Sn-doped Hematite Research Articles

(Invited) Highly Nanoporous Hematite with Optimal Doping for an Efficient Photoelectrochemical Water Splitting

In this study, we propose a highly nanoporous hematite structure having under 5 nm hole diffusion pathways via an optimized doping method based on Density Functional Theory (DFT) calculations. The superiority of highly nanoporous structure with the synergistic effects of a facilitated Kirkendall effect and optimal doping condition were clearly proved by the experimental analyses. The optimized prous photoanode prepared with an optimal doping conditoin (Ge:Ti:Sn doped hematite) and the subsequent dopositon of an oxygen evolution reaction co-catalyst NiFe(OH)x showed a maximum photocurrent density of 5.1 mA cm-2 at 1.23 VRHE, which is 3.3-fold higher than that of reference Ti:Sn hematite due to enhanced surface reaction kinetics. This study provides a significant breakthrough in dramatically improving the low PEC performance of hematite-based photoanodes with an short-hole diffusion pathway issue through optimal co-doping and nanostructuring.

Improved photoelectrochemical water splitting performance of Sn-doped hematite photoanode with an amorphous cobalt oxide layer

Hematite with a suitable band gap is a promising candidate as the photoanode for photoelectrochemical water splitting, but it suffers from low catalytic activity and severe electron-hole recombination. Herein, a novel two-step solvothermal synthetic strategy is developed to fabricate a uniform CoOx amorphous layer with a thickness of 5 nm on Sn-doped Fe2O3 nanowire photoanode. The CoOx surface layer increases the roughness of the photoanode significantly, and thus enlarges the electrochemical active area. Furthermore, the CoOx layer brings Co2+/Co3+ redox couples, enhances the concentration of oxygen vacancies and increases the charge carrier density. The bulk and surface charge separation efficiencies are both improved. The surface charge transfer process and the oxygen evolution reaction are accelerated. The photocurrent density of the Sn–Fe2O3 photoanode at 1.23 V (vs. reversible hydrogen electrode) is improved from 0.83 to 1.40 mA cm−2 after the deposition of the CoOx surface layer.

Sn-Doped Hematite Films as Photoanodes for Photoelectrochemical Alcohol Oxidation

Here, the modification of semiconductor thin film hematite photoanode by doping with Sn ions is reported. Undoped and Sn-doped hematite films are fabricated by the electrochemical deposition of FeOOH from aqueous alkaline electrolyte, followed by calcination in air. The photoanodes were tested in photoelectrocatalytic oxidation of water, methanol, ethylene glycol, and glycerol. It is shown that modification by tin dramatically increased the activity of hematite in the photoelectrochemical oxidation of alcohols upon visible light irradiation. The photoelectrocatalytic activity of Sn-modified hematite increased in the sequence of: H2O < MeOH < C2H2(OH)2 < C3H5(OH)3. The quantum yield of photocurrent in the oxidation of alcohols reached 10%. The relatively low photocurrent yield was ascribed to the recombination of photoexcited holes within the hematite layer and on surface states located at the hematite/electrolyte interface. Intensity-modulated photocurrent spectroscopy (IMPS) was used to quantify the recombination losses of holes via surface states. The IMPS results suggested that the hole acceptor in the electrolyte (alcohol) influences photocurrent both by changing the charge transfer rate in the photoelectrooxidation process and by the efficient suppression of the surface recombination of generated holes. Thin-film Sn-modified hematite photoanodes are promising instruments for the photoelectrochemical degradation of organic pollutants.

One-step hydrothermal synthesis of Sn-doped α-Fe2O3 nanoparticles for enhanced photocatalytic degradation of Congo red

We report on the synthesis of Sn-doped hematite nanoparticles (Sn-α-Fe2O3 NPs) by the hydrothermal method. The prepared Sn-α-Fe2O3 NPs had a highly pure and well crystalline rhombohedral phase with an average particle size of 41.4 nm. The optical properties of as-synthesized α-Fe2O3 NPs show a higher bandgap energy (2.40–2.57 eV) than that of pure bulk α-Fe2O3 (2.1 eV). By doping Sn into α-Fe2O3 NPs, the Sn-doped hematite was observed a redshift toward a long wavelength with increasing Sn concentration from 0% to 4.0%. The photocatalytic activity of Sn-doped α-Fe2O3 NPs was evaluated by Congo red (CR) dye degradation. The degradation efficiency of CR dye using Sn-α-Fe2O3 NPs catalyst is higher than that of pure α-Fe2O3 NPs. The highest degradation efficiency of CR dye was 97.8% using 2.5% Sn-doped α-Fe2O3 NPs catalyst under visible-light irradiation. These results suggest that the synthesized Sn-doped α-Fe2O3 nanoparticles might be a suitable approach to develop a photocatalytic degradation of toxic inorganic dye in wastewater.

Sn doped Hematite Nanorods for High-Performance Photoelectrochemical Water Splitting

Photoelectrochemical water splitting is of great attention due to its environmentally friendly generation of clean fuels. Hematite (α-Fe2O3) is considered a promising candidate due to its intrinsic properties for the high-performance photoelectrochemical electrode, such as favorable bandgap (2.0–2.2 eV), a suitable energy band position non-toxicity, low cost, and excellent chemical stability. Herein, we report about Sn-doped hematite nanorods and their implementation as photoanodes for photoelectrochemical water splitting. We provide the simple but efficient route to incorporate the Sn into the hematite without structural damage in the nanostructure and scrutinize the effect of Sn dopant on the photoelectrochemical activity of the hematite. Sn can be successfully incorporated into the hematite by the two-step heat treatment process, which reveals the enhanced photoelectrochemical responses compared with undoped hematite. We elaborate on the effect of Sn dopant in the hematite on the photoelectrochemical activities, thereby suggesting the optimum concentration of Sn dopant.

Influence of Sn doping on the structural, magnetic, optical and photocatalytic properties of hematite (α-Fe2O3) nanoparticles

Sn-doped hematite (α-Fe2O3) nanoparticles of fairly uniform and Sn-dependent size and shape were synthesized via a simple combination of hydrothermal co-precipitation and calcination. The effects of Sn doping on the unit cell size, crystallinity, particle size and shape, as well as the magnetic, optical and photocatalytic properties of hematite nanoparticles were analyzed. The incorporation of Sn4+ ions into the crystal structure of hematite was confirmed by determination of the unit cell expansion due to the replacement of octahedrally coordinated Fe3+ ions by significantly larger Sn4+ ions, as well as a substantially reduced hyperfine magnetic field due to magnetic dilution upon the substitution of non-magnetic Sn4+ ions for magnetic high-spin Fe3+ ions. Sn doping caused a decrease in length and width and an increase in thickness of elongated hematite nanoparticles. Fairly uniform Sn-doped hematite nanoellipsoids or nanocuboids were formed, depending on the Sn content. Temperature dependence of magnetization measurements showed the disappearance of the magnetic phase transition (Morin transition) in hematite upon Sn doping. Magnetic coercivity decreased upon Sn doping due to a decrease in shape anisotropy induced by the change in particle shape from nanorods to nanoellipsoids and nanocuboids. The optical and electronic properties of hematite nanoparticles were significantly affected by Sn doping – the absorption edge was shifted to higher wavelengths, while direct and indirect optical band gaps narrowed with the increasing Sn4+-for-Fe3+ substitution. Sn-doped hematite nanoellipsoids containing 4.3 mol% Sn exhibited a substantial visible light photocatalytic activity in the heterogeneous photo-Fenton process, but this activity significantly decreased with higher Sn doping.

Fabrication of tin‐doped hematite modified with NiFe‐LDH nanoflakes for highly efficient solar water splitting

Photoelectrochemical (PEC) water splitting is widely regarded as an effective process for sustainable storage of solar energy as chemical energy in the form of H2. The efficiency of this process depends upon the light absorption, charge injection, and charge separation efficiency of the photoanode material used. In this work, doping hematite with 1% tin and loading with NiFe-layered double hydroxide (LDH) co-catalyst has been done to improve the charge transport properties. To enhance the PEC performance and study the effect of precursor concentration, NiFe-LDH at two different concentrations (low and high) was coated on Sn-doped hematite. A high photocurrent density ca. 2.9 mA/cm2 at 1.8 V vs reversible hydrogen electrode (RHE) and a 170 mV cathodic shift in onset potential compared to pristine hematite (0.22 mA/cm2 at 1.8 V vs RHE) was recorded for Sn-doped hematite coated with low precursor concentration. The enhanced PEC activity can be attributed to the synergistic effect of Sn doping and NiFe-LDH co-catalyst on hematite, which contributes to an efficient separation of the photogenerated charge carriers and reduces hole accumulation at the surface. However, for the high precursor concentration case, the formation of a thick film of NiFe-LDH results in a comparatively lower current density (0.85 mA/cm2 at 1.8 V vs RHE). The results obtained show that NiFe-LDH can be used as an effective co-catalyst to significantly enhance the charge transport properties of tin-doped hematite. A charge transfer mechanism of the developed photoanodes is also discussed in detail.

Fe2O3 photoanodes: Photocorrosion protection by thin SnO2 and TiO2 films

The possibility of protection of Fe2O3 (hematite) against photocorrosion in aqueous electrolytes by thin layers of TiO2 and SnO2 deposited by ALD (atomic layer deposition), was investigated. Sn-doped hematite layers, as obtained in this study by aerosol pyrolysis had significant roughness and porosity. ALD is very successful in applying conformal films to such structures. The nominal coverage by ALD films was varied between 0.5 and 7.5 nm. The presence of the TiO2 and SnO2 films was evidenced by XPS. Photocurrents were strongly diminished as the capping layer thickness was increased. The Faradaic efficiency, f, of photocorrosion in acidic media (0.01 M H2SO4) was decreased from 0.026 to 0.014 and to 0.010 by capping with either a 2 nm thick overlayer of TiO2 or of SnO2, respectively. The latter had also a positive influence on the long term photocurrent stability.

Direct growth of hematite film on p+n-silicon micro-pyramid arrays for low-bias water splitting

Solar water splitting based on photoelectrochemical (PEC) cells has been intensively demonstrated to be promising for hydrogen energy, but it is usually difficult for one pure PEC system to achieve overall solar-driven water splitting. To solve this problem, integrating one PEC cell with one photovoltaic (PV) cell is widely employed, however, the preparation of an unabridged PV cell and the electrical connection between them are complicated. Herein, we directly synthesized hematite (α-Fe2O3) film on the as-prepared p+n-Si micro-pyramid arrays with the modifications of SnO2 interlayer and Co-Pi catalyst overlayer, and the turn-on potential achieved a substantial decrease, which is 0.34 V smaller than the Sn-doped hematite film grown on the FTO substrate (FTO/Sn@α-Fe2O3). The influences of interlayer, overlayer and α-Fe2O3 preparation conditions are systemically investigated. Besides, we comparatively studied the FTO/Sn@α-Fe2O3 photoanode in tandem with the complete p+n-Si micro-pyramid PV cell, and observed the turn-on potential as low as 0.32 V vs. RHE. The performance improvement is ascribed to a combination of the additional photovoltage from the embedded p+n-Si junction, the enhancement both in optical absorption and surface area of α-Fe2O3 film, and the promoted collection efficiency of photogenerated carriers from the interface and surface modifications. This work fills the gap of combining α-Fe2O3 photoanode and p+n-Si junction with the aim of overall solar-driven water splitting, and provides a new route to simplify the PEC/PV tandem system.

Au@SiO2@Au core-shell-shell nanoparticles for enhancing photocatalytic activity of hematite

Photoelectrochemical (PEC) water splitting for hydrogen generation using abundantly available solar energy is a promising strategy toward developing a carbon-neutral society. Here, we demonstrate the first use of Au@SiO2@Au core-shell-shell (CSS) plasmonic nanoparticles (NPs) for improvement of the photocatalytic performance in PEC photoanodes using hematite as a testing system. Using rigorous calculations based on the Mie scattering theory on CSS NPs, we have designed and optimized the dimensions of each layer in the CSS NPs for the double resonance peaks of the CSS NPs with maximal contribution to the enhancement of the hematite PEC activity. Two different NP/hematite architectures on synthesized Sn-doped hematite nanocoral films have been studied – a top-deposited configuration with the optimized CSS NPs on the surface of the hematite, and an embedded configuration with the hematite nanocorals grown over the optimized CSS NPs. Compared with the bare hematite, the average photocurrent density, as a measure of the PEC activity, was found to be improved by 0.6 mA/cm2 and 1.45 mA/cm2 for the top-deposited and embedded CSS NP/hematite configurations, respectively. In particular, the best embedded sample showed an improvement in the photocurrent density from 0.82 mA/cm2 for the bare hematite to 3.0 mA/cm2. This improvement of 2.18 mA/cm2 is one of the highest improvements gained from a plasmonic enhancement strategy for a hematite photoelectrocatalytic system. In addition, the CSS NPs outperformed Au NPs by 1.67 times in the top-deposited configuration and up to 8 times in the embedded configuration. Our simulation and experiment results showed the following key features of CSS NPs which are critical for improving the photocurrent of hematite: (1) a double resonance peak, each of which can contribute separately to the photocurrent, (2) easy tunability of the peaks by varying the dimensions of the CSS NPs and subsequently making the plasmonic peaks strongly scattering or strongly absorbing, thereby optimizing the contributions to the PEC activity of hematite, and (3) spatially uniform electric field distributions which extend 20–25 nm from the outer surface and hence offer potential of increasing carrier generation. Our results show CSS NPs as new and improved plasmonic systems for enhancing PEC performance.

Theoretical analysis of an intermediate band in Sn-doped hematite with wide-spectrum solar response

Hematite α-Fe2O3 is exposed to be an efficient photocatalytic material for the photoelectrochemical water splitting process under visible light. In the present work, we have improved the photocatalytic activity of hematite by varying tin concentration substituted for Fe in pristine hematite. To investigate the influence of the contents of Sn on the photocatalytic activity, various key properties like electronic structure and optoelectronic properties were studied based on density functional theory using generalized gradient approximation plus on-site Hubbard interaction within the WIEN2k computer program. The results of the electronic band structure show the insulating character of the pristine hematite exhibits a bandgap of 2.17 eV equals to Exp. one. The electronic structure calculations of the Sn-doped hematite explore the engineering of the orbitals around the Fermi level and result in a reduction in the bandgap, which is attributed to the corresponding Sn contents. The doping of Sn in Fe2O3 would introduce sub-bands (intermediate band) in between the valence band maximum (VBM) and Fermi level EF, and more interestingly, half-filled intermediate bands appear around the Fermi level with the increase of Sn contents. To see the effect of intermediate bands on the optoelectronic features of the Sn-doped hematite, we also calculated the optical properties of pristine and doped hematite, which predict extra peaks assigned to transitions of electrons from intermediate bands in the infrared region. Our findings explore that the presence of intermediate bands facilitates the PEC activity of water splitting of Fe2O3, shifting from visible light to infrared region. Here, we demonstrate the idea of intermediate bands in hematite for distinctive device applications.

Sn-Doped Hematite Nanoparticles for Potential Photocatalytic Dye Degradation

Recently, low-cost hematite (α-Fe2O3) metal oxide semiconductor has attracted enormous attention for the photoelectrochemical water splitting and photocatalytic applications. The main purpose of this work is to study the effects of Sn-doping on the photocatalytic properties of hematite nanoparticles (NPs). Morphology and physicochemical properties of prepared samples were analyzed using X-ray diffraction analysis (XRD), transmission electron microscope (TEM), and UV-vis spectroscopy. Rhodamine B (RB) dye was used as a model organic pollutant to test the photocatalytic activity of prepared samples. It was found that the photocatalytic activity of Sn-doped hematite NPs was higher than that of the undoped hematite NPs. The recyclability tests suggested that 3 mol% Sn-doped hematite NPs can be used as a promising reusable photocatalyst for dyes degradation.

Underlayer engineering into the Sn-doped hematite photoanode for facilitating carrier extraction.

A semiconductor underlayer(s) has been extensively used to improve the performance of photoelectrochemical (PEC) cells. Unfortunately, in many cases, the incorporation of underlayers leads to degraded system performances. A comprehensive study on the functions and manipulations of underlayers is therefore of high significance for achieving high-performance PEC cells. This study indicates that Sn-doped hematite photoanodes decorated with various underlayer materials show substantially distinguished photocurrent responses, leading to qualitatively different PEC cells. With an optimized TiO2 (ITO, Al2O3) underlayer, the photocurrent density at 1.23 V versus RHE can be enhanced from 0.25 to 0.71 (0.59, 0.42) mA cm-2, while it is decreased to 0.14 mA cm-2 by using NiO. Our further analysis reveals that the performance differences come mainly from the distinguished bulk and surface carrier recombination effects, i.e., (1) metal doping (i.e., Ti4+, In3+ and Al3+) from the underlayers improves the conductivity of hematite film and thus reduces the bulk recombination; (2) the underlayers of TiO2, ITO and Al2O3 can effectively suppress the carrier recombination at the bottom/top surfaces of the hematite layer, while the NiO underlayer leads to a higher surface recombination. Our work provides a basis for selecting an underlayer and a general guideline for the interface engineering for high performance photoelectrodes.

Structural, opto-electronic and photoelectrochemical properties of tin doped hematite nanoparticles for water splitting

For application in photoelectrochemical water splitting, pristine and Sn doped (1%, 3% and 5%) hematite nanoparticles were prepared hydrothermally via a two step heating process. XRD results showed that the products match the rhombohedral crystal system. The peak broadening of hematite nanoparticles due to small crystallite size and strain were analyzed by Scherrer's equation and Williamson Hall plot method respectively. A decrease in crystallite size and an increase in lattice strain is observed with dopant addition. Structural change from nanorods to nanocorals is seen for the Sn doped hematite products. Selected Area Diffraction patterns reveal crystallinity of both the doped and undoped powders. Sn 3d XPS peak analysis reveals that Sn has been doped into the hematite lattice. Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy analysis confirm that 1% Sn doped hematite has the highest photocurrent density (3 mA/cm2 at 1 V vs. Ag/AgCl) and least charge transfer resistance among the doped products. UV-VIS, Photoluminescence and Mott-Schottky analysis further show that optimum optical and electrical properties are observed for hematite doped with 1% Sn.

Sn-Doped Hematite for Photoelectrochemical Water Splitting: The Effect of Sn Concentration

Abstract Hematite-based photoanodes have been intensively studied for photoelectrochemical water oxidation. The n-type dopant Sn has been shown to benefit the activity of hematite anodes. We demonstrate in this study that Sn-doped hematite thin films grown by atomic layer deposition can achieve uniform doping across the film thickness up to at least 32 mol%, far exceeding the equilibrium solubility limit of less than 1 mol%. On the other hand, with the introduction of Sn doping, the hematite crystallite size decreases and many twin boundaries form in the film, which may contribute to the low photocurrent observed in these films. Density functional theory calculations with a Hubbard U term show that Sn doping has multiple effects on the hematite properties. With increasing Sn4+ content, the Fe2+ concentration increases, leading to a reduction of the band gap and finally to a metallic state. This goes hand in hand with an increase of the lattice constant.

α-Fe2O3 nanorods embedded with two-dimensional {0 0 1} facets exposed TiO2 flakes derived from Ti3C2TX MXene for enhanced photoelectrochemical water oxidation

The Sn-doped α-Fe2O3 nanorods were embedded with {0 0 1} facets exposed TiO2 flakes by a facile hydrothermal synthesis and post-calcination treatment (denoted as E-Sn-Fe2O3/TiO2). The {0 0 1} facets exposed TiO2 flakes were derived from the delaminated Ti3C2TX MXene (D-Ti3C2TX) without adding extra HF or F ions during hydrothermal synthesis because the surface of D-Ti3C2TX was natively terminated by –F functional groups. The Sn-doped hematite/surface-covered TiO2 (denoted as S-Sn-Fe2O3/TiO2) and Sn-doped hematite (denoted as Sn-Fe2O3) were also fabricated for comparison. Under simulated sunlight, the E-Sn-Fe2O3/TiO2 yielded a photocurrent density of 0.85 mA cm−2 at 1.23 V (vs. RHE) compared with 0.72 mA cm−2 and 0.42 mA cm−2 for S-Sn-Fe2O3/TiO2 and Sn-Fe2O3, respectively. The E-Sn-Fe2O3/TiO2 achieved an IPCE value of 18.6% at 380 nm (15.8% for S-Sn-Fe2O3/TiO2 and 10.4% for Sn-Fe2O3) and exhibited enhanced IPCE values at all measured wavelengths compared with the other two photoanodes. The unique architecture of embedded TiO2 can improve the interfacial contact between the α-Fe2O3 and TiO2 as well as the light harvesting of the α-Fe2O3 compared with the surface-covered TiO2, which contributes to the better charge-transport ability and enhanced PEC performance. The exposed {0 0 1} facets of TiO2 in the E-Sn-Fe2O3/TiO2 photoanode may also facilitate the charge transfer and improve the PEC performance.

Hematite films by aerosol pyrolysis: Influence of substrate and photocorrosion suppression by TiO2 capping

Sn-doped hematite (Fe2O3) films were prepared by aerosol pyrolysis (AP) on fluorine doped tin oxide (FTO), titanium and stainless steel. Photoactive electrodes were obtained in all cases and the photosensitivity had an onset around 650 nm. Maximum incident photon to electron conversion efficiency (IPCE) was 0.3 at 300 nm for samples deposited on FTO. The Faradaic efficiency of the photocorrosion reaction was found to be 0.47% for an unprotected FTO/hematite electrode in H2SO4. The Faradaic efficiency of this dissolution reaction decreased to 0.3% for a hematite electrode covered with a 65 nm thick dip coated layer of TiO2, and to 0.17% for a sample with a spray coated TiO2 layer, thus proving the beneficial role of TiO2 in protecting hematite against photocorrosion.

Tubular morphology preservation and doping engineering of Sn/P-codoped hematite for photoelectrochemical water oxidation.

Tubular hematite with high-concentration, uniform doping is regarded as a promising material for photoelectrochemical water oxidation. However, the high-temperature annealing commonly used for activating doped hematite inevitably causes deformation of the tubular structure and an increase in the trap states. In the present work, Sn-doped tubular hematite on fluorine-doped tin oxide (FTO) is successfully obtained at 750 °C from a Sn-coated FeOOH tube precursor. Sn/P codoping, which is rarely considered for hematite, is also achieved via a gas phase reaction in phosphide atmosphere. The tubular morphology allows the dopant to diffuse from both the inner and outer surfaces, thus decreasing the doping profile in the radial direction. The even distribution of Sn and P synergetically increases the carrier density of hematite by one order of magnitude, which shortens the width of the depletion layer to ca. 2.3 nm (compared with 19.3 nm for the pristine sample) and leads to prolonged carrier lifetime and efficient charge separation. In addition, this codoping protocol does not introduce additional surface trap states, as evidenced by the increased charge injection efficiency and surface kinetic analysis using intensity modulated photocurrent spectroscopy (IMPS). As a result, the morphology- and doping-engineered hematite exhibits photocurrents of 0.9 mA cm-2 at 1.23 V and 3.8 mA cm-2 at 2.0 V vs. RHE under AM 1.5 G illumination (100 mW cm-2) in 1.0 M NaOH, representing 4.5-fold and 4.8-fold enhancements, respectively, compared with the photocurrents of undoped hematite. The present method is shown to be effective for preparing multi-element-doped hematite nanotubes and may find broad application in the development of other nanotubular photoelectrodes with or without doping for efficient and robust water oxidation.

Sn Doping into Hematite Nanorods for High-Performance Photoelectrochemical Water Splitting

Photoelectrochemical water splitting is of great attention due to its environmental friendly generation of clean fuels. Hematite (α-Fe2O3) is considered one of the promising candidates due to its intrinsic properties for the high performance photoelectrochemical electrode such as favourable bandgap (2.0–2.2 eV), a suitable energy band position, non-toxicity, low cost, and excellent chemical stability. Herein, we report about Sn-doped hematite nanorods and their implementation as photoanodes for photoelectrochemical water splitting. We provide the simple but efficient route to incorporate the Sn into the hematite without structural damage in the nanostructure and scrutinize the effect of Sn dopant on the photoelectrochemical activity of the hematite. By the two-step heat-treatment process, Sn can be successfully incorporated into the hematite, which reveals the enhanced photoelectrochemical responses compared with undoped hematite. We elaborate the effect of Sn dopant in the hematite on the photoelectrochemical activities, thereby the optimum concentration of Sn dopant can be suggested. In addition, the catalyst layer of the cobalt phosphate is introduced to further increase the photoelectrochemical performance of Sn-doped hematite nanorods.

Introduction of oxygen vacancies into hematite in local reducing atmosphere for solar water oxidation

Sn Doping and creation of oxygen vacancies have been adopted universally to overcome the poor electric conductivity and unfavorable hole diffusion length of α-Fe2O3 photoanodes. Generally, Sn doping is realized via longitudinal migration of tin element from FTO (fluorine-doped tin oxide) substrates into α-Fe2O3 at high temperature. To introduce oxygen vacancies along with Sn into hematite for further promoting its electric conductivity, we have created a local reducing atmosphere via partial oxidation of graphite while doping hematite with Sn. The donor density of the resultant Fe2O3 photoanode annealed on graphite (G-Fe2O3) at 770 °C for 20 min is increased to ∼1.7 times that of the counterpart annealed on SiO2 powders (S-Fe2O3), indicating that the electric conductivity of hematite is improved after introduction of oxygen vacancies. Moreover, oxygen vacancies have been demonstrated to significantly reduce the charge transfer resistance of Sn doped hematite. Consequently, the photocurrent density of G-Fe2O3 is enhanced remarkably (∼70%) compared with S-Fe2O3. However, the improvement in photocurrent density due to oxygen vacancies becomes less significant when more Sn is doped into hematite. The strategy for creation of oxygen vacancies reported here can be extended to other photoanodes for better understanding the effect of oxygen vacancies on PEC performance.