Book Description
This study reports the role of electrostatics in photocatalysis for optimizing hydrogen evolution from water. Ruthenium deposited/rhodium doped strontium titanate (Ru/Rh(3%):SrTiO3) nanoparticles have been synthesized to demonstrate hydrogen evolution capability. This nanostructured system develops visible light absorptivity after doping with 3% rhodium that further improves after the photodeposition of ruthenium metal particles. The Rh(3%):SrTiO3 nanoparticles obtain an average hydrogen evolution rate of 20 [mu]mol H2 h−1 compared to 42 [mu]mol H2 h−1 after the addition of 1M Na2HPO4 electrolyte. Furthermore, Ru/Rh(3%):SrTiO3 yield an average hydrogen production rate of 22 [mu]mol H2 h−1 without electrolytes and 32 [mu]mol H2 h−1 after the addition of 1M Na2HPO4. All systems are irradiated with visible light and include 0.05M K4Fe(CN)6 as the sacrificial electron donor. Lower production rates for Ru/Rh(3%):SrTiO3 than Rh(3%):SrTiO3 are observed due to particle agglomeration and competing reaction for the reduction of water and oxidized sacrificial electron donor. Surface photovoltage spectroscopy (SPS) measurements confirm n-type semiconducting material. Quenching photovoltages up to 1450 mV for Rh(3%):SrTiO3 and 280 mV for Ru/Rh(3%):SrTiO3 are observed because of ionic screening from adding 0.05M Na2HPO4. Experimental results are evaluated using Coulomb’s Law for electrostatic potential and charge density of a capacitor to analyze photochemical charge separation efficiency.