Catalysts are the hidden workhorses of chemistry in society: widely used in industry, they help reduce energy consumption, minimize pollution, synthesize chemicals, and produce food. They accomplish all of these by lowering the activation energy barriers for desired reaction pathways, resulting in more efficient chemical reactions.

 

Activation Barrier

 

Today, we still know very little about how these reactions proceed. For example, the catalytic converter in automobiles was developed to convert harmful exhaust gases, such as carbon monoxide (CO) and nitric oxides (NOx), into less harmful or inert gases, such as carbon dioxide (CO2), oxygen gas (O2), and nitrogen gas (N2). The catalytic converter was developed through empirical data, instead of a fundamental understanding of the chemical reactions involved.

 

drawing

One reason why chemical reactions are poorly understood on metal catalysts is that during reaction conditions, numerous individual reactions can occur simultaneously on the surface of the catalyst, each at different stages along the reaction pathway. Projects in the LaRue Catalysis Research Lab are aimed at isolating specific steps of the reaction pathway in order to understand the most fundamental processes that occur during these important chemical reactions.

 

drawing

 

Current projects involve using Raman spectroscopy, x-ray spectroscopies, and ultrafast spectroscopies to probe the elementary steps of chemical reactions with the goal of learning how to create more efficient catalysts for the challenges of tomorrow.

 

Raman Spectroscopy

Raman spectroscopy is a technique that uses the inelastic scattering of light to provide information about bond energies for the reactants, intermediates, and products involved during chemical reactions.

 

drawing

 

drawing

 

X-ray Spectroscopies

X-ray spectroscopies, such as x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), and x-ray photoelectron spectroscopy (XAS), provide element and chemically sensitive information about the atoms involved during chemical reactions.

 

XAS-XES

 

Ultrafast Spectroscopies

Femtosecond lasers can be used probe reactions on ultrafast timescales (10E-15 seconds). In these techniques, a femtosecond laser is used to pump (excite) a chemical reaction on a catalyst all at once. Time-resolved snapshots of specific processes can then be probed using different spectroscopic techniques (Raman spectroscopy, x-ray spectroscopies, sum-frequency generation (SFG)) as the reaction proceeds down the reaction pathways. The reaction products and their kinetic energy distributions can be probed using time-of-flight mass spectrometry. Piecing together these snapshots, we can obtain an understanding of the step-by-step processes that occur on the surface of catalysts.

 

Pump-Probe