CO2 capture, storage, and conversion using a praseodymium-modified Ga2O3 photocatalyst

Abstract

Praseodymium-modified gallium oxide (Pr/Ga₂O₃) was found to show enhanced activity and selectivity toward CO evolution in the photocatalytic conversion of CO₂ using H₂O as an electron donor in an aqueous solution of NaHCO₃ as compared to those of bare Ga₂O₃. The as-prepared Pr species, including Pr(OH)₃ and Pr₂O₂CO₃, on the surface of Ga₂O₃ were transformed into Pr hydroxycarbonates (Pr₂(OH)_2(3−x)(CO₃)_x) and Pr carbonate hydrates (Pr₂(CO₃)₃·8H₂O) in an aqueous solution of NaHCO₃, and then the Pr₂(OH)_2(3−x)(CO₃)_x was further transformed into Pr₂(CO₃)₃·8H₂O by CO₂ bubbling under photoirradiation. This indicates that CO₂ molecules dissolved in water can be captured and stored using Pr species in an aqueous solution of NaHCO₃ under CO₂ bubbling. More importantly, Pr₂(OH)_2(3−x)(CO₃)_x and Pr₂(CO₃)₃·8H₂O accumulated on the surface were decomposed to CO over the Ga₂O₃ photocatalyst with a Ag cocatalyst. Consequently, Ag/Pr/Ga₂O₃ exhibits much higher activity (249 μmol h⁻¹ of CO) than the pristine Ag-loaded Ga₂O₃ (136 μmol h⁻¹ of CO).