Application of aerosol techniques to study the catalytic formation of methane on gasborne nickel nanoparticles

"Aerosol catalysis" is shown to be a powerful tool for investigating the ca talytic properties of freshly formed nanoparticles in situ and without subs trate interference. The method is first outlined conceptually, followed by an illustrative application to the catalytic formation of methane on a nick el nanoaerosol. Reaction order and activation energy were found conform wit h generally accepted values from supported Ni catalysts. The TOR decreases strongly during the first 10's as the reaction proceeeds toward a steady va lue. The decrease correlates with a buildup of about 0.3 monolayer equivale nts of carbon on the particle surface measured by TGA and a decline in part icle photoelectric activity observed via measurement by aerosol photoemissi on spectroscopy (APES). APES is shown to be capable of detecting the progre ssive degradation of the freshly formed particle surface due to a heterogen eous surface reaction on a millisecond time scale. Furthermore, it was poss ible to induce order-of-magnitude changes in TOR via defined changes in par ticle morphology, induced by aerosol restructuring techniques preceding exp osure to the catalytic reaction.