Assembly of a novel Fe2TiO5-impregnated donor-π-acceptor conjugated carbon nitride for highly efficient solar water splitting

Carbon nitride (CN) exhibits low photocatalytic performance for the energy conversion during photocatalytic water splitting (PWS) under visible light spectrum. Designing novel high-performance CN-based photocatalysts via providing advanced intrinsic characteristics to pristine CN material may further endorse the PWS process. Integrating organic molecules within the skeleton of CN is an interesting strategy to lessen the extent of charge recombination by promoting effective charge separation and transportation, thereby boosting light absorption and photocatalytic performances. Yet, limited progresses have been made along this line. We have carefully chosen and fused previously unexplored organic donor-π-acceptor-type 2,6-diaminopurine (DP) molecules within the skeleton of CN via a superficial organic molecular engineering. Moreover, the subsequent introduction of Fe2TiO5 with copolymerized CN-DP10.0 and pristine CN provide considerably more surface-active sites to form heterojunction material, synergistically extending both the optical absorption range and the lifetime of photoinduced electron. More importantly, with a typical type-II heterojunction formation, the CN and Fe2TiO5 energy levels are overlapped and compatible, thereby significantly accelerating both electron and hole transfer processes. These beneficial characteristics in turn lead to an outstanding apparent quantum yield (AQY) of 61.7% at a wavelength of 420 nm, together with highly efficient and greatly improved photocatalytic hydrogen (H2) (165.7 μmol/h) along with oxygen (O2) (6.2 μmol/h) evolution reactions in visible spectrum at 420 nm. These values are 15.7 and 11.4 times more than those of the pristine CN (9.9 μmol/h and 0.5 μmol/h). Consistent with these experimental findings, our computational simulations show that integration of Fe2TiO5 and DP molecules within the CN framework decreases the band gap from 3.25 to 2.55 eV, suggesting remarkable photocatalytic activities of Fe2TiO5/CN-DP10.0. As a result, it is anticipated that this work will offer a significant avenue for scientific investigation into the next generation of renewable energy employing improved heterostructure photocatalyst predicated on organic ligands.