Promotion of PdCu/C Catalysts for Ethanol Oxidation in Alkaline Solution by SnO2 Modifier

• Published in: ChemCatChem 2012-08, Vol.4 (8), p.1154-1161
• Main Authors: Wang, Kuan-Wen, Kang, Wei-Da, Wei, Yu-Chen, Liu, Chen-Wei, Su, Pai-Cheng, Chen, Hung-Shuo, Chung, Shu-Ru
• Format: Article
• Language: English
• Subjects: alloys; Oxidation; palladium; Spectrum analysis; supported catalysts; tin
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201100500

The development of high performance PdCu/C catalysts through manipulation of reduction temperatures and addition of SnO2 promoter has been elucidated systematically in order to enhance ethanol oxidation reaction (EOR) performance. The structure, morphology, surface species, and electroactivity of the PdCu/C and SnO2‐modified PdCu/C catalysts are characterized by use of X‐ray diffraction, high resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and cyclic voltammetry. For the PdCu/C catalysts, the ratio of the forward anodic peak current density to that of the reverse, that is, the If/Ib ratio, the degree of alloying (Dalloy), grain size, and EOR performance increases as the reduction temperature increases to 570 K. However, severe sintering at 670 K deteriorates EOR performance. Therefore, 570 K is a suitable reduction temperature for the preparation of PdCu/C catalysts with fine alloy structure, small crystal size, good Dalloy, good anti‐poisoning ability, and excellent EOR performance. For the SnO2 modified PdCu/C catalysts, addition of 20 wt % Sn may cause a large amount of SnO2 to form on the surface and block the active site of the catalysts, thus decreasing EOR performance. However, addition of 10 wt % Sn promotes stability in EOR performance, attributable to the significant amount of PdSn phase in the bulk and SnO2 species on the surface, which enhance the CO oxidation ability and electrochemical surface area. Consequently, based on the chronoamperometric measurements after 1 hr, the EOR activity of PdCu/C catalysts with 10 wt % SnO2 modification is enhanced by approximately 230 % compared with the as‐reduced sample. Giving more than 100 %: In the presence of a PdSn phase and surface SnO2, the EOR activity of catalyst PdCuSn10 (10 wt % SnO2 addition) is enhanced to 230 % of that of PdCu/C, as evidenced by chronoamperometric measurements. This is attributable to the significant amount of PdSn phase in the bulk and SnO2 species on the surface, which enhance the CO oxidation ability and electrochemical surface area.