The Effect of the Nano and Microstructure of PtRu/C Electrocatalysts Towards Methanol and Carbon Monoxide Oxidation
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The Effect of the Nano and Microstructure of PtRu/C Electrocatalysts Towards Methanol and Carbon Monoxide Oxidation Wataru Sugimoto, Tomoyuki Kawaguchi, Yasushi Murakami, and Yoshio Takasu Department of Fine Materials Engineering, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, JAPAN ABSTRACT Nanoparticulate Pt50Ru50 supported on a carbon black (CB) were prepared by an impregnation method and the effect of the nano and microstructure towards the electrocatalytic oxidation of methanol and carbon monoxide were evaluated. The in-house prepared PtRu nanoparticles were well-alloyed and finely dispersed on CB, as revealed by XRD and FESEM. FESTEM-EDX analysis of isolated PtRu single nanoparticles indicated that although the majority of the binary particles had a metal composition in accordance to the nominal ratio, some compositional deviation was observed. The activity towards electrocatalytic oxidation of methanol and preadsorbed carbon monoxide is discussed based on the nano and microstructure. INTRODUCTION Carbon supported PtRu alloys are one of the most promising anode electrocatalysts for DMFC (Direct Methanol Fuel Cell) application. Numerous investigations on the anodic characteristics of PtRu/C electrocatalysts have so far been conducted.1-6) In order to increase the utilization of the precious metal, many factors which should effect the electrocatalytic oxidation of methanol must be elucidated. The influence of the homogeneity, the particle size, the bulk/surface composition of the PtRu alloy nanoparticles towards the electrocatalytic oxidation of methanol are just some of the issues that need to be clarified. In order to examine these effects, the extent of bimetal alloying, particle size, etc. must be controlled, and the evaluation of the composition and crystal structure of PtRu/C electrocatalysts on the nanoscopic level are inevitable. We have previously reported that well alloyed and highly active PtRu/C electrocatalysts can be prepared by a simple impregnation method using chlorine-free precursors such as In this study, the nanoscopic and microscopic Pt(NO2)2(NH3)2 and Ru(NO)(NO3)x.7-9) characteristics of PtRu/C electrocatalysts were evaluated and their relation to the electrocatalytic oxidation of methanol and preadsorbed carbon monoxide was studied.
EXPERIMENTAL Carbon supported PtRu electrocatalysts were prepared by an impregnation method using carbon black (Mitsubishi Chemicals CBB; SBET=200 m2 g-1) as the support and ethanolic The alloy composition solutions of Pt(NO2)2(NH3)2 and Ru(NO)(NO3)x as metal precursors. used was Pt50Ru50, (Pt/Ru = 50/50 (mole/mole)) and the metal loading was 30 mass%.
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Pyrolysis was conducted under a continuous flow of H2(10%) + N2(90%) at 150, 200, 300, and 450°C for 2 h. The bulk crystal structure and microscopic features of the PtRu nanoparticles were characterized using X-ray Diffraction (XRD) and Field Emission-Scanning Electron Microscopy (FE-SEM). The nanoscopic composition of single PtRu nanopartic
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