Electrocatalyst synergistic effects

Zellner MB, Chen JG (2005) Potential Application of tungsten carbides as electrocatalysts synergistic effect by supporting Pt on C/W(l 10) for the reactions of methanol, water, and CO. J Electrochem Soc 152 A1483-A1494... 

Electronic interaction and synergistic effects between catalysts and the support material have been investigated in the context of fuel-cell electrocatalysts. Electron spin resonance (ESR) has been used to demonstrate the electron donation by Pt to carbon [11] support. This has been further supported by XPS studies [12], which show that the metal acts as an electron donor to the support, their interaction depending on their respective Eermi levels. Bogotsky and Snudkin [13] have shown that the characteristics of the electrical double layer formed between the microdeposit (Pt) and the support depends to a certain extent on the difference in the work function of Pt (5.4 eV) and carbon support (pyrolytic support 4.7 eV), thereby resulting in an increase of the electron density of Pt. However, the rise in the electron density can be significant only when the particle size of the microdeposit is comparable to the thickness of the double layer. 

The synergistic effect between Pt and WC was demonstrated with Pt/WC powder catalysts. Thus, 7.5 wt% PtA 2C led to high specific activity of 156 mA/cm at 0.75 V (vs Ag/AgCl) in half cell test for methanol oxidation without Ru, which was commonly used with Pt for DMFC anodes (33). This specific activity represents higher electroactivity than that of commercial Pt-Ru/C electrocatalyst (20 wt% PtRu/C, E-Tek) imder the same experimental condition. Further improvement in the activity of methanol oxidation was observed when W2C was prepared to contain mesopores (34). There is also a report that 20 wt% Pt(W2C electrocatalysts show a higher mass current density (mA/mgpt) than 20 wt% Pt(C at the same potential under 0.5 M H2SO4 electrolyte, SCE reference electrode (155). 

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