Photocatalytic production of hydrogen from aqueous solution containing CN− as a hole scavenger Original Research Article

The effect of CN− as a hole scavenger on the photocatalytic hydrogen evolution from water was investigated over NiO/TiO2. A considerable amount of hydrogen was produced in the presence of CN−; the total amount of hydrogen evolved was proportional to the total amount of CN− ion in the solution. Quantum yield was 0.12 at 25°C and 0.32 at 75°C; the increment of quantum yield was about 0.048 per 10°C increase of the reaction temperature. Nickel cyanide complex, Ni(CN)42−, was generated from NiO/TiO2 in the presence of CN−. The Ni complex decomposed under UV light in the course of hydrogen evolution, resulting in OCN− formation. In addition to producing valuable hydrogen, this complex decomposition under UV light might be a valuable process to treat wastewater containing harmful cyanide complexes. Heat treatment of NiO/TiO2 catalyst at 700°C was effective for reducing nickel dissolution significantly.