(345g) Insights Into the Performance of Cu2O in Photocatalytic CO2 Conversion
AIChE Annual Meeting
2013 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Applications of DFT+X in Catalysis II
Tuesday, November 5, 2013 - 5:00pm to 5:15pm
Photocatalytic conversion of CO2 to methanol requires new, efficient, and low-cost catalytic materials for this process to be a cost-effective source of fuel. Cu2O is one attractive semiconductor with many optimal properties for this application. The limitations of Cu2O as a photocatalytic material can be better understood through theoretical studies of its physical, electrical, chemical, and optical properties. By identifying the source of the limitations, the possibility of rational design is created, allowing for the study of how modifications to its composition may improve its performance.
We use density functional theory (DFT) +U and hybrid-DFT to evaluate many of the properties of Cu2O that are essential factors in its functionality as a photocatalyst. The need for DFT+U and hybrid-DFT is first established by a comparison to conventional DFT in the prediction of Cu2O bulk properties. We then use a hybrid-DFT/G0W0 approach to evaluate the Cu2O band gap and band edge potentials, which define the material’s sunlight absorption efficiency and its thermodynamic ability to catalyze redox reactions. A combination of DFT+U and HSE is used to examine the energetics and electronic structure of trap states and delocalized hole states created by intrinsic bulk cation vacancies. Trap states are detrimental to photoconductivity by promoting carrier recombination, and inhibiting trap states will help to optimize of Cu2O as a photocatalyst. Based on our observations, we suggest doping with Li as a method to prevent deleterious trap state formation. Finally, we use DFT+U to analyze reactant adsorption on the Cu2O(111) surface, and show the importance of the coordinatively unsaturated surface copper atom as the adsorption site.