Towards highly efficient photoanodes: boosting sunlight-driven semiconductor nanomaterials for water oxidation

Gan, Jiayong; Lu, Xihong; Tong, Yexiang

doi:10.1039/c4nr01181c

Cited by 179 publications

(130 citation statements)

References 122 publications

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“…The highest photocurrent density obtained here, 12 μA/cm 2 , is comparable with or higher than previously reported values for N-doped Nb 2 O 5 measured under similar conditions: 13 μA/cm 2 in the case of planar films (at 0.5 V versus Ag/AgCl) [30] and 7 μA/cm 2 for material prepared in the ordered mesoporous form (at 1.2 V versus Ag/AgCl). [31] Though not yet competitive with materials such as BiVO 4 and WO 3 , for which current densities of order of 0.5 mA/cm 2 have been reported, [32] this study reveals the tunability of properties afforded by control of the microcone growth conditions.…”

Section: Resultsmentioning

confidence: 94%

Rapid and controlled electrochemical synthesis of crystalline niobium oxide microcones

et al. 2015

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We demonstrate the fabrication by anodization of niobium oxide microcones, several microns long, from aqueous solutions of 1 wt% hydrogen fluoride (HF) with varied sodium fluoride (NaF) concentration (0-1 M). Raman spectroscopy and x-ray diffractometer analysis revealed the as-grown microcones to be crystalline Nb 2 O 5−x with preferred (1 0 0) and (0 1 0) orientations. The overall Nb 2 O 5−x formation rate increased with the increasing NaF concentration, and structures as tall as 20 μm were achieved in just 20 min of anodization at 1 M NaF. Rapid formation of niobia microcones was even observed in the absence of HF at this NaF concentration. Photocatalytic activity for water oxidation was highest for microcones grown under the highest NaF concentration.

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Section: Resultsmentioning

confidence: 94%

Rapid and controlled electrochemical synthesis of crystalline niobium oxide microcones

et al. 2015

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“…Among the different materials already tested, 9 TiO 2 and Fe 2 O 3 have attracted a lot of attention in PEC water splitting applications, since they fulfill several of these requirements. [10][11][12] TiO 2 has been the first material tested for water oxidation.…”

Section: Introductionmentioning

confidence: 99%

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

et al. 2016

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We discuss here for the first time how to combine iron and titanium metal ions to achieve a high photo-electrochemical activity for TiO 2 -based photo-anodes in water splitting devices. To do so, a wide range of photoelectrode materials with tailored Ti/Fe ratio and element vicinity were synthesized by using the versatility of aqueous sol-gel chemistry in combination with a microwave-assisted crystallization process. At low ferric concentrations, single phase TiO 2 anatase doped with various Fe amounts were prepared. Strikingly, at higher ferric concentrations, propose that the nature of the heterojunction impacts charge carrier recombination. The results presented herein not only answer whether iron and titanium should be combined in the same structure or into heterostructured systems, but also on the importance of the arrangement of ions in the structure to improve the performances of the photoanode.

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“…[1][2][3][4][5][6][7][8][9] Among inorganic materials that catalyze the photoelectrolysis of water, WO 3 with a bandgap of 2.6 eV is attractive due to its visible absorption and its photochemical stability in acid aqueous solution up to pH 5. [10][11][12][13] Since it was first reported as a potential photoanode for photoelectrochemical cells (PEC) in 1976, 14 many aspects of WO 3 including synthesis, 15 crystal structures, 10 as well as its electrochromic phenomena 16 have been extensively studied.…”

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confidence: 99%

Enhancing Majority Carrier Transport in WO₃Water Oxidation Photoanode via Electrochemical Doping

Zhao

Olide

Osterloh

2014

J. Electrochem. Soc.

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Here we report an electrochemical reduction-induced photocurrent enhancement up to an order of magnitude for monoclinic tungsten trioxide (WO 3 ) particulate photoanodes. Electrochemical impedance and photoelectrochemical measurements suggest that the improved performance is attributed to the increase in majority carrier concentration (from 1.5 × 10 18 to 2.5 × 10 21 cm −3 ). This results in higher conductivity and improved electron transport. Minority carrier extraction can be increased by reducing the WO 3 particle size from 200 nm to 50 and 30 nm. The larger solid-liquid interface area promotes the water oxidation rate. By balancing electron/hole extraction with photon absorption in an optimized 30 nm WO 3 particulate electrode, a record water oxidation photocurrent of 3.8 mA/cm 2 , under +1.36 V (vs. RHE) applied bias in 0.1 M Na 2 SO 4 solution at pH = 3.5 is achieved with 50 mW/cm 2 unfiltered Xe illumination. Photoelectrochemical water splitting is an efficient way of converting solar energy to chemical fuel by decomposing water into hydrogen and oxygen.1-9 Among inorganic materials that catalyze the photoelectrolysis of water, WO 3 with a bandgap of 2.6 eV is attractive due to its visible absorption and its photochemical stability in acid aqueous solution up to pH 5. [10][11][12][13] Since it was first reported as a potential photoanode for photoelectrochemical cells (PEC) 27-32 and enhancing WO 3 stability in neutral solution using surface coating. 27 Recently, Yat Li's group reported that a hydrogen treatment at 350• C of hydrothermally synthesized WO 3 films enhanced photoactivity and photostability of the WO 3 electrode, due to the incorporation of W 5+ donors and oxygen vacancies. 24 The W 5+ states are believed to be more resistant to photocorrosion by peroxo-intermediates formed during water oxidation and they improve electron transport in the WO 3 films. Herein, we demonstrate that a similar performance increase can be achieved by in-situ electrochemical reduction of WO 3 particle films at +0.17 V vs. RHE (−0.04 V vs. NHE) in aqueous electrolyte. The reduction increases the water oxidation photocurrent of WO 3 by over an order of magnitude, up to 3.8 mA/cm 2 for an optimized device. This is comparable to the highest observed water oxidation photocurrents for WO 3 films reported in the literature (>2.5 mA cm −2 , AM 1.5, E App = 1.0 V vs. NHE). 18,23,[33][34][35][36] Furthermore, this photocurrent enhancement is achieved without the utilization of sophisticated film geometry design 18 or water oxidation electrocatalysts. [27][28][29][30][31] The relative photocurrent enhancement is most pronounced for films composed of bulk WO 3 particles (enhancement factor of 14 fold), followed by films of 50 nm particles (10 fold) and 30 nm particles (2 fold). The reduction treatment also improves the stability of WO 3 against photocorrosion; after reduction, 50% of the photocurrent persists after 1 hr operation, compared to 10% for an untreated film. The enhancement is preserved in air, when films are at roo...

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Towards highly efficient photoanodes: boosting sunlight-driven semiconductor nanomaterials for water oxidation

Cited by 179 publications

References 122 publications

Rapid and controlled electrochemical synthesis of crystalline niobium oxide microcones

Rapid and controlled electrochemical synthesis of crystalline niobium oxide microcones

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

Enhancing Majority Carrier Transport in WO₃Water Oxidation Photoanode via Electrochemical Doping

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Towards highly efficient photoanodes: boosting sunlight-driven semiconductor nanomaterials for water oxidation

Cited by 179 publications

References 122 publications

Rapid and controlled electrochemical synthesis of crystalline niobium oxide microcones

Rapid and controlled electrochemical synthesis of crystalline niobium oxide microcones

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

Enhancing Majority Carrier Transport in WO3Water Oxidation Photoanode via Electrochemical Doping

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Enhancing Majority Carrier Transport in WO₃Water Oxidation Photoanode via Electrochemical Doping