(685a) Photochemical Reduction of CO2 Using Delafossite Oxides

The photochemical reduction of CO₂ in the
presence of H₂O to form CO, CH₄ and other light gases
with industrial value is an interesting approach for dealing with CO₂
emissions. This approach can generate tangible revenue to help offset carbon
capture and storage costs by generating a product stream with industrial demand
from a CO₂ feedstock. Delafossite
materials of the general stoichiometry ABO₂
are a new class of photocatalysts being considered
for this application. Recent theoretical calculations have indicated that
B-site alloying in these systems breaks the inversion symmetry of the crystal
giving rise to symmetry forbidden optical transitions across the band structure
of the material. B-site alloying can also be used to modulate the delafossite band structure to create new, low energy band
gaps, as well as to align band edge positions for the photochemical redox reactions needed specifically for CO₂
applications. The photochemical activity of CuAlO₂, CuAl_0.9Fe_0.1O₂,
CuGaO₂ and CuGa_1-xFe_xO₂ (x=0.05,
0.1, 0.15, 0.2) for the reduction of CO₂ will be presented. The photoreduction of CO₂ in the presence of H₂O
vapor using CuAlO₂, CuAl_0.9Fe_0.1O₂,
CuGaO₂ and CuGa_1-xFe_xO₂ produces CO
with little evidence for other products such as H₂ or
hydrocarbons.  The observed optical
spectra will be compared to the theoretical band structure in these systems to
better understand how B-site alloying can be used to control the optical
activity of this material for photochemical applications.  Additionally, the calculated band edge
positions will be compared to CO₂ reduction and H₂O
oxidation potentials to better understand the reaction products and yields
observed experimentally.