Zr-Doped Mesoporous Ta3N5 Microspheres for Efficient Photocatalytic Water Oxidation

Tantalum nitride (Ta3N5) has been considered as a promising candidate for photocatalytic water splitting because of its strong visible-light absorbance as far as 600 nm. However, its catalytic activity is often hampered by various intrinsic/extrinsic defects. Here, we prepared a series of Zr-doped mesoporous tantalum nitride (Ta3N5) via a template free method and carried out a detailed investigation of the role of Zr doping upon the photocatalytic performance. Various physicochemical properties including crystal structure, optical absorption, and so on were systematically explored. Our results show that doping Zr into Ta3N5 induces an enhancement of oxygen content and a suppression of absorption band around 720 nm, indicating an increase of O-N(center dot) defects and a decrease of V-N(center dot center dot center dot) defects in the structure. Introduction of Zr significantly boosts the photocatalytic oxygen production of Ta3N5. The optimized photocatalytic oxygen production rate approaches 105 mu mol h(-1) under visible light illumination (lambda >= 420 nm), corresponding to an apparent quantum efficiency as high as 3.2%. Photoelectrochemical analysis and DFT calculation reveal that the superior photocatalytic activity of Zr-doped Ta3N5 originates from a high level of O-N(center dot) defects' concentration, which contributes to a high electron mobility, and a low level of V-N(center dot center dot center dot) defects' concentration, which often act as charge recombination centers.