Structure of Bimetallic Particles:  Nonequimolar Graphite-Supported Fe−Pd

Abstract

This investigation established the effects of bulk immiscibility on the bulk and surface structure of FePd catalyst particles supported on graphite. By use of Mössbauer effect spectroscopy, X-ray diffraction and gas-adsorption microcalorimetry, it was shown that iron-rich FePd/Grafoil catalyst particles consist of thermodynamically stable segregated states of metallic iron and FePd alloy in accordance with the bulk immiscibility of the two phases. This indicates that manipulation of metal stoichiometry in bimetallic catalyst particles with weak metal support interaction provides another means to modify particle structure and hence catalytic chemistry.

Bimetallic Pd96Fe4 nanodendrites embedded in graphitic carbon nanosheets as highly efficient anode electrocatalysts

“…The (111) peak position in Fe-Pd appears at a slightly higher scattering angle compared to that of Pd nanoparticles, indicating the formation of a Pd-Fe alloy. 80,81 XPS analysis of the as-synthesized Pd-Fe/GCN was conducted to elucidate the composition and oxidation state of metal present in the nanohybrids as shown in Fig. 5.…”

OPTIMIZATION OF CHAR FOR NOx REMOVAL

“…Instrument. Microcalorimetry techniques have an excellent potential for providing unprecedented insight into the structure and surface chemistry of high surface area materials, such as acid catalysts [53], supported metal catalysts [54], as well as carbons [55][56][57]. They can provide precise information concerning the concentration and nature of the active sites existing on carbon surfaces.…”

“…The microcalorimeter used in this work was designed , built and developed under the direction of Dr. Jonathan Phillips. Earlier reports from this lab describe an instrument which can be built with readily available equipment [54,57,58]. However, the instrument described earlier suffered from several limitations.…”

Microcalorimetric studies of the structure of supported bimetallic catalyst particles

“…This last result is not surprising given that only on the weakly interacting support did a true surface alloy form. Calorimetric, XRD, TEM and MES studies of graphite supported iron-iridium [33], and iron palladium [34,35] were also carried out. In each equimolar metal case calorimetric studies of oxygen adsorption revealed that the surface was primarily metallic iron after a low temperature reduction and a bulk alloy after a high temperature reduction.…”