Tetragonal-zircon BiVO4: a better polymorph for the formation of coherent type-II heterostructures for water splitting applications

Abstract

The monoclinic-scheelite (m-s) polymorph of BiVO₄ has the highest photocatalytic activity, whereas tetragonal-zircon (t-z) has the lowest photocatalytic activity, which may be due to a higher band gap. However, t-z has the highest crystal symmetry, which makes it a more suitable candidate to form coherent type-II interfaces for the efficient separation of electron–hole pairs. Furthermore, the method of preparation (e.g. low temperature and moderate pH) of t-z is more facile compared to the m-s polymorph. Hence, in this report, we construct coherent isomaterial and heteromaterial type-II heterostructures by facet engineering of low index surfaces of t-z polymorph with different semiconductor materials (e.g. ZnO, TiO₂, CdSe, and ZnS) by screening the band gap, band edge positions, and lattice misfit strain. On the basis of the calculated band-edge positions, the polymorphs of BiVO₄ can form 212 combinations of the type-II interface, which reduces to 17 coherent interfaces with lattice misfit strain between 1.55% to 28.5% when translational symmetry, atomic positions, lattice mismatch, and bond complementarity have been imposed. Furthermore, the current study suggests that t-z polymorphs can form more coherent interfaces (4 out of 168), which may be due to its highest symmetry structure in comparison to previously formed 67 isomaterial and heteromaterial type-II heterostructure combinations of BiVO₄ (1 out of 67), which suggests that t-z can be a suitable candidate for the formation of type-II coherent interfaces for PEC/PC applications.