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

•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.