Investigation of grain boundary formation in PtRu/C catalyst obtained in a polyol process with post-treatment

The grain boundary formation in PtRu/C catalyst obtained in a polyol process with post-treatment was investigated by scanning transmission electron microscopy, transmission electron microscopy (TEM) and High resolution TEM. The crystalline structure and surface composition of the PtRu/C catalysts were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical activities were evaluated by CO stripping voltammetry and linear sweep voltammetry measurements in combination with in situ IR reflection-absorption spectroscopy. As-prepared isolated spherical nanoparticles on the carbon support started to interconnect after washing procedure, and the interconnection between the particles was greatly promoted by reduction post-treatment at 80 °C; grain boundary formation occurred in the interconnected particles with increasing reduction temperature to 200 °C, and the particles reconstructed severely with further increasing reduction temperature to 400 °C. The defects at the grain boundary served as active sites for methanol electro-oxidation by weakening COads adsorption on Pt sites and facilitating OHads formation, and the PtRu/C catalyst treated in 5% H2/Ar at 200 °C for 10 h had the greatest catalytic activity for methanol electro-oxidation among the PtRu/C catalysts treated under various atmospheres and temperatures.