Visible light photocatalytic reduction of water using SrSnO3 sensitized by CuFeO2

Abstract

SrSnO 3-d , prepared in sealed ampoules, crystallizes in the perovskite structure. The band gap is directly allowed at 3.93 eV. The conductivity was found to change markedly and occurs by polaron hopping with activation energy of 0.22 eV. The thermal variation of the thermopower indicates an electron mobility µ e 300K = 3.15×10 -6 cm 2 ×V -1 ×s -1 ), thermally activated. The capacitance measurement shows a linear behavior from which a flat band potential of -0.20 V SCE and an electronic density of 5.56×10 18 cm -3 were determined. The conduction band edge lies below the H 2 O/H 2 level. Accordingly, SrSnO 3-d can be used for water photoreduction when combined with the delafossite CuFeO 2 as sensitizer.The development of optically active semiconductors (SC) is an emerging field of investigation for enabling photovoltaic and photoelectrochemical (PEC) conversions [1]. The stannates ASnO 3 , in which A is an alkaline earth, have gained an increasing interest owing to their technological applications as light-to-electrical and/or chemical energy conversion [2], chemical sensors [3], stable capacitors [4], and more recently water photoelectrolysis [5]. Some strategies to improve the efficiency of PEC devices have been attempted. One of them relies on the splitting between the bands at reduced cations like Sn 2+ or Sb 3+ [6]. These ions have outer ns 2 electrons at energy below the O 2 /H 2 O level in aqueous solutions, and oxygen evolution from water by solar light might be possible. In ASnO 3 , the top of the valence band (VB) is made up of the O 2-2p orbital, whereas the conduction band (CB) is formed mainly by the Sn5s level separated by a forbidden band (E g ) exceeding 3 eV [7]. SrSnO 3 is a white insulator that possesses interesting properties many of which are associated with vacancies, structural defects, or other imperfections. It occurs mostly as n-type material by doping with non-isovalent cations such as rare earth or elements of group V B respectively onto A or Sn sites [8] or through oxygen deficiency by heating under moderate reducing atmosphere [9]. Such processes enhance the spectral response to longer wavelengths and induce a concomitant reduction Sn 4+/2+ . The color turns to gray and one may expect the same origin and mechanism of conductivity. However, whereas little physical characterization of SrSnO 3 has been done [10], to our knowledge no previous investigations concerning the PEC properties have been reported. The presence of tin mixed valences is responsible for enhanced transport properties in deficient stannates, and this paper aims at investigating the electrical properties and PEC characterization of SrSnO 3-d . The main physical parameters, the band energy gap (E g ), the flat band potential (V fb ), and the ionized donor density (N D ), are determined on the basis of absorption spectra and PEC measurements. 1720040-5760/09/4503-0172

Photoelectrochemical characterization of the synthetic crednerite CuMnO2

“…The Cu-Cu length, equal to b-parameter, is longer than that in copper (0.127 nm) 1 and CuMnO 2 is expected to be SC. A large anisotropy is common in the crednerite, and the pellet consists of randomly oriented microcrystal.…”

“…The oxides are among the most stable materials for the water photo electrolysis [1,2]. However, their performances are limited by either a wide forbidden band (E g ) exceeding 3 eV or a large electron affinity, attributed to a low lying valence band (VB) deriving mainly from O 2-: 2p orbital [3].…”

Alkaline earth stannates applied in photocatalysis: prospection and review of literature

“…The other five papers displayed in Table IV use SrSnO 3 as a photocatalyst. Although doping was not used for this material, different co-catalysts were evaluated [15,44,46,50,52]. The morphology and the use of nanoparticles were also evaluated in [15,44,52] to improve the surface area and the photocatalytic efficiency.…”

Investigation of the tunnel magnetoresistance in junctions with a strontium stannate barrier

“…10). Up to now SSO has only been used as a transparent conductive layer, when doped with La, Ba, [11][12][13] as an insulation barrier with a high dielectric constant in single flux quantum circuits 14 , and as a photoelectrochemical converter for the reduction of water 15 . a) Electronic mail: Matthias.Althammer@wmi.badw.…”