Electrochemical XANES

Mn02) [56], The XANES spectra at the Ni K-edge indicates that, unlike the ABS alloys, there is very little interaction between hydrogen and Ni but rather strong interactions with Ti, V, and Zr. The hydrogen is presumably located in tetrahedra that contain large fractions of these three elements, whereas the Ni-rich sites are probably empty. Thus the function of Ni in AB2 alloys may be primarily to serve as a catalyst for the electrochemical hydriding reactions. 

Figure 13. Pt L3 XANES of 4 wt % Pt/C electrodes (left, 3.7 nm diameter particles right, <1.0 nm diameter particles) at (a) -0.2 V, (b) 0.5 V, and (c) 1.0 V vs SSCE.39 (Reproduced with permission from ref 39. Copyright 1994 The Electrochemical Society, Inc.)...

The lithiated transition metal oxide LiVMoOe has been synthesized by solid state reaction. This is the first report of this compound to be studied as an anode material. The synthesized LiVMo06 powder has been studied by means of X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) spectroscopy. The electrochemical characteristics of the prepared electrodes assembled in coin cells were also investigated in terms of half-cell performance. It is observed that the cell exhibits three stages of discharge plateaus in the ranges 2.1-2.0 V, 0.6-0.5 V and 0.2-0.01 V, respectively. 

Figure 9. In situ Pt L3 XANES data taken in a PAFC and PEMFC. The PEMFC (grey) are taken at 0.66 V (dotted) and 0.72 V (solid) vs. RHE. The PAFC fuel cell data (black) were taken at 0.6 (dotted), 0.75 (long dotted) and 0.85 V (dot-dashed) vs. RHE. Electrochemical cell data at 0.74 V vs RHE in H2SO4 is also shown (thin, continuous line). The regions for OH, OOH and anion adsorption are indicated.

Our research focuses on mechanistic and kinetic studies of photochemical and electrochemical CO2 reduction that involves metal complexes as catalysts. This work makes use of UV-vis, NMR, and FTIR spectroscopy, flash photolysis, pulse radiolysis. X-ray diffraction, XANES (X-ray absorption near-edge spectroscopy) and EXAFS (extended X-ray absorption fine structure). Here we summarize our research on photochemical carbon dioxide reduction with metal macrocycles. 

P L2,3 XANES of porous InP grown on monocrystalline InP <100> by pulse anodic electrochemical etching of substrates in electrolytes containing HF, HCl or HBr are presented in Fig. 2 (left). USXES spectra of por-InP etched in HCl ambient is presented in Fig. 2 (right) together with those for monocrystalline InP. 

Due to its rich electronic and electrochemical behavior, and to its versatile chemical reactivity, fullerene Cgo has been considered as the ideal partner in photo-induced processes [28, 111, 112]. Cgo>in fact, is a good electron-acceptor, and has a low reorganization energy [113]. For these reasons, an increasingly high number of donors have been covalently linked to Cgo > for potential use as novel electronic materials and for applications in artificial photosynthesis. Many classes of donor units have been attached to Cgo > including aromatics [ 12, 13, 114-118], porphyrins [11, 119-125] and phthalocyanins [126, 127], rota-xanes [128,129],tetrathiafulvalenes [130-133],carotenes [125],Ru-bipy- [134, 135] and Ru-terpy- [135,136] complexes, as well as ferrocene [130,137]. 

Fig. 5.100. Electrochemical cell for XANES/SEXAFS measurements in the transmission mode (based on a design in [576])...

A.J. Davenport, M. Sansone, High resolution in-situ XANES investigation of the nature of the passive film on iron in a pH 8.4 borate buffer, J. Electrochem. Soc. 142 (1995) 725—730. 

Schmucki, P, Virtanen, S, Isaacs, HS, Ryan, MP, Davenport, AJ, Bohni, H, Stenberg, T. 1998. Electrochemical Behavior of Cr203/Fe203 Artificial Passive Films Studied by in situ XANES. J. Electrochem. Soc., 145, 791. 

In order to get answers to these questions, the ability to better characterize catalysts and electrocatalysts in situ under actual reactor or cell operating conditions (i.e., operando conditions) with element specificity and surface sensitivity is crucial. However, there are very few techniques that lend themselves to the rigorous requirements in electrochemical and in particular fuel cell studies (Fig. 1). With respect to structure, in-situ X-ray diffraction (XRD) could be the method of choice, but it has severe limitations for very small particles. Fourier transform infra red (FTTR), " and optical sum frequency generation (SFG) directly reveal the adsorption sites of such probe molecules as CO," but cannot provide much information on the adsorption of 0 and OH. To follow both structure and adsorbates at once (i.e., with extended X-ray absorption fine stmcture (EXAFS) and X-ray absorption near edge stmc-ture (XANES), respectively), only X-ray absorption spectroscopy (XAS) has proven to be an appropriate technique. This statement is supported by the comparatively large number of in situ XAS studies that have been published during the last decade. 16,17,18,19,20,21,22,23,24,25 highly Versatile, since in situ measme-... 

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