Efficient photocatalytic oxygen production over Ca-modified LaTiO2N

Abstract

LaTiO2N has been considered a promising candidate for efficient photocatalytic water splitting. However, its photocatalytic activity is often hampered by the presence of structural defects and poor charge mobility. In this work, we introduced Ca into the crystal structure of LaTiO2N via a simple co-precipitation method and investigated the photocatalytic and photoelectrochemical properties for the full range solid solution La1−xCaxTiO2+yN1−y (0⩽x, y⩽1). Our results show that incorporating Ca into LaTiO2N induces a strong structural shrinkage as well as a space group change from I mma to P nma around a middle doping point (x=0.5). The presence of Ca effectively boosts the photocatalytic oxygen production and aids photocurrent extraction for LaTiO2N. The best photocatalytic activity was achieved for sample La0.3Ca0.7TiO2.7N0.3 with oxygen production rate ∼66.96μmol/h under visible light illumination (λ⩾420nm), corresponding to apparent quantum efficiency ∼3.13%. XPS analysis revealed a substantial reduction in surface Ti3+ species and a removal of A-site cation segregation for samples containing Ca. Further photoelectrochemical analysis highlights the critical role of Ca in enhancing the charge mobility of LaTiO2N. The better photocatalytic performance of Ca-modified LaTiO2N can be understood as a result of defect removal, high charge mobility, and improved surface charge migration pathways that considerably prolong the lifetimes of photogenerated charges.