For photocatalysts the band gap energy and electronic band structure is of tremendous importance. To efficiently utilize solar light the band gap energy should be smaller than 3 eV. The minimum band gap of photocatalysts should be larger than 2 eV for efficient use in water cleavage. [I. Dincer; C. Zamfirescu; Sustainable Hydrogen Production; ScienceDirect, 2016, 309-391] Ce₂Zr₃(MoO₄)₉ has a band gap of about 3 eV and is a rather interesting material for the use as a photocatalyst. To achieve a slightly smaller band gap TiO₂ doped Ce₂Zr₃(MoO₄)₉ was synthesized as the band gap of TiO₂ is smaller than ZrO₂. Due to the positive effects of Eu³⁺ doped La₂Zr₃(MoO₄)₉, Eu³⁺ doped Ce₂Zr₃(MoO₄)₉ was additionally prepared.