Size Effect of Platinum Nanoparticle Catalyst on Methane Oxidation Reaction

Catalytic methane oxidation has attracted considerable research interest in energy generation and production of more valuable chemicals, such as methanol and acetic acid. Platinum nanoparticle catalysts have been mostly used for their higher activity than other metals in the reaction. However even with Pt, high reaction temperature is often required to activate methane oxidation. For example, the onset temperature of methane oxidation using Pt catalyst is typically above 600 K. Because a decrease in the reaction temperature has apparent advantages in improving energy utilization efficiency and better controlling the reaction extent, catalytic methane oxidation at low temperature is desired.  

We study the size effect of Pt nanoparticles on catalytic methane oxidation by preparing Pt/SiO₂ samples with different particle sizes, ranging from below 1 nm to around 7 nm, and studying their catalytic property. The experimental results show a strong size dependency of the catalytic property. The catalysts containing bigger Pt particles have significantly lower onset reaction temperature and decreased activation energy. Kinetic experiments using a packed bed reactor and mechanistic studies using in situ Fourier transform infrared spectroscopy are conducted to investigate the size effect, which is attributed to changes in the electronic structure and consequently in the surface status of the catalysts.