In situ observation of catalytic CeO2-nanocube (100) surface with carbon contamination by environmental TEM : A model for soot combustion

An environmental transmission electron microscopy (ETEM) was applied to the in situ observation of carbon contamination removal reaction on (100) crystal plane of catalytic CeO2 nanocubes. The distance between the surface of CeO2 and carbon layer (width) was quantatively measured versus time at eleven points on three CeO2 nanocubes by observation at oxygen pressure of 3.0×10−1 Pa at 400 oC. The carbon contamination removal rate in the time range of 100 to 460 s was 0.01±0.002 nm s-1, not depending on the place. However, in the later stage the rates of 0.057±0.01 nm s-1 and 0.24±0.02 nm s-1 were obtained for carbon contamination of different area in specimen even if the same crystal plane (100) was of contact with carbon. Regarding with rate, crystal plane in inner area of aggregate become faster and made carbon eliminate more quickly. The result means that the local-environmental influence in nanoparticle aggregates is taken account in heterogeneous catalytic reaction as well as contamination reduction using ETEM.