Anchor effect in photocatalytic water splitting using boron dipyrromethene‐sensitizing dyes

Photocatalysis is an effective method for efficiently using solar energy and producing hydrogen through water splitting. In this study, we investigated an anchor group, chosen from carboxy, pyridyl, and tetrazole moieties, that easily attracts electrons from boron dipyrromethene (BODIPY) and injects them into titanium oxide (TiO₂) to synthesize a new dye‐sensitized material for photocatalytic hydrogen production. Target BODIPY sensitizers were synthesized to yield 12%–29% with BODIPY‐2‐carbaldehyde and corresponding acetonitrile derivatives treated by piperidine or triethylamine as the catalyst. The coordination of the sensitizers onto TiO₂ was examined through attenuated total reflection Fourier transform infrared spectroscopy. The energy potential of BODIPY sensitizers with respect to TiO₂ was analyzed using cyclic voltammetry and differential voltammetry. The molecular orbitals of the BODIPY sensitizers were analyzed using density functional theory. Visible‐light‐driven photocatalysis with ascorbic acid as the sacrificial electron donor demonstrated hydrogen production. The photocurrent test showed that photo‐induced electrons were injected into TiO₂ under visible light irradiation which supported dye‐sensitized photocatalytic hydrogen production. The absorption spectra after the photocatalytic reaction showed no change in the pyridyl anchor group system, which suggested that the pyridyl‐anchored dye‐sensitized photocatalyst showed a good hydrogen production rate and stability.