Rational design of Ru(II)-phenanthroline complex embedded porous TiO2photocatalyst for efficient hydrogen production

The design of an efficient photocatalytic system with a capability of effective photon conversion for hydrogen evolution is highly challenging. Herein, we report the first example of phenanthroline based ruthenium complexes (PRC1-3) embedded nanostructured hierarchical porous TiO2 composites (HPT) that showed impressive H-2 evolution reaction (HER) under simulated light irradiation. The introduction of the propenyl groups in the Ru-Phen complexes reveal enhanced light response (350-550 nm) with increased charge transfer behaviour and lifetime of 77-127 ns. The composite PHPT-PRC's endows high performance towards HER. The superior activity of PHPT-PRC3 exhibits H-2 yield of 3066 mu molg(cat)(-1) with a turnover number of 123 after 4 h compared to N719 sensitized PHPT (N719-PHPT). The enhancement in HER is due to the strong photon absorption in PRC3 with 3-propenyl moieties with an extended excited state lifetime. Further, the high surface area and uniform porous structures of HPT favours better transport of irradiated light absorption and enhanced charge transfer property which synergistically improves the effective charge transfer on the photocatalytic HER. The experimental observations corroborated with computational calculations which further elucidates the high efficiency of PRC3 than 1 and 2 due to favourable HOMO-LUMO energy levels, efficient charge separation and enhanced regeneration of oxidized dye. (c) 2020 Elsevier Ltd. All rights reserved.