Design and synthesis of porous ZnTiO₃/TiO₂ nanocages with heterojunctions for enhanced photocatalytic H₂ production

Despite the tremendous potential applications of hollow micro/nanostructures, their composition has been limited to mainly single chemical compounds. Inspired by recent innovations in the areas of metal organic frameworks (MOFs) and nanocoating, here, we report the rational synthesis of mesoporous ZnTiO₃/TiO₂ hollow polyhedra (MZTHP) obtained by hydrothermal treatment of zeolitic imidazolate framework-8 (ZIF-8)@TiO₂ core-shell polyhedral particles. The subsequent calcination of these particles caused phase transformation from TiO₂ to ZnTiO₃ and eventually induced the formation of Zn₂TiO₄. In addition, the fabrication of these hollow structures revealed a way for the preparation of hollow polyhedral photocatalysts with Pt nanoparticles deposited onto their external surface (PHS-1) or encapsulated inside their hollow structures (PHS-2). Importantly, these two types of Pt-decorated nanoparticles are shown to exhibit an improved yet distinctly different performance for photocatalytic hydrogen production, highlighting that the photocatalytic activity correlates with the Pt location and dispersion.