A Co‐catalyst‐Loaded Ta<sub>3</sub>N<sub>5</sub> Photoanode with a High Solar Photocurrent for Water Splitting upon Facile Removal of the Surface Layer

Li, Mingxue; Luo, Wenjun; Cao, Dapeng; Zhao, Xin; Li, Zhaosheng; Yu, Tao; Zou, Zhigang

doi:10.1002/anie.201305350

Cited by 215 publications

(197 citation statements)

References 38 publications

(60 reference statements)

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“…After this long-term test, the action spectra were taken to calculate the QE; the results are shown in Figure 2 (and summarized in Table S1). The QE estimated between 400 and 680 nm correlates well with the estimated absorbance of the Ta3N5 samples (which agrees with previous reports (Figure S1)), [7][8][9][10][11][12][13][14][15][16][17][18] which is consistent with the bandgap excitation of Ta3N5. The QE was observed >10% for wavelengths ranging between 440 and 520 nm, with a maximum value of 30% at 480 nm.…”

Section: Figure 1 (A) Time Courses Of Photocatalytic Oersupporting

confidence: 92%

“…The free energies of the reactions (6)- (9) allows for estimating the thermodynamics overpotential: (10) This computational approach only calculates the thermodynamic overpotential and hence lacks kinetic information. The potential dependence of the free energy is approximated by the computational hydrogen electrode model which gives good results for coupled proton-electron transfers.…”

Section: Time-resolved Thz Spectroscopymentioning

confidence: 99%

“…[1][2][3][4][5][6] The main challenge lies in identifying materials suitable for efficient photocatalysis, i.e., with an optical response in the visible light region, and energy levels compatible with chemical reduction and/or oxidation. These properties converge in Ta3N5, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] which can theoretically achieve a solar to hydrogen efficiency of approximately 17% using a single semiconductor; nevertheless, non-biased, overall efficient water splitting using this material has not been achieved. For efficient photocatalysis with the powder semiconductor, a solid-electrolyte interface is effectively utilized for charge separation, therein directly inducing surface chemical redox reactions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

et al. 2016

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Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic efficiency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the effects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm 2 V -1 s -1 ), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

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Section: Figure 1 (A) Time Courses Of Photocatalytic Oersupporting

confidence: 92%

Section: Time-resolved Thz Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

et al. 2016

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“…13,17 This illustrates the high potential of the present approach, namely if optimization of the co-catalyst loading is achieved, to improve the performances in the lower applied voltage region.…”

mentioning

confidence: 75%

“…Surface modification with co-catalysts such as IrO 2 , Co 3 O 4 , Co-Pi, and Co(OH) x is reported to stabilize the Ta 3 N 5 photoanode and improve the water splitting efficiency significantly. 13,[17][18][19] To deposit a layer of Co(OH) x nanoparticles on Ta 3 N 5 nanorod arrays as a co-catalyst, the Ta 3 N 5 nanorod array films were simply immersed in a mixed solution of CoSO 4 and NaOH for 25 min, then rinsed with deionized water and finally dried in N 2 . In comparison, the Co-Pi co-catalyst was loaded on the nanorod surface by electrodeposition in a solution of 0.5 mM Co(NO 3 ) 2 in 0.1 M potassium phosphate buffer at pH = 7 at 1 V versus Ag/AgCl for 8 min.…”

mentioning

confidence: 99%

Hydrothermal growth of highly oriented single crystalline Ta₂O₅nanorod arrays and their conversion to Ta₃N₅for efficient solar driven water splitting

Wang

Grigorescu

et al. 2014

Chem. Commun.

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We grow vertically aligned single crystalline Ta 2 O 5 nanorod arrays that can be converted to Ta 3 N 5 nanorod arrays by nitridation.Combined with cobalt phosphate (Co-Pi) as a co-catalyst, such Ta 3 N 5 nanorod photoanodes can yield photocurrent densities of B3.6 mA cm À2 at 1.23 V RHE and B8.2 mA cm À2 at 1.59 V RHE under AM 1.5G (100 mW cm À2 ) irradiation.Hydrogen production via photoelectrochemical (PEC) water splitting has received strongly increased attention in the past few years, as a means to directly convert solar energy into an ideal clean fuel. After the first report by Fujishima and Honda in 1972 1 on hydrogen generation using TiO 2 as a photocatalyst, considerable efforts have been dedicated to tailor the electronic properties and morphology of photocatalysts to improve the efficiency of PEC water splitting. [1][2][3][4] With a band gap of about 2.1 eV and suitable band positions, Ta 3 N 5 can utilize a large portion of the solar spectrum (o600 nm), and is considered to be one of the most promising photoanodes for solar water splitting, as Ta 3 N 5 can reach a theoretical maximum of E16% light conversion under AM 1.5G irradiation. [5][6][7] Various methods such as morphology control, doping and the use of charge transfer catalysts have been introduced to improve the performance of Ta 3 N 5 based PEC cells. [8][9][10] Additionally, structuring of semiconductors at the nanoscale is widely used, not only to provide abundant surface reaction sites but also to aid transport and separation of photoexcited charge carriers. 2 Namely vertically aligned one-dimensional (1D) nanorod arrays are considered to be very promising and efficient structures for energy harvesting systems.A common path to synthesize Ta 3 N 5 is nitridation of Ta 2 O 5 by a high temperature NH 3 treatment. Previous reports on Ta 3 N 5 nanorod fabrication use hydrothermal methods with Ta powders, 11 or a vapor-phase hydrothermal (VPH) process, 12 or use porous anodic alumina (PAA) as a template for through mask anodization with a two-step anodization process, to grow the Ta 2 O 5 precursors. 13 Subsequently these structures are nitrides, and frequently co-catalysts decorated and doped for optimized water splitting performance. A current record efficiency is held by PAA template oxide rods after modification to Ba doped Co-Pi/Ta 3 N 5 nanorods; corresponding photoanodes yielded a photocurrent of 6.3 mA cm À2 at 1.23 V RHE in 0.5 M K 2 HPO 4 solution at a pH of 13. 13 For Ta 3 N 5 nanorods produced by the VPH method and modified with Co(OH) x , a photocurrent density for water splitting of 2.8 mA cm À2 at 1.23 V RHE under AM 1.5G simulated sunlight was obtained. 12a In the present work, we introduce an alternative facile, template free hydrothermal method for the fabrication of vertically aligned Ta 3 N 5 nanorods. For this we grow single crystalline Ta 2 O 5 aligned nanorod arrays on the surface of Ta foils by a direct solution-immersion approach, and then convert these oxide structures to nitrides.To grow the Ta 2 O 5 nanorod array...

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Enhanced Water‐Splitting Performance of Perovskite SrTaO₂N Photoanode Film through Ameliorating Interparticle Charge Transport

Zhong

Zhao

et al. 2016

Adv Funct Materials

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Here SrTaO2N has been found to exhibit photoelectrochemical water splitting, with a theoretical solar‐to‐hydrogen efficiency of 14.4%. Ameliorating the interparticle charge transport by H2 annealing, the solar photocurrent of the SrTaO2N(H) granular film at 1.23 V versus reversible hydrogen electrode (RHE) is increased by ≈250% in comparison with the SrTaO2N film. Using an aberration corrected scanning transmission electron microscope and super‐X energy dispersive spectroscopy, the atomic scale observation has proved a decrease of oxygen concentrations in the surface of SrTaO2N(H) particle, which may allow its electrical conductivity to be increased from 0.77 × 10−6 to 2.65 × 10−6 S cm−1 and therefore the charge separation efficiency has been greatly increased by ≈330%. After being modified by Co–Pi water oxidation catalyst, the SrTaO2N(H) photoanode shows a solar photocurrent of 1.1 mA cm−2 and an incident photo‐to‐current efficiency value of ≈20% at 400–460 nm and 1.23 V versus RHE, which suggests that it is a new promising photoanode material for solar water splitting.

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A Co‐catalyst‐Loaded Ta₃N₅ Photoanode with a High Solar Photocurrent for Water Splitting upon Facile Removal of the Surface Layer

Cited by 215 publications

References 38 publications

Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

Hydrothermal growth of highly oriented single crystalline Ta₂O₅nanorod arrays and their conversion to Ta₃N₅for efficient solar driven water splitting

Enhanced Water‐Splitting Performance of Perovskite SrTaO₂N Photoanode Film through Ameliorating Interparticle Charge Transport

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A Co‐catalyst‐Loaded Ta3N5 Photoanode with a High Solar Photocurrent for Water Splitting upon Facile Removal of the Surface Layer

Cited by 215 publications

References 38 publications

Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

Enhanced Kinetics of Hole Transfer and Electrocatalysis during Photocatalytic Oxygen Evolution by Cocatalyst Tuning

Hydrothermal growth of highly oriented single crystalline Ta2O5nanorod arrays and their conversion to Ta3N5for efficient solar driven water splitting

Enhanced Water‐Splitting Performance of Perovskite SrTaO2N Photoanode Film through Ameliorating Interparticle Charge Transport

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Product

Resources

About

A Co‐catalyst‐Loaded Ta₃N₅ Photoanode with a High Solar Photocurrent for Water Splitting upon Facile Removal of the Surface Layer

Hydrothermal growth of highly oriented single crystalline Ta₂O₅nanorod arrays and their conversion to Ta₃N₅for efficient solar driven water splitting

Enhanced Water‐Splitting Performance of Perovskite SrTaO₂N Photoanode Film through Ameliorating Interparticle Charge Transport