Doctor of Philosophy (PhD)
The electrochemical reduction of CO2 has been proposed as a method of storing electrical energy from renewable sources in the form of hydrocarbon fuels. By reverting CO2 into high energy density fuels, a CO2-neutral fuel cycle becomes possible while still hydrocarbon fueled engines. Cu and Au metals have been found to be particularly effective at catalyzing this reaction, yielding a majority of hydrocarbons and CO respectively. However, the CO2 electroreduction reaction is still poorly understood and catalysts that possess both high energy efficiency and high yield are not yet developed. Nanoscale catalysts offer the ability to both increase yield and alter the selectivity of the CO2 reduction reaction.
This dissertation investigates the use of transition metal nanoparticles as electrocatalysts and how they can be used to control the selectivity and yields of the CO2 reduction reaction. Cu nanoparticles on ZnO, Au nanoparticles, CuAu alloy nanoparticles, Ag nanoparticles on Fe and Ni nanoparticles on Ag were all fabricated and evaluated as CO2 reduction catalysts. The CuZnO catalysts were shown to improve selectivity to alcohols by an order of magnitude compared to Cu foils. The Au nanoparticles were supported on carbon black using polymer binders, showing that nanoparticles immobilized in a binder containing a sulfonate group has higher CO selectivity and improved onset potentials. CuAu alloys were evaluated at 2 nm and 6 nm nanoparticle sizes and as a bulk foil. The 6 nm nanoparticles were found to yield two orders of magnitude more CO than the foils and the 2 nm nanoparticles were found to yield 3x more CO, indicating strong size effects and the existence of an optimal particle size. NiAg and FeAg catalysts were fabricated via electrodeposition as in investigation into the effects of bimetallic active sites. The Ni and Fe were found to act as catalytic poisons in most situations, but the FeAg was found to produce methane, a product not seen on either pure Fe or Ag.
Andrews, Evan Michael, "Electrochemical Reduction of CO2 Using Metal Nanoparticles" (2017). LSU Doctoral Dissertations. 4109.