Water reduction and oxidation on Pt–Ru/Y₂Ta₂O₅N₂catalyst under visible light irradiation

Abstract

Y 2 Ta 2 O 5 N 2 is presented as a novel photocatalyst with high activity for water splitting under visible-light irradiation in the presence of appropriate sacrificial reagents; the activity for reduction to H 2 is increased by the incorporation of Pt or Ru as a co-catalyst, with a significant increase in production efficiency when both Pt and Ru are present.Photocatalytic splitting of water using solar energy is a challenging and interesting topic of research with the potential to provide clean and renewable H 2 as an energy resource. To date, many mixedmetal oxides such as K 2 La 2 Ti 3 O 10 , 1 NaTaO 3 , 2 and LnTaO 4 (Ln = La, Pr, Ce, Nd, Sm) 3 have been studied for water splitting as a means of producing both H 2 and O 2 , as such oxides have excellent stability and high activity. However, these catalysts are only active under ultraviolet (UV) light, which accounts for only a small fraction (5%) of the solar spectrum at the earth's surface. Therefore, the development of visible-light responsive photocatalysts for overall water splitting is currently attracting much attention as a potentially efficient utilization of solar energy. [4][5][6] Considerable effort has been made to extend the absorption edge of semiconductors with wide bandgaps into the visible-light region. 7,8 The incorporation of non-metal atoms (C, N, F, P and S) into metal-oxide lattices is one way to narrow the bandgap of the parent oxide because of their p states mixing with O 2p states. 9-11 A number of non-oxide photocatalysts have recently been reported to be promising candidates for overall water splitting under visiblelight irradiation. 6,12,13 Oxynitrides such as TaON and LaTiO 2 N have been shown to exhibit absorption in the visible region and stable photocatalytic activity for water reduction and oxidation using appropriate sacrificial reagents. However, the range of oxynitride photocatalysts synthesized to date remains limited. Although platinum is already generally considered to be the best metal promoter for H 2 production from water due to its low overpotential, it has been recently shown to exhibit remarkably enhanced efficiency for H 2 evolution under visible light when Ru was deposited on TaON. 14 This increased efficiency has been attributed to improved contact between the TaON and Ru. However, the simultaneous use of Pt and Ru as promoters of photocatalytic water reduction has yet to be reported.This communication reports Y 2 Ta 2 O 5 N 2 as a novel visible lightdriven photocatalyst with high activity for oxidation of water in the presence of a sacrificial electron acceptor (Ag 1 ). This catalyst also reduces water to H 2 in the presence of a sacrificial electron donor (ethanol) and Pt or Ru as a co-catalyst, with a significant enhancement of H 2 production efficiency in the presence of both Pt and Ru. The photocatalytic reaction was carried out in a closed gas circulation and evacuation system under a 300 W Xe lamp equipped with a cut-off filter (l w 420 nm). Photocatalytic water reduction and oxidation were performed us...

Highly efficient photocatalytic oxidation of sulfur-containing organic compounds and dyes on TiO2 with dual cocatalysts Pt and RuO2

“…Compared with TiO 2 loaded with individual cocatalyst, the activity was also improved when Pt and other MO x (M = Ir, Co, V, Mn, Ni and Fe) were co-loaded on TiO 2 , or other noble metals (e.g., Pd, Au, Ni and Cu) and RuO 2 were co-loaded on TiO 2 . Above results show that Pt-RuO 2 /TiO 2 is the most effective photocatalyst for the 4 could result in an enhancement of photocatalytic activity in the photocatalytic water splitting [17,18] and photocatalytic oxidation of thiophene [19]. Fig.…”

“…The interaction of the active oxygen species ( • OH, O 2 •− and O 2 2− ) with the pollutant captured the photo-generated hole initiate a series of oxidation reactions. The synergistic effect of RuO 2 acting as an oxidation cocatalyst and Pt acting as a reduction cocatalyst is beneficial for the efficient separation and transfer of the photo-excited electrons and holes [17][18][19], being responsible for the high photocatalytic oxidation activity for the degradation of pollutants.…”

“…It is reported that loading a small amount of noble metals or metal oxides, such as Pt, Ag, NiO, and RuO 2 on TiO 2 [12,13], greatly improves the activity of the photocatalysts [14,15]. However, few researches have been reported for dual cocatalysts effect on the photocatalytic activity of a TiO 2 based photocatalyst for photocatalytic waste oxidation [16][17][18]. Moreover, the synergistic effect of dual cocatalysts is far less investigated in the photocatalysis for environmental protection.…”

New layered semiconductors for efficient photoelectrochemical hydrogen and oxygen generation

“…[1][2][3][4] Since the first report of employing TiO 2 electrode for photoelectrochemical water splitting in 1972, 5 great efforts have been devoted to the research on solar energy conversion, especially on the development of novel photocatalysts with high efficiency, stability, and availability for water splitting to produce H 2 as an energy carrier. [6][7][8][9][10][11][12] Up to now, more than 100 photocatalysts including oxides, sulphides, phosphide, (oxy)nitrides, and (oxy)sulfides have been developed. However, the efficiency of all the semiconductors is too low to be applicable in practical applications, and it is highly desirable to develop strategies that could further modify semiconductors towards efficient photocatalysis.…”

Synthesis and characterization of aurivillius phase Bi5Ti3FeO15 layered perovskite for visible light photocatalysis

“…Despite many efforts, 1)-4) the design of the materials showing a high activity under visible light is still a major challenge in the field. One promising approach to develop new photocatalysts is the tuning of the optical properties of UV light active catalysts by substitutional doping, as demonstrated in LaTiO2N, 5) TaON, 6) Y2Ta2O5N2, 7) Sr2Nb2O7-xNx, 8) TiO2-xCx, 9)-11) or TiO2-xNx 12) for anionic doping, and in metal ion-implanted TiO2, 13) TiO2 or SrTiO3:Sb/ Cr/ M (Ru, Rh, Ir, Pt, Pd), 14), 15) BaSnO3:Pb 16), 17) and La2Ti2O7:Cr/ Fe, 18) for cationic doping. However, this kind of substitutional doping, in most of the cases, resulted in a small absorption in the visible light region with the original band gap absorption intact, rather than a total red-shift of the band gap energy.…”