Facile preparation and enhanced photocatalytic H2-production activity of Cu(OH)2 cluster modified TiO2

Abstract

Cu(OH)₂ cluster-modified TiO₂ (Cu(OH)₂/TiO₂) photocatalysts were prepared by a simple precipitation method using Degussa P25 TiO₂ powder (P25) as a support and copper nitrate as a precursor. Low-power ultraviolet light emitting diodes (UV-LEDs) were used as the light source for a photocatalytic water splitting reaction. The prepared samples show especially high photocatalytic H₂-production activity from aqueous solutions containing ethylene glycol as sacrificial reagent even without a Pt co-catalyst. The optimal Cu(OH)₂ loading content was found to be 0.29 mol%, giving an H₂-production rate of 3418 μmol h⁻¹ g⁻¹ with a quantum efficiency (QE) of 13.9%, which exceeded the rate on pure TiO₂ by more than 205 times. This high photocatalytic H₂-production activity is attributed to the presence of Cu(OH)₂ clusters on the surface of the TiO₂. The potential of Cu(OH)₂/Cu (Cu(OH)₂ + 2e⁻ = Cu + 2OH⁻, E^o = −0.224 V) is slightly lower than conduction band (−0.26 V) of anatase TiO₂, whilst being higher than the reduction potential of H⁺ (2H⁺ + 2e⁻ = H₂, E^o = −0.000 V), which favors the electron transfer from the CB of TiO₂ to Cu(OH)₂, and the reduction of H⁺, thus enhancing photocatalytic H₂-production activity. This work not only shows a possibility for the utilization of low cost Cu(OH)₂ clusters as a substitute for noble metals (such as Pt) in photocatalytic H₂-production, but also for the first time exhibits a facile method for enhancing H₂-production activity by using hydroxide as a co-catalyst .