Structure and oxidation state of hematite surfaces reacted with aqueous Fe(II) at acidic and neutral pH

Catalano, Jeffrey G.; Fenter, Paul; Park, Changyong; Zhang, Zhan; Rosso, Kevin M.

doi:10.1016/j.gca.2009.12.018

Cited by 80 publications

(77 citation statements)

References 66 publications

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“…review in [36]) which the authors interpreted as epitaxy. X-ray reflectivity measurements, however, demonstrated that extension of the hematite lattice was not perfect [37].…”

Section: Electron Transfer At Ferric (Hydr)oxides Surfaces: the Role mentioning

confidence: 92%

“…Handler et al [39] have established a mass balance for the isotope exchange between goethite and Fe(II) and assume enrichment of exchangeable Fe to occur in the surface region. These findings were refined in highlighting the role of crystal faces in growth and dissolution of hematite [37,40]. Sorption of Fe(II) occurs preferentially at the 001 face, while reductive dissolution at other faces.…”

Section: Electron Transfer At Ferric (Hydr)oxides Surfaces: the Role mentioning

confidence: 95%

See 1 more Smart Citation

Reductive Dissolution and Reactivity of Ferric (Hydr)oxides: New Insights and Implications for Environmental Redox Processes

Peiffer

Wan

2016

Iron Oxides

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“…review in [36]) which the authors interpreted as epitaxy. X-ray reflectivity measurements, however, demonstrated that extension of the hematite lattice was not perfect [37].…”

Section: Electron Transfer At Ferric (Hydr)oxides Surfaces: the Role mentioning

confidence: 92%

Section: Electron Transfer At Ferric (Hydr)oxides Surfaces: the Role mentioning

confidence: 95%

Reductive Dissolution and Reactivity of Ferric (Hydr)oxides: New Insights and Implications for Environmental Redox Processes

Peiffer

Wan

2016

Iron Oxides

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“…The forms of surface termination groups were assigned based on the results of surface characterization by XPS O 1s and FT-IR peak at 1200-1000 cm −1 , and some previous reports. [ 23,[25][26][27][28][29]39 ] As shown in Figure 5 , IEP was determined to be pH 8.3 for bare Fe 2 O 3 and pH 4.8 for Pi-Fe 2 O 3 , respectively. The pH 8.3 is in a good agreement with the reported IEP value for hematite (≈pH 8.5).…”

Section: A Stable and Effi Cient Hematite Photoanode In A Neutral Elementioning

confidence: 99%

A Stable and Efficient Hematite Photoanode in a Neutral Electrolyte for Solar Water Splitting: Towards Stability Engineering

Kim

Jang

Youn

et al. 2014

Advanced Energy Materials

118

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water splitting. So far, most studies employing hematite photoelectrodes were carried out in strongly basic conditions. [ 10,[14][15][16][17] It usually shows the poor performance (smaller water oxidation photocurrents and/or higher onset potential) and low stability in neutral electrolytes, although there is no systematic study on the effects of the electrolytes. In contrast, our modifi ed hematite photoanode showed almost the same performance in a neutral electrolyte at pH 7 as in a strongly basic electrolyte at pH 13.6. The modifi cation of the hematite photoanode was carried out by simply dipping the bare hematite thin fi lm in a solution containing phosphate ions and annealing it under mild conditions. The treatment led to the hematite thin fi lm being uniformly modifi ed with phosphate ions on its surface. The phosphate ions effectively prevent deterioration of performance in activity and stability in neutral electrolyte. There have been some reports of hematite photoanodes active for solar water splitting performed in neutral electrolytes, especially when the semiconductors are decorated by cobalt phosphate (Co-Pi) as an oxygen evolution reaction (OER) co-catalyst. [14][15][16][17][18][19] The Co-Pi works best in a phosphate buffer, yet the purpose and operating principle are distinguished from the present study as discussed later. Hence, this work represents the fi rst attempt at stability engineering by correlating surface electrostatic state of hematite and its performance and stability in electrolytes with different pH values.As described in the Experimental Section, the surface of the hematite photoanode was modifi ed by dipping the bare hematite thin fi lm in an aqueous sodium phosphate solution and annealing it under mild conditions. In the transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) mapping images shown in Figure 1 , phosphorus is uniformly distributed over the hematite surface as the hematite surface was successfully coated with phosphate ions. It was also confi rmed by scanning electron microscopy (SEM) and SEM-energy dispersive X-ray spectroscopy (EDS; Figure S1 of the Supporting Information). The surface morphology does not change after the surface modifi cation with phosphate ions, as shown in the SEM images of Figure S1 (Supporting Information). According to the EDS results, phosphorus certainly exists on the hematite surface treated with a solution containing phosphate ions. On the other hand, the bare hematite surface showed no phosphorus on the surface.To identify the chemical state of the surface species, X-ray photoelectron spectroscopy (XPS) analyses were carried out for the bare and the phosphate ion-modifi ed hematite thin fi lm (Pi-Fe 2 O 3 ). Figure 2 A shows a Fe 2p 3/2 peak at 711.2 eV, a 2p 1/2 peak at 724.4 eV, and a 2p 3/2 satellite peak at 719 eV, corresponding to binding energies of Fe 3+ . These features show

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“…The coexistence of Fe(II) and Fe(III), where Fe(II) generally occurs as the aqueous component and Fe(III) as the solid component, is common during weathering of Fe(II)-bearing primary crystalline rocks (Fantle and DePaolo, 2004), biological and abiotic oxidation of Fe(II)-rich fluids (e.g., groundwater seeps, mine drainage) (Frierdich et al, 2011a;Burgos et al, 2012;Roden et al, 2012), or during dissimilatory iron reduction (DIR) (Crosby et al, 2005(Crosby et al, , 2007Johnson et al, 2008). These processes may drive secondary, abiotic reactions between aqueous and sorbed Fe(II) and solid Fe(III) phases via Fe(II)-Fe(III) electron transfer and atom exchange (ETAE) (Williams and Scherer, 2004;Pedersen et al, 2005;Yanina and Rosso, 2008;Handler et al, 2009;Jones et al, 2009;Catalano et al, 2010;Rosso et al, 2010;Schaefer et al, 2010;Frierdich et al, 2011b;Neumann et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The effect of pH on stable iron isotope exchange and fractionation between aqueous Fe(II) and goethite

et al. 2015

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Structure and oxidation state of hematite surfaces reacted with aqueous Fe(II) at acidic and neutral pH

Cited by 80 publications

References 66 publications

Reductive Dissolution and Reactivity of Ferric (Hydr)oxides: New Insights and Implications for Environmental Redox Processes

Reductive Dissolution and Reactivity of Ferric (Hydr)oxides: New Insights and Implications for Environmental Redox Processes

A Stable and Efficient Hematite Photoanode in a Neutral Electrolyte for Solar Water Splitting: Towards Stability Engineering

The effect of pH on stable iron isotope exchange and fractionation between aqueous Fe(II) and goethite

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