Hierarchical\nHoneycomb Br-, N‑Codoped TiO₂ with Enhanced Visible-Light\nPhotocatalytic H₂ Production

Abstract

The halogen elements modification\nstrategy of TiO₂ encounters\na bottleneck in visible-light H₂ production. Herein, we\nhave for the first time reported a hierarchical honeycomb Br-, N-codoped\nanatase TiO₂ catalyst (HM-Br,N/TiO₂) with enhanced\nvisible-light photocatalytic H₂ production. During the\nsynthesizing process, large amounts of meso–macroporous channels\nand TiO₂ nanosheets were fabricated in massive TiO₂ automatically, constructing the hierarchical honeycomb structure\nwith large specific surface area (464 m² g^–1). cetyl trimethylammonium bromide and melamine played a key role\nin constructing the meso–macroporous channels. Additionally,\nHM-Br,N/TiO₂ showed a high visible-light H₂ production\nrate of 2247 μmol h^–1 g^–1, which is far more higher than single Br- or N-doped TiO₂ (0 or 63 μmol h^–1 g^–1,\nrespectively), thereby demonstrating the excellent synergistic effects\nof Br and N elements in H₂ evolution. In HM-Br,N/TiO₂ catalytic system, the codoped Br–N atoms could reduce\nthe band gap of TiO₂ to 2.88 eV and the holes on acceptor\nlevels (N acceptor) can passivate the electrons on donor levels (Br\ndonor), thereby preventing charge carriers recombination significantly.\nFurthermore, the proposed HM-Br,N/TiO₂ fabrication strategy\nhad a wide range of choices for N source (e.g., melamine, urea, and\ndicyandiamide) and it can be applied to other TiO₂ materials\n(e.g., P25) as well, thereby implying its great potential application\nin visible-light H₂ production. Finally, on the basis of\nexperimental results, a possible photocatalytic H₂ production\nmechanism for HM-Br,N/TiO₂ was proposed.