Acid-inducing {110}/{121} facet junction formation boosting the selectivity and activity of CO photoreduction by BaTiO nanoparticles

The exposure of anisotropic crystal facets of photocatalysts is an effective method to address the issue of the directional transfer of photoexcited carriers. However, the facet effect of BaTiO 3 is random and the study of photocatalytic CO 2 reduction is in its infancy. Herein, we develop an unprecedented polyhedral BaTiO 3 nanoparticle with oriented growth of {110} facets via a hydrothermal and acid-etching process. Compared to the original octahedral BaTiO 3 , polyhedral BaTiO 3 nanoparticles with {110}/{121} facet junctions have significantly enhanced photocatalytic activity for the evolution of CO and CH 4 . BaTiO 3 nanoparticles with {110}/{121} binary facet junctions exhibit a photocatalytic activity with maximal CO and CH 4 yields of 3.77 μmol g −1 and 3.61 μmol g −1 , respectively, while the original octahedral BaTiO 3 only shows CO and CH 4 evolution of 1.80 μmol g −1 and 2.09 μmol g −1 . Density functional theory calculations and photo-deposition results reveal that the band energy of a BaTiO 3 nanoparticle with a {110}/{121} binary facet junction provides a cascade path for efficient charge flow compared to octahedral BaTiO 3 with {121} facets. Molecular dynamics calculation explores the path of CO 2 reduction reaction. This work gives an in-depth insight into a crystal facet junction with a cascade path and its selective CO 2 reduction reactions for efficient photocatalysts. With the introduction of {110} facets and an increasing exposure ratio, the photoreduction CO 2 reaction of acid-etched BaTiO 3 occurs on different facets of BaTiO 3 , and the corresponding reactants/products and photocatalytic mechanism are presented.