Pt/SrTiO

Figure 35. Impedance spectra of the cell O2, Pt SrTiOs SrTiOs Pt, O2 as function of d.c. bias. Electrodes are parallel to the bicrystal boundary (Z5 tilt grain boundary, iron content 2 x 10 cm ). Both bulk and boundary resistances are predominantly electronic resistances.Reprinted from I. Denk, J. Claus and J. Maier, J. Electrochem. Soc., 144 (1997) 3526-3536. Copyright 1997 with permission from The Electrochemical Society.

In this type of cell both electrodes are immersed in the same constant pH solution. An illustrative cell is [27,28] n-SrTiOs photoanode 9.5-10 M NaOH electrolyte Pt cathode. The underlying principle of this cell is production of an internal electric field at the semiconductor-electrolyte interface sufficient to efficiently separate the photogenerated electron-hole pairs. Subsequently holes and electrons are readily available for water oxidation and reduction, respectively, at the anode and cathode. The anode and cathode are commonly physically separated [31-34], but can be combined into a monolithic structure called a photochemical diode [35]. 

Wagner FT, Somerjai GA (1980) Photocatalytic production from water on Pt-free SrTiOs in aqueous alkaline solution. Nature 285 559-560... 

Figure 8. Simultaneous measurements of Hs yield and integrated current passed as a function of NaOH electrolyte concentration for a n-SrTiOs/Pt PEC cell ((left) gas chromatography ("right,) coulometry). Each vertical division corresponds to the equivalent of 5000 monolayers Ht produced. ((A) 0.01 F (O) 1 F (SJ) 10 F ...

It is possible that the third site is gaseous hydrogen, not explicitly considered in the analysis. As shown in Fig. 28a, the shift vs intensity curve for the H/Rh signal of this sample is Hat up to approximately one monolayer (50), and could possibly be represented by the Nottingham model for H/Pt (described in Section III.D). This is not the case, however, for a very similar Rh/SrTiOs catalyst (51) (Fig. 28b). 

In Ref. [379], the isotopic carbon ( " C) atom distribution in the Ir (150-nm thick) layer, deposited on a SrTiOa substrate after a BEN step using C-methane, was investigated by elastic recoil detection (ERD) of a 170-MeV iodine atomic beam. The C atoms existed both at the substrate surface and near the Ir/SrTiOs interface. The fact that carbon diffuses into Ir to reach SrTiO is similar to that of Pt described in Section 12.1, although the diffusion rate was smaller for Ir. 

There are a whole range of lead-containing relaxors based on lead zinc niobate (PZN), lead iron niobate (PFN), lead iron tungstate (PFW), and solid solutions with each other and with BaTiOs (BT), PbTi03 (PT), and SrTiOs (ST). Some of the solid-solution phases are PMN-PT, PMN-PT-PZN, PMN-PZN, PFN-PFW, PFN-PMN, and PFW-PT. 

Domen and co-workers first succeeded in the photocatalytic decomposition of pure water into H2 and O2 NiO-loaded SrTiOs powder [242,243]. The NiO cocatalyst for H2 evolution is usually activated by H2 reduction and subsequent O2 oxidation to form a NiO/Ni doublelayer structure that is convenient for electron migration from a photocatalyst substrate to a cocatalyst [332]. The pretreated NiO cocatalysts often denoted as NiO in the literature. The NiO cocatalyst does not cause the back reaction between H2 and O2, being different from Pt. The excellent NiO cocatalyst has often been employed for many photocatalysts for water splitting. Rh is also a suitable cocatalyst for the SrTiOa photocatalyst [333]. 

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