Study of the O<i>K</i>-edge XANES of Cobalt-doped ZnO diluted magnetic semiconductors

Shi, Tongfei; Wang, Yuqi; Yin, Zhijun; Zhang, Yunpeng; Shen, Yan

doi:10.1088/1742-6596/193/1/012099

Cited by 1 publication

(1 citation statement)

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“…8a): the peaks for the transition around 7726 eV are not fully separated for Co-foil compared to Co-Pc-1000, indicating that the Co structures are still somewhat different. This discrepancy does not occur in the study by Martins Alves et al [8], where the Co 0 spectrum was different from that reported by us and in the literature [63][64][65] and the peaks are not separated; such an effect could be attributed to different sizes of the metal clusters, as shown in a recent study [65].…”

Section: Xafscontrasting

confidence: 78%

Pyrolyzed phthalocyanines as surrogate carbon catalysts: Initial insights into oxygen-transfer mechanisms

Vallejos-Burgos

Utsumi

Hattori

et al. 2012

Fuel

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a b s t r a c tDeposited and heat-treated phthalocyanines are promising electrocatalysts for replacing platinum in the oxygen reduction reaction (ORR), the most important process in energy conversion systems such as fuel cells; and yet its key mechanistic features are not well understood. To optimize their use, it is necessary to understand their behavior in the absence of an electric field. In the pursuit of this goal, we pyrolyzed metal-free, cobalt and copper phthalocyanines between 550 and 1000°C and studied their structural and chemical changes by elemental analysis, N 2 and CO 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray analysis fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was assessed by non-isothermal O 2 gasification and NO reduction reactions. A comparison of these results with their other properties allowed us to reach the following conclusions: (i) the loss of reactivity of metal-free phthalocyanine with heat treatment is attributed to its structural annealing and heteroatom loss, with the porosity changes having no effect; (ii) for metal phthalocyanines at intermediate heat treatment temperatures, the optimum in reactivity correlates with the micropore surface area and the presence of metal particles, with no influence of nitrogen content; (iii) the coordination metal increases phthalocyanine thermal stability in an inert atmosphere, but in an oxidizing atmosphere it acts as a gasification catalyst even below decomposition temperatures. The implications of these findings for catalytic oxygen-transfer mechanisms are discussed.

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