PdAu/C catalysts prepared by plasma sputtering for the electro-oxidation of glycerol
Co-sputtered Pd0.7Au0.3 catalyst and alternate sputtered Pd0.35Au0.3Pd0.35 and Au0.15Pd0.7Au0.15 materials were prepared by plasma deposition of Au and Pd atoms on a carbon diffusion layer. Atomic composition and metal loadings were evaluated from EDX and RBS, respectively. The low amount of metal deposited and the resulting low metallic film thickness made TEM and XRD characterizations difficult to perform, therefore, catalyst microstructures and surface compositions were determined from electrochemical methods and compared with data obtained with Pd/C, Au/C and Pd0.7Au0.3/C materials synthesized via the “water in oil” microemulsion method. The surfaces of co-sputtered Pd0.7Au0.3 and alternate sputtered Pd0.35Au0.3Pd0.35 and Au0.15Pd0.7Au0.35 materials are partly composed by PdAu alloy. The plasma sputtering method leads to more active bimetallic PdAu material than the wet chemistry method. Modification of palladium surface by gold atoms leads to increase the catalytic activity toward glycerol electrooxidation. The PdAu surface alloy composition has no significant effect on the catalytic activity, however, the presence of non-alloyed gold sites on the material surface leads to the enhancement of the catalytic activity. The mechanism seems to involve glycerol adsorption on palladium surface and hydroxyl species formation on gold surface leading to catalytic activity enhancement through the bifunctional mechanism.
Graphical abstract(a) Cyclic voltammograms of the co-sputtered Pd0.7Au0.3 catalyst, and of the 3-layer alternate sputtered Pd0.35Au0.3Pd0.35 and Au0.15Pd0.7Au0.15 catalysts. (b) Polarization curves of glycerol oxidation recorded (a) on sputtered Pd1 and Au1, co-sputtered Pd0.7Au0.3 and wet chemistry Pd0.7Au0.3/C catalysts, and (b) on co-sputtered Pd0.7Au0.3, wet chemistry Pd0.7Au0.3/C, and alternate sputtered Pd0.35Au0.3Pd0.35 and Au0.15Pd0.3Au0.15 catalysts (v = 20 mV s−1, N2-saturated 1.0 M NaOH electrolyte, T = 293 K).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Plasma sputtered PdAu is more active than wet chemistry PdAu. ► Modification of Pd by Au increases the catalytic activity of glycerol oxidation. ► PdAu surface alloy composition has no significant effect on catalytic activity. ► Presence of non-alloyed surface Au sites enhances the catalytic activity.
Journal: Applied Catalysis B: Environmental - Volume 107, Issues 3–4, 21 September 2011, Pages 372–379