National Physical Laboratory

Interfacial Chemistry and Catalysis

Catalysis is a cornerstone of global industrialisation, most notably in chemicals production and energy conversion technologies, and is central to the world's sustainable economic growth. Despite the success of these sectors, there is an ever-growing need to develop improved catalysts with better efficiency and selectivity in order to support more environmentally friendly and economically viable chemistry in industry.

Rational catalyst design and optimisation relies upon a detailed fundamental understanding of structure-activity relationships. In particular, our ability to identify active sites at reacting catalyst surfaces is key to the development of new catalytic materials with tailored properties. Such information can only be gleaned through in situ or in operando characterisation, wherein determination of physicochemical properties is undertaken under relevant reaction conditions. Furthermore, catalysts exhibit significant degrees of spatial heterogeneity, so localised information is also critical. Hence, there is a recognised need for new measurement science.

To address the growing industrial need, our vision at NPL is to develop a toolkit of state-of-the-art catalyst characterisation techniques enabling a holistic understanding of catalyst behaviour through bulk and local structural, chemical and activity measurements. Our focus is on catalytic processes at solid-liquid interfaces, notably supported metal nanoparticles with the following primary applications:

  • Electrocatalysis
    • Hydrogen fuel cells (hydrogen oxidation, oxygen reduction)
    • Electrolysers (hydrogen and oxygen evolution)
  • Heterogeneous Catalysis
    • Selective hydrogenation (e.g. for fine chemicals and pharmaceuticals)
    • Glycerol oxidation (e.g. for biomass conversion)

Our cutting-edge measurement capability is centred around the development of two approaches to interfacial characterisation: multi-scale electrochemical imaging and molecular spectroscopy.

In addition, we have a broad range of traditional electrochemical techniques and complementary materials characterisation.

Catalysis - Fig 1


Electrochemical Imaging

We have established a capability in Scanning Electrochemical Microscopy (SECM), which can be used to measure the distribution of electrocatalytic activity across solid-liquid interfaces. This includes mapping hydrogen oxidation, oxygen reduction and hydrogen peroxide generation activity over various length scales, ranging from microarray screening to individual nanoparticle imaging.

More information on Electrochemical Imaging


Molecular Spectroscopy

Our current projects involve adding chemical information to interfacial activity measurements through molecular spectroscopies, namely Fourier transform infrared (FTIR) spectroscopy and Raman nanospectroscopy:

FTIR Spectroscopy

Catalysis - Fig 2

We employ FTIR spectroscopy in the attenuated total reflection (ATR) mode to characterise catalysts and their interfacial adsorbates in the presence of liquid reagents. Specific capabilities include:

  • Accessories for single and multi-reflection ATR at variable angles
  • Flow cell for ATR-FTIR at elevated temperatures (up to 120 ºC)
  • Flow cell for Electrochemical-ATR-FTIR measurements
Catalysis - Fig 3

Raman Nanospectroscopy

We work closely with NPL's Surface & Nanoanalysis Group in the development and application of Raman spectroscopy to characterising catalytic interfaces. In particular, we are developing near-field Raman mapping capabilities using tip-enhanced Raman scattering (TERS) to enable chemical imaging of dynamic catalytic systems at the nanoscale

Atomistic Modelling

Also supporting our facility in molecular spectroscopy is an emerging capability in atomistic modelling. In particular, we use DFT modelling to facilitate the interpretation of spectroscopic data and we are currently developing a molecular dynamics simulation with the aim of modelling interfacial reactions.


Publications


Complementary Techniques

NPL also has a suite of instrumentation and expertise in a range of techniques that support the catalyst metrology theme.

Imaging:

  • Atomic Force Microscopy (AFM) and conducting-AFM
  • Tip Enhanced Raman Spectroscopy (TERS)
  • Scanning Kelvin Probe Microscopy (SKPM)
  • Scanning Electron Microscopy (SEM)

Chemical/Physical Characterisation:

  • Energy Dispersive X-ray Spectroscopy (EDX)
  • Electron Backscatter Diffraction (EBSD)
  • Bulk Raman Spectroscopy
  • X-ray/Ultraviolet Photoelectron Spectroscopy (XPS/UPS)
  • Secondary Ion Mass Spectrometry (SIMS)
  • Brunauer, Emmett Teller (BET) Surface Area Analysis


People


External Collaboration

We collaborate widely on developing and applying the above techniques, both within NPL and externally with academia and industry.

Last Updated: 26 Apr 2017
Created: 5 Jan 2012

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