Barium- and Phosphorus-Codoped g-C<sub>3</sub>N<sub>4</sub> Microtubes with Efficient Photocatalytic H<sub>2</sub> Evolution under Visible Light Irradiation
Dan Long, Wenlan Chen, Shaohui Zheng, Xi Rao, Yongping Zhang
Abstract
Graphitic carbon nitride (CN) is a fascinating metal-free photocatalyst used to generate hydrogen utilizing solar energy directly, and its performance can be improved by tuning the electronic structure, enhancing the visible light absorbance via element doping, and increasing the surface active sites via nanostructure formation. Herein, porous Ba–P-codoped g-C3N4 microtubes (Ba–P–CN) with a large specific surface area are synthesized by calcined melamine, barium chloride, and hypophoaphoeous acid via a hydrothermal method. Ba–P-codoped g-C3N4 microtubes increase the specific surface area and visible light harvesting and narrow the band gap. Ba–P–CN exhibits enhanced photocatalytic performance, reaching H2 evolution rate up to 12.3 μmol/h under light λ > 420 nm, which is 13.2 times as high as that of CN. Experimental verification and theoretical calculation indicate that Ba and P doping increases the delocalized density of states distribution of highest occupied molecular orbitals and lowest unoccupied molecular orbitals and narrowed the band gap, and the formation of microtube structures augments the large specific surface area, in addition to improving the photocatalytic performance of g-C3N4.