Eu(III)–BaTiO3 nanoparticles and BaTiO3/TiO2/Ti sheets; photocatalytic and electrocatalytic CO2 reduction

Perovskite barium titanate (BaTiO3, BTO) has shown a high potential as catalysts. Eu(III) ion has been employed as a unique red-luminescence activator in a host metal oxide. Herein, Eu(III)-doped BTO nanoparticles (NPs) were synthesized, and their photocatalytic CO2 reduction activities and products were examined. Major CO2 reduction products were observed to be CH3OH, CO, and CH4. Doped Eu(III) ions were used as a tracer to discuss the roles of dopants by measuring photoluminescence (PL) properties and PL lifetimes. Electrocatalytic CO2 reduction performances were evaluated using BTO electrodes directly grown on a TiO2/Ti sheet, and Cu-deposited BTO electrodes. H2 was a major product and formate was significantly increased upon Cu deposition on the surface. Surface oxidation states of BTO with dopant concentration and overlayer Cu metal were fully discussed by X-ray photoelectron spectroscopy. The surface electronic structure was altered by doping and metal deposition, and thereby the selectivity and productivity for CO2 reduction were varied. The unique physicochemical properties and CO2 reduction demonstration tests provide significant information on understanding CO2 reduction mechanism and the development of BTO-based catalysts for energy and environment.