Nitrogen-doped LaZrTa3O11 as a visible light-active photocatalyst for water-reduction and -oxidation reactions

Abstract

Nitrogen doping was applied to layered compound LaZrTa₃O₁₁ (a wide bandgap semiconductor photocatalyst). Bandgap reductions >2.2 eV were achieved by this modification, which effectively red-shifted the light-absorption edge of LaZrTa₃O₁₁ from 300 nm to ∼650 nm. Nitrogen-doped LaZrTa₃O₁₁ (i.e., LaZrTa₃O_11−xN_y) was now active for both water-reduction and -oxidation reactions under visible-light illumination (λ ≥400 nm) with good durability and stability. An apparent quantum efficiency (AQE) as high as 0.53% at 420 ± 20 nm was achieved for water-oxidation reactions. Further analyses suggested that its visible-light activity originated mainly from an uplift of the valence band edge as a result of nitrogen incorporation. This strategy to achieve visible-light activity was very inspiring and could be applicable to other layered compounds that are active only under ultraviolet-light illumination.