High temporal resolution TEM imaging of dynamic processes in heterogenous catalysts

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The overall aim of this project is to study changes in metallic and other nanoparticles involved in heterogeneous catalysis at ms timescales on order to probe transient structural changes. This project will use recent developments in fast direct electron detectors for transmission electron microscopy to achieve the necessary timing resolution. The potential impact of these studies is a better understanding of catalytic processes of interest to the industrial sponsor including automotive exhaust emissions, Fischer Tropsch catalysts and electrocatalysis in fuel cells and related systems. Initially the project will use new detectors operating at kHz frame rates to record the dynamic changes as catalysts evolve as a function of time and temperature giving particular insights into the early stages of catalyst activation and subsequent poisoning and deactivation. A key aim is to "handshake" the temporal resolutions accessible through molecular dynamics calculations and related computational simulations with those available experimentally. If this can be achieved it will potentially enable local nanoscale studies of the chemical kinetics of complex systems based on real space image data. An additional aim is to develop the use of machine learning based on convolution neural networks to develop image analysis tools suitable for analysing large data sets containing millions of images. In particular it will be necessary to develop automated approaches, similar to those used in structural biology to identify and classify significant numbers of nanoparticles in order to obtain reasonable statistics from heterogeneous ensembles. The research proposed relies heavily on unique instrumentation available at the electron Physical Sciences Imaging Centre. Specifically a new high speed direct electron detector operating at a frame rate in excess of 2KHz in 12 bit counting mode will be used to acquire time series data and the availability of both heating and in-situ gas reaction cells will facilitate studies of model catalyst systems under close to in-operando conditions. Within all of the above aims and objectives it will be necessary to ensure that the methods developed are robust to low dose data acquisition to ensure that electron beam induced effects are minimised. The final aim of the project will be to extend the methodologies developed to micron timescales. This will involve the use of a new time resolved TEM, unique in the UK currently under design and construction and due for delivery to the Rosalind Franklin Institute in 2020. The project falls within the EPSRC energy and physical sciences research areas The project is funded by Johnson Matthey plc through the iCase initiative