Zr doped mesoporous LaTaON2 for efficient photocatalytic water splitting

Abstract

In spite of strong visible light absorption and ideal band edge positions, LaTaON₂ normally has very poor photocatalytic activity under ordinary conditions. Previous modifications of LaTaON₂ such as aliovalent doping generally lead to strong reduction of its visible light absorption, being unfavorable for solar energy harvesting. Here, we introduce Zr into the structure of LaTaON₂ (i.e. LaTa_1−xZr_xO_1+yN_2−y (0 ≤ x ≤ 0.15)) and successfully improve its photocatalytic activities without sacrificing its light absorption capability. More importantly, Zr doping helps to reduce Ta⁴⁺ defect concentration, improve surface hydrophilicity and induce mesoporous microstructures in LaTaON₂, all of which contribute to the superior photocatalytic activities for water splitting reactions. Apparent quantum efficiency as high as 0.93% at 420 ± 20 nm has been achieved on LaTa_0.9Zr_0.1O_1+yN_2−y (x = 0.10) for photocatalytic water oxidation reactions, being the highest AQE reported for LaTaON₂ to date. Further photoelectrochemical analysis suggests that Zr doped LaTaON₂ has better charge separation conditions, smaller interfacial charge transfer resistance and longer electron lifetime compared to pristine LaTaON₂. This simple method using Zr as a dopant can be well extended to other perovskite oxynitrides.