Dominant {100} facet selectivity for enhanced photocatalytic activity of NaNbO3 in NaNbO3/CdS core/shell heterostructures

Design and engineering of crystalline advanced photocatalysts with specific facets is one of the most challenging tasks to enhance the photocatalytic performance. The surface energy of different facets is different in a crystal which leads to a corresponding change in their photocatalytic behaviour. The present study provides an experimental as well as theoretical understanding of the role of different facets of NaNbO3 in cubic and orthorhombic phases with crystals showing cubic and cuboctahedron morphologies in enhancing the photocatalytic activity of NaNbO3/CdS core/shell heterostructures. Herein, we discuss the importance of the approach of facet-selective synthesis and trace the origin of enhanced photoelectrochemical (PEC) water splitting and photocatalytic dye degradation activity for calculated surface energies of the {100} family of facets of the cubic phase and the (110) and (114) facets of the orthorhombic phase of NaNbO3. We propose that different mechanisms contribute to the enhancement of catalytic activity in these two phases. In the prepared core/shell heterostructures containing NaNbO3 as the core material, the presence of highly reactive facets of the cubic phase contributes to higher photocatalytic activity as compared to the orthorhombic phase which has a spatial charge separation assisted inter-facet charge transfer mechanism.