Al‐Doped LaTiO₂N Prepared via Flame Spray Pyrolysis for Photocatalytic Hydrogen Evolution

LaTiO 2 N photocatalysts are attractive because they are responsive to visible light up to a wavelength of 600 nm. However, during the nitridation process to produce LaTiO 2 N from La 2 Ti 2 O 7 , the introduction of defects can cause a reduction in the hydrogen evolution activity of the photocatalyst, which limits its application to overall water splitting. Such defects can arise due to the change in crystal structure and the occurrence of overnitridation. Herein, it is demonstrated that nitridation of a metastable La–Ti oxide obtained by flame spray pyrolysis (FSP) can suppress the formation of such defects. A detailed analysis of the transition pathway during nitridation reveals that a combination of FSP and Al doping is essential for suppressing mesopore formation resulting from the volume change and Ti 4+ reduction due to overnitridation. This leads to an increase in the apparent quantum yield for Al‐doped LaTiO 2 N during the visible‐light‐driven hydrogen evolution reaction, compared to that for undoped LaTiO 2 N. In the present study, insights are provided into the importance of minimizing structural changes during the synthesis of oxynitride photocatalysts by designing isostructural precursors for enhanced photocatalytic activity.