Simultaneous in situ SEM and STEM analysis of gas/catalyst reaction in a cold field-emission environmental TEM

The ability to simultaneously observe surface and bulk changes at the nanometerscale is much desired in materials research. We describe a simultaneous in-situ SEM/ STEM study of the Pt/C electrocatalyst for polymer electrolyte fuel cells in a gaseous atmosphere, which was carried out using a Hitachi HF 3300 60-300 kV cold-FEG TEM equipped with SEM and STEM imaging capability. A gas injection-heating holder is used in simulating an accelerated degradation by heating the Pt/C powderin 4 Pa of humid air at 200oC. Pt particles on the carbon support were agglomerated, and gradually penetrated into the carbon support. At the end, most of the Pt particles had burrowed into the carbon support and the surface of the carbon support became porous. The loss of Pt particles on the surface of carbon support leads to the degradation of Pt/C electrocatalyst. This study has demonstrated that invaluable surface information can be easily obtained from adding surface imaging ability to a