Pt_xSn_y/C催化剂对DEFCs中乙醇电氧化活性的研究

Investigation on Pt_xSn_y/C activity to ethanol electrooxidation in direct ethanol fuel cells

通过脉冲微波辅助的多元醇还原技术快速合成了不同Pt/Sn原子比、粒径小且分布窄的PtxSny/C(x∶y=2∶1,3∶2,和1∶1)催化剂,对之进行了XRD和TEM等物化表征,并采用循环伏安技术研究了不同温度下PtxSny/C对乙醇以及其氧化中间产物乙醛和乙酸的电催化活性。对于乙醇的电氧化过程,Sn的掺杂量与反应温度均会影响Pt的催化活性。低温时,贫Sn催化剂的性能较好,而在高温时,富Sn催化剂的性能更好,这归因于Sn含量可能影响催化剂表面含氧基团,晶格常数,欧姆效应等。对于乙醛的电氧化过程,在任何温度下,Pt1Sn1/C的催化活性均最高,因为Sn的存在可有效移除C2物种在Pt上的吸附,而且通过提供含氧基团能抑制催化剂毒物的形成。在乙酸的电氧化过程中,PtxSny/C催化剂上可检测到微弱电流,这表明Sn在活化C-C键,将乙酸氧化为C1化合物中能起到一定的作用。

PtxSny/C series catalysts with different atomic ratio （x∶y=2∶1,3∶2,and 1∶1） were fast synthesized with small particle size （～3 nm） and well dispersion by using pulse microwave assisted polyol method. The physico-chemical characteristics were determined by XRD and TEM. In order to investigate PtSn＇s activity to ethanol electrooxidation,the electrochemical evaluation was applied to the electrooxidation of ethanol and its main by-products including acetaldehyde and acetic acid at different temperatures. For ethanol electrooxidation,the Sn addition can improve Pt＇s ability with different contributing effect depending on Sn content and temperatures. At lower temperature,Sn-poor catalysts exhibited better performance while Sn-rich catalysts gave improved performance at higher temperature,which is probably related to surface oxygen-containing species,lattice parameters,and ohmic effect dependent on Sn content. From the acetaldehyde electrooxidation results,Pt1Sn1/C showed the highest activity at all the investigated temperatures. This could be contributed to that Sn existence can effectively remove C2 species and inhibit the poison formation by supplying oxygen-containing species. Moreover,in the case of acetic acid electrooxidation,over PtxSny/C catalysts,there was small current produced,giving an indicator that Sn does take effect on the activation of C-C bond,and in this way help the oxidation of acetic acid to C1 species.