Hydrogarnet-derived Rh/TiO2 catalysts with a low rhodium content for a photocatalytic hydrogen production

[Display omitted] •Hydrogarnet-type salt Ca3[Rh(OH)6]2 was used for Rh/TiO2 preparation for first time.•Hydrogen evolution from ethanol solutions was successfully performed (λ = 380 nm)•In situ reduction of Ca3[Rh(OH)6]2/TiO2 to Rh/TiO2 during H2 evolution was observed.•The highest activity 3.3 mmol·h−1·g−1 with AQE = 1.8% was achieved for 0.1% Rh/TiO2.•Unprecedent activity per gram of rhodium (21 mol·h−1) was registered for 0.01% Rh/TiO2. A novel protocol for the preparation of Rh-decorated TiO2 photocatalysts with the rhodium content of 0.01–1.0 wt% has been developed based on the deposition of the low-soluble hydrogarnet type salt Ca3[Rh(OH)6]2. Under 380-nm irradiation in water–ethanol mixtures the photoinduced reduction of Ca3[Rh(OH)6]2/TiO2 results in the formation of highly active Rh/TiO2 photocatalysts with nanoparticulated rhodium co-catalyst preferably attached to the surface of anatase particles. The catalysts generate up to 21 mol of H2 per gram of rhodium per hour via a photocatalytic hydrogen evolution reaction (HER) outperforming the activity of the analogous materials reported to date.