Acid-inducing {110}/{121} facet junction formation boosting the selectivity and activity of CO2 photoreduction by BaTiO3 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 BaTiO3 is random and the study of photocatalytic CO2 reduction is in its infancy. Herein, we develop an unprecedented polyhedral BaTiO3 nanoparticle with oriented growth of {110} facets via a hydrothermal and acid-etching process. Compared to the original octahedral BaTiO3, polyhedral BaTiO3 nanoparticles with {110}/{121} facet junctions have significantly enhanced photocatalytic activity for the evolution of CO and CH4. BaTiO3 nanoparticles with {110}/{121} binary facet junctions exhibit a photocatalytic activity with maximal CO and CH4 yields of 3.77 μmol g−1 and 3.61 μmol g−1, respectively, while the original octahedral BaTiO3 only shows CO and CH4 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 BaTiO3 nanoparticle with a {110}/{121} binary facet junction provides a cascade path for efficient charge flow compared to octahedral BaTiO3 with {121} facets. Molecular dynamics calculation explores the path of CO2 reduction reaction. This work gives an in-depth insight into a crystal facet junction with a cascade path and its selective CO2 reduction reactions for efficient photocatalysts.