Advancing bandgap tuning: Novel nitrogen doping in KLaTiO₄ with uncompromised crystallinity

KLaTiO₄ is a promising photocatalyst, producing 9.54(11) µmol of hydrogen gas per hour. Its high bandgap, of 4.09 eV, makes it unsuitable for direct photocatalysis under sunlight irradiation. In this study two novel methods of doping KLaTiO₄ with nitrogen were studied, in an attempt to reduce the bandgap of KLaTiO₄ without inducing structural degradation of the photocatalyst, which adversely affects the hydrogen evolution rate. The first method involves post-synthesis calcination of KLaTiO₄ with urea under a nitrogen atmosphere, and the second method attempts to introduce nitrogen during synthesis, by replacing TiO₂ with TiN as a starting reagent. The samples were structurally characterised using powder X-ray diffraction and their bandgap and photocatalytic performance determined by Tauc plot and hydrogen evolution testing. Density Function Theory calculations have been used to probe the likely site of nitrogen doping.