Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

Hisatomi, Takashi; Takanabe, Kazuhiro; Domen, Kazunari

doi:10.1007/s10562-014-1397-z

Cited by 238 publications

(181 citation statements)

References 65 publications

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“…This behavior has generally been observed in the powder system due to the competitive light absorption by the semiconductor photocatalysts and the cocatalysts, and the requirement of both reduction and oxidation sites. 14, [44][45][46][47] Ta 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 13 non-treated Ta 3 N 5 , suggesting that the improvement of photocatalytic activity was not due to the hydrothermal treatment of Ta 3 N 5 , but to the presence of NiFeO x catalyst decorated onto Ta 3 N 5 .…”

Section: Photocatalytic Investigation Of Nifeo Xmentioning

confidence: 99%

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

et al. 2016

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The present work compares the oxygen evolution reaction (OER) in electrocatalysis and photocatalysis in aqueous solutions using nanostructured NiFeO x as catalysts. The impacts of pH and reaction temperature on the electrocatalytic and photocatalytic OER kinetics were investigated. For electrocatalysis, a NiFeO x catalyst was hydrothermally decorated on Ni foam. In 1 M KOH solution, the NiFeO x electrocatalyst achieved 10 mA cm −2 at an overpotential of 260 mV. The same catalyst was decorated on the surface of Ta 3 N 5 photocatalyst powder. The reaction was conducted in the presence of 0.1 M Na 2 S 2 O 8 as a strong electron scavenger, thus likely leading to the OER being kinetically relevant. When compared with the bare Ta 3 N 5 , NiFeO x /Ta 3 N 5 demonstrated a 5-fold improvement in photocatalytic activity in the OER under visible light irradiation, achieving a quantum efficiency of 24% at 480 nm. Under the conditions investigated, a strong correlation between the electrocatalytic and photocatalytic performances was identified: an improvement in electrocatalysis corresponded with an improvement in photocatalysis without altering the identity of the materials. The rate change at different pH was likely associated with electrocatalytic kinetics that accordingly influenced the photocatalytic rates. The sensitivity of the reaction rates with respect to the reaction temperature resulted in an apparent activation energy of 25 kJ mol −1 in electrocatalysis, whereas the apparent activation energy in photocatalysis was 16 kJ mol −1 . The origin of the difference in these activation energy values is likely attributed to the possible effects of temperature on the individual thermodynamic and kinetic parameters of the reaction process. The work described herein demonstrates a method of "transferring the knowledge of electrocatalysis to photocatalysis" as a strong tool to rationally and quantitatively understand the complex reaction schemes involved in photocatalytic reactions.

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Section: Photocatalytic Investigation Of Nifeo Xmentioning

confidence: 99%

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

et al. 2016

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“…This is a general trend for powder systems due to the requirement for sites for both reduction and oxidation and potential competitive light absorption from Co species. 25,[48][49][50] To further elucidate the state of the catalyst after pretreatment, 2 wt% CoO x /Ta 3 N 5 treated at 700 °C under NH 3 was selected for further study unless otherwise noted. The XRD patterns of Ta 3 N 5 and CoO x /Ta 3 N 5 are compared in Figure 2.…”

Section: Photocatalytic Reactionmentioning

confidence: 99%

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

et al. 2015

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ABSTRACT:In a photocatalytic suspension system with a powder semiconductor, the interface between the photocatalyst semiconductor and catalyst should be constructed to minimize resistance for charge transfer of excited carriers. This study demonstrates an in-depth understanding of pretreatment effects on the photocatalytic O 2 evolution reaction (OER) activity of visible-lightresponsive Ta 3 N 5 decorated with CoO x nanoparticles. The CoO x /Ta 3 N 5 sample was synthesized by impregnation followed by sequential heat treatments under NH 3 flow and air flow at various temperatures. Various characterization techniques, including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS), were used to clarify the state and role of cobalt. No improvement in photocatalytic activity for OER over the bare Ta 3 N 5 was observed for the as-impregnated CoO x /Ta 3 N 5 , likely because of insufficient contact between CoO x and Ta 3 N 5 . When the sample was treated in NH 3 at high temperature, a substantial improvement in the photocatalytic activity was observed. After NH 3 treatment at 700 °C, the Co 0 -CoO x core-shell agglomerated cobalt structure was identified by XAS and STEM. No metallic cobalt species was evident after the photocatalytic OER, indicating that the metallic cobalt itself is not essential for the reaction. Accordingly, mild oxidation (200 °C) of the NH 3 -treated CoO x /Ta 3 N 5 sample enhanced photocatalytic OER activity. Oxidation at higher temperatures drastically eliminated the photocatalytic activity, most likely because of unfavorable Ta 3 N 5 oxidation. These results suggest that the intimate contact between cobalt species and Ta 3 N 5 facilitated at high temperature is beneficial to enhancing hole transport and that the cobalt oxide provides electrocatalytic sites for OER. IntroductionWater splitting using powder photocatalyst systems has attracted significant interest for the production of renewable hydrogen generation using abundant solar energy because of its simplicity, scalability, and low capital cost.1,2 To effectively convert solar energy, substantial utilization of photon energy in the visible-light range is essential. Using the AM 1.5G standard spectrum 3 , a photocatalyst with absorption from UV to 600 nm with a quantum efficiency of 30% accounts for ~5% solar to hydrogen efficiency, making the technology commercially feasible.1,4 Among the photocatalysts investigated to date, tantalum(V) nitride (Ta 3 N 5 ) has emerged as one of the most promising candidates and has been extensively investigated for more than a decade. [4][5][6][7][8][9][10][11][12][13][14][15] Ta 3 N 5 has a visible-light response (approximately 600 nm, ~2.1-eV band gap) and is capable of producing hydrogen or oxygen in the presence of appropriate sacrificial reagents and surface modifications under visible-light irradiation. 1,[5][6][7][8][9][10][11][12][13][14][15][16] Our recent work on Ta 3 N 5 thin films for the photo...

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“…46 For the purpose of this review, 25 1C was used as the standard temperature, because that is approximately the temperature utilized for the laboratoryscale demonstrations reported below.…”

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confidence: 99%

Particle suspension reactors and materials for solar-driven water splitting

Fabian

Singh

et al. 2015

Energy Environ. Sci.

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Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

Cited by 238 publications

References 65 publications

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

Particle suspension reactors and materials for solar-driven water splitting

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Photocatalytic Water-Splitting Reaction from Catalytic and Kinetic Perspectives

Cited by 238 publications

References 65 publications

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

Temperature Dependence of Electrocatalytic and Photocatalytic Oxygen Evolution Reaction Rates Using NiFe Oxide

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta3N5 Photocatalyst

Particle suspension reactors and materials for solar-driven water splitting

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Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst