FIRST-PRINCIPLES SIMULATIONS FOR CATALYSIS FOR SUSTAINABLE PRODUCTION OF FUELS AND CHEMICALS

Abstract

The development of renewable energy conversion and storage systems has recently attracted significant interest. One such system is the direct use of renewable energies for the selective synthesis of high-value chemicals through the CO2 photo/electroreduction reaction, water splitting for hydrogen fuel production, and production of essential chemicals such as hydrogen peroxide. The general purpose of this work is to use different computational methods in the framework of density functional theory to perform an in-depth study of the selectivity, activity, and stability of electrocatalysts in energy conversion reactions and storage. The present work incorporates three different catalytic systems projects. The first project focused on the CO2 photocatalytic activity of two different perovskite systems of various structures and chemical compositions, CsPbBr3 and Cs3Sb2Br9. Compared to the poor catalytic activity of CsPbBr3, Cs3Sb2Br9 showed superior photocatalytic activity. The enhanced photoactivity of Cs3Sb2Br9 was attributed to the ability of the Sb-Br bond to elongate for the temporary accessibility of Sb adsorption sites. The second project focused on H2O2 production through the oxygen reduction reaction on Pt and PtP2 electrocatalysts. The simulations revealed that compared to Pt, which reduces O2 to H2O at high overpotential, PtP2 selectively produces H2O2 at thermodynamic potential with minimal overpotential. The selectivity and high activity of PtP2 stem from geometric and electronic effects and the role of P atoms in enhancing the activity of PtP2 is established. The third project focused on the electroreduction of CO2 to 1-butanol on phosphorus-rich CuP2 catalysts. Prior experiments showed the production of butanol from the electroreduction of CO2 on CuP2 electrocatalysts without the production of CO. Simulations, based on grand canonical density functional theory, revealed a plausible mechanism based on the coupling of formaldehyde and then acetaldehyde toward the formation of 1-butanol. Simulations revealed the critical role of P-atoms in CO2 reduction through the hydride transfer mechanism from adsorbed hydride on P-sites. Finally, studies on CuP2 systems revealed the importance of going beyond conventional density functional theory in studying CO2 electroreduction to include solvation and electric potential effects.