CAREER: Real-time control of elementary catalytic steps: Controlling total vs partial electrocatalytic oxidation of alkanes and olefins

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Hydrocarbons, molecules which consist of hydrogen and carbon atoms, are some of the most important chemicals to humanity. As supplied primarily by natural gas and oil, hydrocarbons provide most of our energy needs through combustion, and also serve as the source of many manufactured products, including plastics, lubricants, fabrics, and building materials, among others. Unfortunately, traditional high-temperature combustion and manufacturing processes are challenging to control, resulting in low energy efficiency, high emissions of carbon dioxide (CO2), and generation of undesired side products (the latter compounding process complexity and energy inefficiency through the need for downstream separations). The project explores a novel electrocatalytic approach to hydrocarbon utilization that operates near room temperature and controls the elementary steps involved in incorporating oxygen atoms into hydrocarbons such that combustion efficiency is greatly improved, while chemical manufacturing of oxygen-containing hydrocarbon products can be directed more effectively to desired products, resulting in lower energy consumption. Aside from the technical benefits, the project will be complemented by efforts to make the understanding of electrochemical processes more accessible to students and the general public. To this effect, the project includes an approach to make the behavior of electrochemical interfaces audible, thus employing these ‘electrochemical sounds’ as a tool to teach electrochemistry at the university and high school levels. The project is built on the observation that the origin of low efficiency and selectivity in hydrocarbon oxidation reactions derives from the vastly different conditions needed for each of the elementary steps involved in the catalytic reaction pathway. Controlled oxidation requires substrate adsorption in the correct binding mode, oxidation of intermediates to the desired product, and product desorption without inducing further reaction. Yet, conditions favoring one step often disfavor another. The project addresses this challenge by modulating the voltage applied to the electrocatalyst in sequence with the reaction steps, thereby rearranging the electrochemical interface formed between the electrocatalyst and the electrolyte. Independent control is thus achieved to sequentially enhance hydrocarbon adsorption, the oxidation of adsorbed compounds, and the desorption of desired products. The efficacy of the dynamic potential modulation approach will be examined in an alkane fuel cell application and in the sustainable synthesis of oxygenated precursor chemicals for plastics. Taken together, these efforts will open novel avenues to the efficient production of chemicals, while aiding the clean energy transition of the U.S. chemical industry. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.