg, [ 81,82 ] Zn, [ 71,78 ] Be, [ 80 ] Mo, [ 83 ] and Sn, [ 4,61,69,80,81,[84][85][86][87][88][89][90] on the PEC performance of hematite have been investigated. Recently, there is an increasing interest of developing Sn-doped hematite nanostructured photoanode due to the signifi cant effect of Sn doping on the photoactivity of hematite.…”

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confidence: 99%

Review of Sn‐Doped Hematite Nanostructures for Photoelectrochemical Water Splitting

Ling

2014

Part & Part Syst Charact

106

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Hematite (α-Fe 2 O 3 ) nanostructures have been extensively studied as photoanodes for photoelectrochemical (PEC) water splitting. However, the photoactivity of pristine hematite nanostructures is limited by a number of factors, including poor electrical conductiviy and slow oxygen evolution reaction kinetics. Previous studies have shown that using tin (Sn) as an n-type dopant can substantially enhance the photoactivity of hematite photoanodes by modifying their optical and electrical properties. Here, the recent accomplishments in using Sn-doped hematite photoanodes for solar water splitting are highlighted.1.9-2.2 eV [ 59 ] for harvesting solar light, which corresponding to a high theoretical STH conversion effi ciency of 14%-17%. [ 60 ] Iron is the fourth most abundant element in the Earth's crust (6.3% by weight), [ 5 ] and hematite is a low-cost material. In addition, hematite is chemically stable in solutions of different pH. [ 61 ] However, the STH conversion effi ciencies of reported hematite photoanodes are considerably lower than the theoretical value, owing to its very short-excited state lifetime (<10 ps), [ 62 ] short hole diffusion length (≈2-4 nm), [ 5,61 ] poor surface oxygen evolution reaction kinetics, [ 63 ] and poor electrical conductivity (10 −6 Ω −1 cm −1 ). [ 5 ] The recent development of hematite nanostructures, including nanoparticles, [ 59,64,65 ] nanowires [ 66,67 ] and nanonets, [ 56,58 ] opens up new opportunities in addressing the abovementioned limitations. Nanostructured photoanode offers increased semiconductor/electrolyte interfacial area for water oxidation, as well as substantially reduced diffusion length for minority carriers. Therefore, nanostructured hematite photoelectrodes are expected to be more effi cient in charge carrier collection than their bulk counterparts. [ 60 ] For example, Lin et al. reported the growth of ultrathin hematite fi lm (25 nm) on a conductive nanonet structure. The nanonet-based hematite photoanode achieved an excellent photocurrent of 1.6 mA cm −2 at 1.23 V versus RHE, which is four times higher than the value obtained from the planar sample with the same thickness. The photocurrent enhancement was due to the increased activation sites for water oxidation ( Figure 2 ). [ 56 ] To further improve the photoactivity of hematite photoanode, element doping has been extensively studied to improve the structural, electronic and optical properties of hematite. The role of dopants, such as Ti, [ 65,[68][69][70][71][72][73][74][75] Si, [ 68,[76][77][78][79] Al, [ 71,80 ] Mg, [ 81,82 ] Zn, [ 71,78 ] Be, [ 80 ] Mo, [ 83 ] and Sn, [ 4,61,69,80,81,[84][85][86][87][88][89][90] on the PEC performance of hematite have been investigated. Recently, there is an increasing interest of developing Sn-doped hematite nanostructured photoanode due to the signifi cant effect of Sn doping on the photoactivity of hematite. Sn 4+ is a tetravalent dopant that can be substitutionally doped into hematite at the Fe 3+ sites. [ 69,71,89 ] The electrical conductivity of Sn-doped hema...

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“…The Raman spectroscopy experiments were carried out in Renishaw micro Raman with the excitation wavelength of 633 nm and a laser spot size of 20 μm. [9]. 57 Fe Mössbauer at 80 K for Fe10Sn6A showed that the doublet observed at 298 K is a superposition of hematite with low size of crystallite and a paramagnetic Fe(III) phase (Fig.…”

Section: Characterizationmentioning

confidence: 99%

Effect of Sn on methane decomposition over Fe supported catalysts to produce carbon

et al. 2011

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In this work, alumina-supported Sn containing Fe catalysts were investigated in CVD reactions (Chemical Vapor Deposition) using methane for carbon production. The catalysts were prepared with 10 wt.% of Fe (as Fe 2 O 3 ) and 3, 6 and 12 wt.% of Sn (as SnO 2 ) supported on Al 2 O 3 named hereon Fe10Sn3A, Fe5Sn6A and Fe10Sn12A, respectively. These catalysts were characterized by SEM, TPCVD, TPR, TG, Raman, XRD and 57 Fe and 119 Sn Mössbauer spectroscopy. Methane reacts with Fe10A catalyst (without Sn) in the temperature range 680-900 • C to produce mainly Fe 0 , Fe 3 C and 20 wt.% of carbon deposition. TPR and TPCVD clearly showed that Sn strongly hinders the CH 4 reaction over Fe catalyst. 57 Fe Mössbauer suggested that in the presence of Sn the reduction of Fe +3 by methane becomes very difficult. 119 Sn Mössbauer showed Sn +4 species strongly interact with metallic iron after CVD, producing iron-tin phases such as Fe 3 SnC and FeSn 2 . This interaction Sn-Fe increases the CVD temperatures and decreases the carbon yield leading to the production of more organized forms of carbon such as carbon nanotubes, nanofibers and graphite.

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Influence of Sn4+ and Sn4+/Mg2+ doping on structural features and visible absorption properties of α-Fe2O3 hematite

Cited by 45 publications

References 27 publications

Hematite Surface Activation by Chemical Addition of Tin Oxide Layer

Hematite Surface Activation by Chemical Addition of Tin Oxide Layer

Review of Sn‐Doped Hematite Nanostructures for Photoelectrochemical Water Splitting

Effect of Sn on methane decomposition over Fe supported catalysts to produce carbon

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