A well-defined supported Pt nanoparticle catalyst for heterogeneous catalytic surface science

Abstract

Our ability to rationalise the activity of heterogeneous catalytic materials relies on a precise understanding of both the structure and composition of the catalyst under reaction conditions to resolve active sites. Their highly dynamic nature means that catalysis suffers from an observer effect, where the act of measuring activity and/or structure will modify the structure itself. Herein, we present a well-defined catalyst consisting of 2 nm Pt nanoparticles supported on SiO₂ that can be dynamically modified and regenerated without irreversibly changing the underlying structure or activity of the catalyst. Using in situ diffuse reflectance infrared Fourier transform spectroscopy and transmission electron microscopy we identify that the catalyst is resistant to oxidative and reductive treatments, but irreversibly restructures in reactive environments (CO + O₂) at moderate pressures and temperatures. We show that by using transient pressure pulse experiments it is possible to minimise the restructuring in reactive environments, which when coupled with kinetic modelling can be used to identify site and state dependent activity while simultaneously quantifying the number of active sites. The well-defined nature of this 2 nm Pt/SiO₂ catalyst means it can be utilised to gain molecular insight into catalytic processes and act as a new material for use in heterogeneous catalytic surface science. Further, the rapid restructuring of the catalyst during CO oxidation demonstrates that it is not a benign characterisation tool for comparison of catalysts.