Hydrothermal Synthesis of Hematite Nanoparticles and Their Electrochemical Properties

Zhu, Maiyong; Wang, Ying; Meng, Dehai; Qin, Xingzhang; Diao, Guowang

doi:10.1021/jp304041m

Cited by 227 publications

(145 citation statements)

References 65 publications

Supporting

Mentioning

139

Contrasting

Order By: Relevance

“…The relative large pores allow the good penetration of electrolyte in the electrode materials, ensuring the good wettability of the electrode 6b shows the galvanostatic discharge curves at different current densities. Two plateaus are clearly observed on the discharge curve, which can be explained by the two-step reduction process [21]. The result is in good accordance with the CV result.…”

Section: Resultssupporting

confidence: 85%

Multi-shelled α-Fe2O3 microspheres for high-rate supercapacitors

et al. 2016

View full text Add to dashboard Cite

Hollow structured metal oxides are extensively studied in energy storage and conversion systems. In this work, we report the fabrication of multi-shelled Fe2O3 microspheres with nanospindles assembly on its exterior shell. The β-FeOOH precursor nanospindles were firstly grown on the surface of carbon microspheres to produce β-FeOOH@carbon composites, which were later converted into multi-shelled Fe2O3 microspheres by calcination in air. As electrode material for supercapacitors, the multi-shelled Fe2O3 microspheres exhibit high capacity and good rate capability. The electrode delivers the specific capacitances of 630 and 510 F g −1 at the current densities of 1 and 5 A g −1 , respectively.

show abstract

Section: Resultssupporting

confidence: 85%

Multi-shelled α-Fe2O3 microspheres for high-rate supercapacitors

et al. 2016

View full text Add to dashboard Cite

show abstract

“…[27][28][29] In addition, previous studies have incorporated PVP in the hydrothermal synthesis of iron oxide from Fe 3+ salts, in which PVP acts as a surfactant or directing agent, promoting anisotropic growth oriented along specific crystal planes. [30][31][32] To our knowledge, anodic electrodeposition in the presence of PVP has not been previously reported, and we show here its incorporation leads to hematite photoanodes with significantly improved water oxidation photocurrent. We further find that annealing conditions can markedly affect electrode performance, with distinct effects for electrodes deposited with PVP versus without.…”

mentioning

confidence: 54%

Enhancement of Water Oxidation Photocurrent for Hematite Thin Films Electrodeposited with Polyvinylpyrrolidone

Ishaq

Sikora

Scheidler

et al. 2016

J. Electrochem. Soc.

View full text Add to dashboard Cite

Hematite photoanodes were prepared by anodic electrodeposition in the presence of polyvinylpyrrolidone (PVP). PVP has been shown to alter hematite nanoparticle morphology, but has not been used before for anodic electrodeposition of thin films. Significant improvement in the water oxidation photocurrent was observed with PVP, with greater charge-collection efficiency due to a finer nanostructured morphology, and higher quantum yields for photons absorbed throughout the thickness of the hematite film from its increased porosity. Different post-deposition treatments showed distinct effects with and without PVP. Compared to electrodes dried 48 hours before annealing under N 2 , electrode performance was significantly reduced upon annealing in air, or annealing immediately after deposition when PVP was not used. A distinct wavelength dependence for front-versus back-side illumination, and a ∼100-fold decrease in dopant density, was attributed to formation of a dead layer on the top of those electrodes with reduced photoactivity, and was avoided using PVP. The stability, abundance, and environmental compatibility of hematite (α-Fe 2 O 3 ) make it an attractive candidate for realizing the goal of directly generating hydrogen gas from water and sunlight with high efficiency and at low cost. Hematite is stable in all but acidic solutions, can absorb ∼40% of the solar spectrum, and has suitable band edge positions for water oxidation. However, its performance in photoelectrochemical (PEC) cells is plagued by its short holediffusion lengths. To overcome this, electrodes with nanostructured morphologies are commonly prepared to optimize photon absorption and charge-carrier collection.1-3 High aspect-ratio nanorods or other nanostructures allow for the orthogonalization of the absorption depth and charge-carrier-diffusion length, which is on the order of 2-10 nm for hematite. 4,5 In addition, modification of the surface with catalysts has been shown to reduce overpotentials by improving water oxidation kinetics and/or reducing surface recombination rates.1,6-10 Other studies have focused on doping hematite to alter charge-carrier densities, increase conductivity, and/or increase charge separation, transport, and collection efficiency. 2,3,[11][12][13][14][15] Although these efforts have led to impressive gains in performance, conversion efficiencies remain well below the theoretically predicted maximum value and many questions remain about how to maximize charge-carrier generation and collection, and how to optimize interfacial electron-transfer kinetics for the sluggish oxygen evolution reaction.Hematite thin films can be grown by a variety of methods, including atomic layer deposition, 7,15-17 hydrothermal precipitation, 3,18 spray pyrolysis, 19,20 chemical vapor deposition, 1,6,21 and electrodeposition, 22-26 among others. Electrodeposition provides a relatively simple, flexible, low-cost and easily scalable approach to synthesizing hematite. In this report, we focus on anodic electrodeposition to fabricate hematite phot...

show abstract

“…The hematite nanoparticles could be obtained by different routes: co-precipitation [20], microemulsion method [20,21], thermal decomposition [20,22], sol-gel method [23], ball milling [24], green synthesis method [25], sonochemical synthesis [26], forced hydrolysis [20,27,28], hydrothermal and solvothermal method [17,20,29].…”

Section: Introductionmentioning

confidence: 99%

“…Different iron sources for hematite nanoparticles are reported in literature: iron(III) chlorides (FeCl 2 and FeCl 3 ) [21,23,[27][28][29], ferrocene [22], iron(III) nitrate [17,25], ferrous sulfate [30], iron pentacarbonyl [26], etc.…”

Section: Introductionmentioning

confidence: 99%

Sonochemical Synthesis of Hematite Nanoparticles

Mihail¹

2015

ChemJMold

View full text Add to dashboard Cite

Abstract. Hematite nanoparticles were prepared by a procedure consisting in sonication of μ 3 -oxo trinuclear iron(III) acetate of composition [Fe 3 O(OOCCH 3 ) 6 (H 2 O) 3 ]NO 3 •4H 2 O, {Fe 3 O}NO 3 as iron source, in strong basic conditions followed by thermal treatment at 600˚C. The formation of the hematite was confi rmed by IR spectroscopy, X-ray powder diffraction and Raman spectroscopy while, the shape and size of the nanoparticles and their agglomeration were evidenced and estimated on the basis of the images taken with TEM techniques.Keywords: hematite, nanoparticles, iron oxides, sonochemistry. There are various forms of iron oxides [7]. They differ in composition, in the valence of Fe and, above all, in crystal structure. The most stable and wide spread oxide phase of iron is α-Fe 2 O 3 , where Fe has the lower Gibbs free energy [8]. Hematite has hexagonal structure of the corundum type with a close-packed oxygen lattice in which twothirds of the octahedral sites are occupied by Fe(III) ions. Bulk hematite is antiferromagnetic till Morin temperature (TM) (~260 K). Between TM and Neel temperature (TN) (~ 950K) it is weak ferromagnetic and above TN the hematite is paramagnetic [9,11]. These transitions are infl uenced by particle size, shape and crystallinity [9][10][11]. Particles smaller than 16 nm have a superparamagnetic behaviour at room temperature [12].Hematite nanoparticles proved to be effective catalyst in numerous reactions such as the decomposition of soot and NO x in diesel exhausts [13], oxidation of CO [14], photocatalytic degradation of salicylic acid [15], and FischerTropsch synthesis [16]. An iron-based solid catalyst is also normally used as a Lewis acid catalyst and/or support in homogeneous and heterogeneous catalysis [17]. Hematite nanoparticles could be applicable in water treatment technology for removing metal [18]. Hematite has a bandgap of 2-2.2 eV thus being semiconductor suitable for photocatalytic water-splitting with hydrogen formation [19].The hematite nanoparticles could be obtained by different routes: co-precipitation [20], microemulsion method [20,21], thermal decomposition [20,22] Our approach in this study is to obtain hematite nanoparticles using μ 3 -oxo homotrinuclear {Fe 3 O}NO 3 acetate as an iron source and easy sonochemical route as a synthesis procedure. The obtained product was characterized by adequate techniques (FTIR, energy-dispersive X-ray spectroscopy, Raman spectroscopy, wide angle X-ray spectroscopy, transmission electron microscopy), in order to evaluate the formed structure.

show abstract

Hydrothermal Synthesis of Hematite Nanoparticles and Their Electrochemical Properties

Cited by 227 publications

References 65 publications

Multi-shelled α-Fe2O3 microspheres for high-rate supercapacitors

Multi-shelled α-Fe2O3 microspheres for high-rate supercapacitors

Enhancement of Water Oxidation Photocurrent for Hematite Thin Films Electrodeposited with Polyvinylpyrrolidone

Sonochemical Synthesis of Hematite Nanoparticles

Contact Info

Product

Resources

About