Impact of Glycerol as Scavenger for Solar Hydrogen Production from Water

The photocatalytic activity of titania supported bimetallic Cu-Ni photocatalysts was assessed and optimized for hydrogen production from water under visible light illumination (12.2 klux intensity). Research parameters investigated include total metal loading and Cu:Ni mass composition of the photocatalysts. The best performing photocatalyst was 10 wt% Cu-Ni/TiO2 with Cu:Ni mass composition of 9:1, producing 6.1 mL of hydrogen over 2 hr reaction time. The impact of glycerol addition as hole-scavenger on the efficiency of solar hydrogen production from water was also investigated. Addition of 2.0 mL of glycerol to 8.0 mL of water enhanced the solar hydrogen production from 6.1 mL to 9.5 mL. If metal was not incorporated onto TiO2, the hydrogen production was minimal, 2.0 mL after 2 hr reaction. The absorption spectra of metal-incorporated photocatalysts were not only enhanced in the UV region, they were also shifted to the visible region. All band gaps of the metal-incorporated photocatalysts were reduced compared to P25 TiO2 (3.16 eV). The lowest band gap of 2.78 eV was displayed by 10 wt% Cu-Ni/TiO2 bimetallic photocatalyst. Photooxidation of glycerol produced glyceraldehyde, glycolic acid and oxalic acid as intermediates.