催化剂制备方法及高温还原对Pt/C/FN疏水催化剂活性的影响

Effect of fabrication method of Pt/C catalyst and high temperature reduction on catalytic activities of hydrophobic Pt/C/FN catalysts

采用常规浸渍还原法、改进浸渍还原法和高压微波加热法分别制备20%Pt/C催化剂,用X射线衍射(XRD)、透射电镜(TEM)和X射线光电子能谱(XPS)对催化剂表征。三种方法制备的催化剂Pt粒径分别为2.9、2.0和1.9nm,标准差分别为0.8、0.7和0.5nm,高压微波加热法和改进浸渍还原法催化剂中Pt(0)含量分别为40.9%和43.3%。对高压微波加热法催化剂用H2/N2混合气300℃还原处理2h,或500℃处理1h,Pt粒径分别增至2.2和2.1nm,Pt(0)含量分别增至44.3%和49.7%。将Pt/C催化剂与聚四氟乙烯一起负载于泡沫镍(FN)载体,制备Pt/C/FN疏水催化剂,考察其对氢水液相交换反应的催化活性。影响疏水催化剂活性的因素包括Pt粒径大小及Pt(0)含量,降低Pt/C催化剂上Pt粒径大小,或提高Pt单质含量,均可提高疏水催化剂活性。

Pt/C catalysts were prepared by conventional and improved impregnation-reduction method, or microwave heating method. Transmission electron microscopy analyses indicated that average sizes of Pt particles by the three methods were （2.9±0.8） nm, （2.0±0.7） nm and （1.9±0.5） nm, respectively. X-ray photoelectron spectroscopy measurements revealed that the Pt（0） contents of the Pt/C catalysts by microwave heating method and improved impregnation-reduction method are 40.9% and 43.3%, respectively. The Pt/C catalysts obtained by microwave heating method were reduced by H2/N2 mixed gas in 300℃ for 2 h, or 500℃ for 1 h. The average sizes of Pt particles increase to 2.2 and 2.1 nm, and the Pt（0） contents increase to 44.3% and 49.7%, respectively. The polytetrafluoroethylene and Pt/C catalysts were supported on foamed nickel （FN） to obtain hydrophobic Pt/C/FN catalysts, and the catalytic activities of the hydrophobic catalysts were investigated for hydrogen-water liquid phase exchange reaction. The average size of Pt particles and the Pt（0） content have influences on the catalytic activity of the Pt/C/FN catalyst. The increased dispersion of Pt particles or Pt（0） contents increases catalytic activities of the hydrophobic catalysts.