N-rich covalent organic polymer in situ modified TiO₂ for highly efficient photocatalytic hydrogen evolution

TiO₂ has been everlastingly employed as popular photocatalyst for water splitting. However, the wide band gap (3.0-3.2 eV) and poor absorption to visible light of TiO₂ result in a low utilization of solar energy and limit its large-scale application. To decrease its band gap and promote the utilization of full solar energy, we here modified TiO₂ by in situ growth of N-rich covalent organic polymer (termed as COP_HM). During the in situ growth of COP_HM on the surface of TiO₂, intimate contacts between TiO₂ and COP_HM were built and core-shell structures were finally formed. The derived TiO₂@COP_HM demonstrated a narrower band gap (2.53 eV) compared to raw TiO₂ (3.13 eV) and improved absorption to visible light. The optimal TiO₂@COP_HM hybrid exhibited excellent hydrogen evolution performance of 162.7 μmol h^-1 under simulated sunlight which was more than 3 times higher than raw TiO₂ (51.3 μmol h^-1). Particularly, visible light hydrogen evolution rate of TiO₂@COP_HM reached 0.65 μmol h^-1 while non-hydrogen generation was observed using raw TiO₂.