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 COPHM). During the in situ growth of COPHM on the surface of TiO2, intimate contacts between TiO2 and COPHM were built and core-shell structures were finally formed. The derived TiO2@COPHM demonstrated a narrower band gap (2.53 eV) compared to raw TiO2 (3.13 eV) and improved absorption to visible light. The optimal TiO2@COPHM 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@COPHM reached 0.65 μmol h−1 while non-hydrogen generation was observed using raw TiO2.