EC-XPS

Here, we demonstrate clear and direct evidence for the modified electronic structures of surface Pt atoms in Pt-Co and Pt-Ru by using EC-XPS [Wakisaka et al., 2006]. The sample electrode was transferred between an XPS chamber and an electrochemical (EC) chamber without exposure to air (to minimize contamination of the surface). All photoelectron spectra, including the valence level region) were taken by using a monochromatic Al Ka (hv = 1486.58 eV). The uncertainty of binding energy measurement was less than + 0.03 eV. 

Wakisaka M, Mitsui S, Hirose H, Kawashima K, Uchida H, Watanabe M. 2006. Electronic structures of Pt-Co and Pt-Ru alloys for CO-tolerant anode catalysts in polymer electrol3de fuel cells studied by EC-XPS. J Phys Chem B 110 23489-23496. 

The solution space of the kinetic model includes the electrical current as a function of the transient potential, normalized to the scan rate, in addition to coverages of different surface oxide species considered. Using parameters obtained from the fits of CV scans, steady-state coverages as a function of potential in the limit of 0 can be evaluated. Figure 3.19 compares these coverages with coverage values obtained by analysis of EC-XPS data (Wakisaka et al., 2010). Among parameters obtained... 

FIGURE 3.19 Species coverage in the oxide formation and reduction model in the limit of zero scan rate (potentiostatic) compared with EC-XPS data from Wakisaka et al. (2010). (Reprinted from Electrocatalysis, Mechanistic principles of platinum oxide formation and reduction, 2014, 1-11, Rinaldo et al. Copyright (2014) Springer. With permission.)... 

Lithium carbonate and hydrocarbon were identified in XPS spectra of graphite electrodes after the first cycle in LiPF6/EC-DMC electrolyte [104]. Electrochemical QCMB experiments in LiAsF6/EC-DEC solution [99] clearly indicated the formation of a surface film at about 1.5 V vs. (Li/Li+). However the values of mass accumulation per mole of electrons transferred (m.p.e), calculated for the surface species, were smaller than those of the expected surface compounds (mainly (CF OCC Li ). This was attributed to the low stability of the SEI and its partial dissolution. 

Table 4. XPS measurements of HOPG after one cycle in 1.2 mol L 1 LiAsF6 /EC-DEC electrolyte...

Liu Y, Tang XP, McArthur JC, Scott J, Gartner S (2000) Analysis of human immunodeficiency virus type 1 gpl60 sequences from a patient with HIV dementia evidence for monocyte trafficking into brain. J Neurovirol 6(Suppl 1) S70-S81 Liu H, Dow EC, Arora R, Kimata JT, Bull LM, Arduino RC, Rice AP (2006) Integration of human immunodeficiency virus type 1 in untreated infection occurs preferentially within genes. J Virol 80(15) 7765-7768... 

Varazo K, Lay MD, Sorenson TA, Stickney JL (2002) Formation of the first monolayers of CdTe on Au(l 11) by electrochemical atomic layer epitaxy (EC-ALE) studied by LEED, Auger, XPS, and in-situ STM. J Electroanal Chem 522 104-114... 

The change in the electronic properties of Ru particles upon modification with Se was investigated recently by electrochemical nuclear magnetic resonance (EC-NMR) and XPS [28]. In this work, it was established for the first time that Se, which is a p-type semiconductor in elemental form, becomes metallic when interacting with Ru, due to charge transfer from Ru to Se. On the basis of this and previous results, the authors emphasized that the combination of two or more elements to induce electronic alterations on a major catalytic component, as exemplified by Se addition on Ru, is quite a promising method to design stable and potent fuel cell electrocatalysts. 

Babu PK, Lewera A, Chung JH, Hunger R, Jaegermann W, Alonso-Vante N, Wieckowski A, Oldfield E (2007) Selenium becomes metallic in Ru-Se fuel cell catalysts An EC-NMR and XPS investigation. J Am Chem Soc 129 15140-15141... 

We have found new CO-tolerant catalysts by alloying Pt with a second, nonprecious, metal (Pt-Fe, Pt-Co, Pt-Ni, etc.) [Fujino, 1996 Watanabe et al., 1999 Igarashi et al., 2001]. In this section, we demonstrate the properties of these new alloy catalysts together with Pt-Ru alloy, based on voltammetric measurements, electrochemical quartz crystal microbalance (EQCM), electrochemical scanning tunneling microscopy (EC-STM), in situ Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). 

Each test electrode was transferred to the EC chamber and subjected to electrochemical stabilization. The EC chamber was then evacuated rapidly by two sorption pumps and a cryopump to transfer the electrode to the XPS chamber again. 

In addition to ET-IR, XPS experiments performed on a graphite anode that had been cycled in various carbonate-based electrolytes also identified an alkyl carbonate species. Bar-Tow et al. characterized the surface of a highly oriented pyrolytic graphite (HOPG) that had been cycled in LiAsEe/EC/DEC and found the C Is signal located at 289 eV, which had been... 

Figure 22. C Is, O Is, F Is, P 2p, Li Is, and Ni 2p XPS spectra for LiNio.8Coo.2O2 cycled in LiPFe/EC/DEC. (Reproduced with permission from refs 294 (Figure 6). Copyright 2002 The Electrochemical Society.)...

More recent XPS studies were conducted by Ander-sson et al. on a similar LiNio.8Coo.2O2 cathode cycled in LiPFe/EC/DEC. and more detailed efforts were made to assign the signature signals for various... 

Figure 40. XPS C Is and FIs spectra of graphitic anodes cycled in 1.0 M LiAsFe/EC/DMC electrolyte. 5% VC was used as additive in the left spectra. Note the different scales for the two FIs spectra. (Reproduced with permission from ref 404 (Figure 10). Copyright 2002 Elsevier.)...

---