In Situ TEM Study of the Genesis of Supported Nickel Catalysts

Abstract

In situ transmission electron microscopy is a powerful technique with the unique ability to temporally and spatially resolve nanoscale processes. This can be leveraged in order to obtain insight into the timescales of phenomena occurring during particle growth during the preparation of supported metal catalysts. Thanks to careful experimental design and comparison with ex situ results, the growth of individual nickel nanoparticles from a nickel phyllosilicate catalyst precursor during reduction was studied in situ under atmospheric pressure of 5% H2/Ar at 500 °C and modeled with first-order reaction kinetics. Particles grew rapidly, reaching a final size of between 3.5 and 7 nm within 3-4 min. The vast majority of particles grow as immobile single particles. A two-step particle growth mechanism was sometimes observed wherein two particles nucleating sufficiently close to one another sintered. The resulting particles were not significantly larger (5-7 nm) than those that did not undergo this sintering process. This finding supports the hypothesis that the size of the region from which the nickel species originated determined the particle size.