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European Microscopy Congress 2020 Abstract Database

Investigating porosity and catalytic activity of platinum nanoparticles

Investigating porosity and catalytic activity of platinum nanoparticles

Session

PSA.5 - Nanoparticles & Catalysts

Authors

Dr Neil Young (1), Dr Christopher Batchelor-McAuley (1), Miss Wenmiao Yu (1), Dr Xin Chang (1), Prof Richard Compton (1)

Affiliations

1. University of Oxford

Keywords

Catalyst

Nanoparticle  

Porosity

STEM

Abstract text

Mesoporous nanoparticle structures commonly arise in both model and commercially viable catalytically active materials.  Porous nanoparticles exhibit high total surface areas both internally and across the particle surface.  Progress in enhancing catalytic function and selectivity is possible through intelligent design of the catalyst material via an understanding of the level of porosity and also accessibility of the catalytic interface or ‘active-sites’. Characterisation of porosity remains challenging and our work seeks to add to this area of understanding.  In the current study we apply combined structural characterisation via transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), in addition to single-particle electrochemical measurements to elucidate catalytic activity.  A range of commercially available porous platinum nanoparticles are studied and reaction rates for two chemical reactions are reported for each available nanoparticle population in the size range 30nm to 70nm.  High-resolution TEM is used to study the nanoparticle morphology which is found to correspond to an aggregate of numerous highly-ordered single-crystalline seed particles [1].  High-angle annular dark field (HAADF) STEM is used to gain insight into the level of porosity across the size range of platinum nanoparticles.  Through comparison of image intensity in this HAADF-STEM imaging mode the porous particles are compared to solid spherical platinum particles, giving insight into the relative densities of the two families of platinum nanoparticle.  On average the density of porous particles is 70% of the density of similarly sized solid spherical platinum particles [2].  The density of the porous particles does not vary significantly as a function of size.  Our on-going work seeks to utilise the binding of molecules to the active sites within porous particles, and subsequent physical and chemical characterisation to better understand the real-world ‘active-site’ density within the particles [3].   

References

[1] W. Yu et al, Nanoscale 11 (2019) 17791

[2] W. Yu et al, PCCP 21 (2019) 20415

[3] The authors acknowledge use of characterisation facilities within the David Cockayne Centre for  Electron  Microscopy,  Department  of  Materials,  University  of  Oxford,  alongside financial support provided by the Henry Royce Institute (Grant ref EP/R010145/1).