Overall water splitting over Pt/TiO₂ catalyst with Ce³⁺/Ce⁴⁺ shuttle charge transfer system

The experiments on photocatalytic hydrogen production from aqueous solution of Ce₂(SO₄)₃ and photocatalytic oxygen production from aqueous solution of Ce(SO₄)₂ were carried out on the same catalyst platinized Degussa P25. Pure oxygen was shown to evolve from Ce(SO₄)₂ solution and pure hydrogen from Ce₂(SO₄)₃ solution with stoichiometric formation of Ce₂(SO₄)₃ and Ce(SO₄)₂, respectively. The rate of photocatalytic hydrogen production was lower than the rate of photocatalytic oxygen production on the same catalyst. The influence of initial cerium salt concentration, acidity and catalyst loading was checked for photocatalytic oxygen and hydrogen production. The dependences of the hydrogen and oxygen production rate on Ce³⁺ and Ce⁴⁺ concentration have maxima. Kinetic equation for the rate of photocatalytic oxygen production was proposed that takes into account the inner filter effect; constants of this equation were calculated. Optimal conditions for photocatalytic reactions were found and explained. The shuttle charge transfer regime was tested for consecutive O₂ and H₂ production over the same and different portions of catalyst and same Ce³⁺/Ce⁴⁺ system. It was found that separate catalyst batches are needed to avoid mixed evolution of hydrogen and oxygen.