Surface Modification of TaON with Monoclinic ZrO2 to Produce a Composite Photocatalyst with Enhanced Hydrogen Evolution Activity under Visible Light

Maeda, Kazuhiko; Terashima, Hiroaki; Kase, Kentaro; Higashi, Masanobu; Tabata, Masaji; Domen, Kazunari

doi:10.1246/bcsj.81.927

Cited by 146 publications

(134 citation statements)

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“…The as-prepared material was confirmed by XRD, SEM, and TEM to be a composite of monoclinic ZrO 2 and TaON, and the loaded ZrO 2 species existed on the TaON component in the form of nanoparticles (1030 nm in size). 102,103 With increasing ZrO 2 content, the ZrO 2 modifiers tended to aggregate. Figure 15A shows UVvisible diffuse reflectance spectra of TaON and ZrO 2 /TaON.…”

Section: Preparation and Characterizationmentioning

confidence: 99%

“…102 Specifically, monoclinic ZrO 2 nanoparticles are dispersed on the surface of a Ta 2 O 5 precursor before nitridation, thereby protecting Ta 5+ cations in the TaON surface from being reduced by H 2 (derived from disassociation of NH 3 at high temperatures) during nitridation. The reduction of Ta 5+ cations in TaON during nitridation generates reduced tantalum species, resulting in the production of anionic vacancies to maintain the charge balance of the material.…”

Section: Application To Cr 2 O 3 Modification To Metal Oxidementioning

confidence: 99%

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Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

Maeda

Domen

2016

Bulletin of the Chemical Society of Japan

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155

110

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Overall water splitting using a semiconductor photocatalyst with sunlight has long been viewed as a potential means of large-scale H 2 production from renewable resources. In general, the reaction can be accomplished when a photocatalyst is modified with a suitable cocatalyst that efficiently promotes water reduction. It is therefore essential to develop both photocatalysts and cocatalysts in harmony. Certain metal (oxy)-nitrides are potential candidates as water-splitting photocatalysts because of their suitable band edge positions for water reduction/oxidation, small band gaps (<3 eV), and stability under irradiation. However, efficient water splitting using visible-light-responsive oxynitrides has still remained a challenge. This account describes our recent developments over the last 10 years of new oxynitrides as well as cocatalysts for overall water splitting under visible light.

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Section: Preparation and Characterizationmentioning

confidence: 99%

Section: Application To Cr 2 O 3 Modification To Metal Oxidementioning

confidence: 99%

Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

Maeda

Domen

2016

Bulletin of the Chemical Society of Japan

Self Cite

155

110

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“…Modifying Ta 2 O 5 with ZrO 2 prior to nitridation effectively suppressed the reduction of pentavalent Ta ions during nitridation [57]. Figure 8 shows the absorption spectra of TaON and ZrO 2 -modified TaON [57].…”

Section: Taon-based Photocatalystmentioning

confidence: 99%

“…Figure 8 shows the absorption spectra of TaON and ZrO 2 -modified TaON [57]. Unmodified TaON exhibits light absorption due to reduced Ta species at a wavelength longer than 500 nm, the absorption edge wavelength of TaON.…”

Section: Taon-based Photocatalystmentioning

confidence: 99%

Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

2014

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Some particulate semiconductors loaded with nanoparticulate catalysts exhibit photocatalytic activity for the water-splitting reaction. The photocatalysis is distinct from the thermal catalysis because photocatalysis involves photophysical processes in particulate semiconductors. This review article presents a brief introduction to photocatalysis, followed by kinetic aspects of the photocatalytic water-splitting reaction.

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“…10,11 Another way is to change the path of water oxidation to lower the kinetic barrier and reduce the overpotential required for water oxidation.…”

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confidence: 99%

Enhanced photocatalytic water oxidation on ZnO photoanodes in a borate buffer electrolyte

Xiong¹,

Shi²,

Wang³

et al. 2013

Catal. Sci. Technol.

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Solar fuels can be produced from photocatalytic, photoelectrochemical or photovoltaic-electrochemical splitting of H 2 O and conversion of CO 2 . In these processes, the water oxidation reaction is involved. The water oxidation reaction is complicated with transfer of 4 electrons and 4 protons. Calculation results showed that the free energy change of the rate-controlling step of water oxidation is as high as B0.6 eV at the overpotential of 0.7 V on the TiO 2 surface, 1 and transient absorption spectroscopy revealed that the water oxidation is as slow as on the scale of sub-seconds. 2 On the other hand, the valence bands of semiconductors like TiO 2 are still sufficiently positive to meet the energy requirement. As an analogue of TiO 2 , ZnO is similar in band gap and positions of CB and VB. 3 ZnO is has been studied as a photoanode for water oxidation as well, 4-6 but gives insufficient efficiency. There are some other reasons for low efficiency of water oxidation on photoanodes. Most photo-generated holes are trapped by defect sites or surface species except for intrinsic recombination. 2,7,8 The trapping reduces the energy of holes and thus the oxidizing ability. Furthermore the trapped sites and surface species may act as recombination centers which results in a much shorter lifetime of the holes. Most holes are recombined before driving water oxidation reaction, so the quantum efficiency (QE) is very low. Applying high potential on the photoanode inhibits recombination by extracting electrons, but it requires external bias and thus consumes external energy. 9In order to increase the QE, one way is to remove the recombination centers by improving the crystallinity of the semiconductor and by surface modification. 10,11 Another way is to change the path of water oxidation to lower the kinetic barrier and reduce the overpotential required for water oxidation.Cocatalysts are deposited on the semiconductor photoanode to reduce the overpotential of water oxidation reaction, such as IrO 2 , 12,13 Co 3 O 4 , 13-15 FeOOH, 16 and a Co-based catalyst deposited with phosphate buffer (known as Co-Pi). 6,[17][18][19] In the studies using Co-Pi as a cocatalyst, usually phosphate buffer solution is also employed as an electrolyte, following the original research on electrocatalytic water oxidation using Co-based catalysts deposited with various buffers including phosphate, methylphosphate and borate. 20,21 A few studies showed that the activity of the assisted photoanodes in a buffered phosphate electrolyte is higher than that in an unbuffered sulfate electrolyte with the same pH. 22In this work, we found that even without adding a source of valence-variable metals, such as Fe, Co or Ni, water oxidation on ZnO photoanodes was enhanced by in situ photoelectrochemical reaction in B BS or treatment at 75 1C in concentrated B BS . ZnO photoanodes used in this study were fabricated on FTO with a seed layer by galvanostatic cathodic deposition from a solution of 5 mM Zn(NO 3 ) 2 and 50 mM KNO 3 at 70 1C. A base forms from the re...

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Surface Modification of TaON with Monoclinic ZrO2 to Produce a Composite Photocatalyst with Enhanced Hydrogen Evolution Activity under Visible Light

Cited by 146 publications

References 50 publications

Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

Enhanced photocatalytic water oxidation on ZnO photoanodes in a borate buffer electrolyte

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