Sn/Pt纳米立方体对乙醇电催化氧化的原位FTIR光谱研究

Electrochemical and Spectroscopic Studies of Ethanol Oxidation on Nano-Cubic Pt Modified by Tin Adatoms

采用循环伏安电沉积方法制备了Sn修饰的铂纳米立方体,并研究其对乙醇的电催化氧化.结合传统的电化学方法和原位电化学红外光谱技术研究了Sn的作用机理.循环伏安研究表明,Sn修饰后使其对乙醇氧化的起始电位显著负移,Sn覆盖度～0.90时乙醇氧化的起始电位为-0.1 V.原位红外光谱结果表明,修饰Sn后极大地促进了乙酸的生成,更利于乙醇的直接氧化途径,但对乙醇的C—C键断裂促进作用不大.

The nano-cubic Pt modified by tin （Sn） was synthesized and used to investigate the role of this adatom played in the ethanol oxidation. The onset potential of ethanol oxidation was significantly shifted negatively which can be forward about 300 mV when the coverage of Sn （θSn） was 0.9. The electrtocbemical in situ FTIR result demonstrated that the amount of CO2 increased first, and then decreased with θSn increased, and reached the maximun when θSn was 0.38. Furthermore, the formation of acetic acid could be observed at very low potential （-0.05 V） after modifying Sn adatom, and the amount of acetic acid increased with θSn increased. That is, Sn deposited on Pt surfaces has a double effect on the ethanol oxidation. First, it facilitates the oxidation of CO coming from the cleavage of the C--C bond in ethanol by a bifunctiontal mechanism. Second, the Pt-Sn ensemble catalyzes the oxidation of ethanol to acetic acid. This means that the main product in the oxidation of ethanol for the Pt-Sn system should be acetic acid unless the Pt surface structure has some special sites able to break the C--C bond.