Palladium surface roughness

AFM can be used to study the surface morphology of a membrane. Varma s group [31] appeared to be the first one to use AFM to measure the surface roughness to characterize the differences between conventional electroless plating and electroless plating assisted by osmotic pressure of a thin palladium layer supported on Vycor glass surface. AFM was also used to characterize the oxidized Pd surface [32, 33]. 

Microstructural analysis using SEM is requisite for examining surface details and features such as film pore structure and thickness or the crystallites formed by the EP surface activation process [81, 186]. AEM can be used to probe micro- to nanoscale surface topography and determine critical parameters such as surface roughness, (arithmetical mean deviation of the profile) [70, 154, 187] or the size and distribution of surface activation particles [188]. Nanoparticles formed during surface activation [147, 189] and the dislocation substructure of palladium [90] have been studied by TEM. Optical or laser profilometry is used to quantify surface roughness or to measure film thickness on a flat surface [190]. 

The main factors determining the prevalence of the n form are therefore (i) degree of occupancy of the d-orbitals, (ii) temperature, (iii) surface roughness, and (iv) surface coverage, and (v) some quality specific to palladium, on which it is distinctly more favoured than on platinum. This last point will be reverted to later. 

A few additional points have also been raised by specific surface-science work concerning the catalytic reduction of NO. For instance, it has been widely recognized that the reaction is sensitive to the structure of the catalytic surface. It was determined that rough surfaces such as (110), or even (100), planes enhance NO dissociation over flatter (111) surfaces, and also favor N2 desorption instead of N20 production. On the other hand, NO dissociation leads to poisoning by the resulting atomic species, hence the faster reaction rates seen with medium-size vs. larger particles on model rhodium supported catalyst (the opposite appears to be true on palladium). Also, at least in the case of palladium, the formation of an isocyanate (-NCO) intermediate was identified... 

Schematic representation of two sets of electrodes of palladium (a) and textile electrode (b) and the influence of roughness of the electrode surface on the measured impedance (Z). 

It should be taken into account that this is only valid for the textile electrode investigated in this work, because this parameter is also dependent on the roughness of the surface. The roughness is definitely the cause of this edge effect, because it is absent when using smooth palladium electrodes. 

In this section, the distance between the electrodes is studied for different electrolyte concentrations and distances between the electrodes at a constant electrode surface area of A = 180 mm2. The obtained impedances are plotted logarithmically against the distance between the electrodes (d) as shown in Fig. 9.14. Relationships obtained for the textile electrodes are identical to those for the palladium electrodes if the smallest distance between the electrodes is not taken into account. Additionally in this case, the roughness of the textile electrodes is responsible for this effect and can be neglected for distances longer than d=40mm - an effect that increases with decreasing distance between the electrodes. Of course, also in this case,... 

In the following section, CO adsorption on alumina supported palladium nanoparticles of various sizes and surface structures is examined and compared with the corresponding results for CO on Pd(l 11) and rough Pd(l 11) (119,120,152,289). The preparation and characterization of the alumina support and of deposited palladium nanoparticles have been described in detail (63,68,73,83,101,290) and only a brief summary is given here. 

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