Chemical Engineering Seminar Series : Prof. Samji Samira

Navigating convoluted catalytic structures for enhanced activity, selectivity, and stability

All pathways towards net zero emissions in the 21st century will involve a transition from the use of fossil-based resources for process energy to renewable electricity.  In the context of this transition, electron and photon driven chemistries offer a versatile toolkit by accessing redox and excited state transformations.  At the core of these radical technologies is the rational design and development of heterogeneous catalysts that drive relevant transformations.  This gives rise to the need for the identification of chemical and physical properties of active site environments that describe not just their activity, but also their selectivity and stability.

In this seminar, I will first discuss a systematic approach to identify empirically measurable chemical and physical properties of active site environments in working catalysts that govern not just their electrocatalytic activity, but also selectivity and stability.  This will be showcased for perovskite oxide electrocatalysts using electrochemical oxygen reduction (ORR) – key bottleneck reaction for the use of hydrogen – as a probe reaction.  The effect of the average surface metal-oxygen bond strength in the perovskite oxides and its overall electrocatalytic performance will be discussed.  The use of such empirically measurable properties of working, non-model catalytic centers to identify optimal electrocatalysts will be showcased.  Second, I will discuss strategies to engineer transient charge transfer at the metal–adsorbate interface using visible photons as an energy source.  The use of visible photon flux on controlling the surface coverages of CO on Pt nanoparticle surfaces and their implications on reactivity will be discussed.  The ideas towards rational electro- and photocatalytic design that I will discuss here, can be leveraged to steer new pathways towards reactivity, selectivity, and stability for the direct use of renewable electricity in energy conversion and chemical manufacturing.