Homogeneous distribution of highly dispersed Pt species over O and P co-doped g-C3N4 and its superior photocatalytic H2 evolution activity

Abstract

In this study, we synthesized O and P co-doped graphitic C3N4 (OPCN) materials by a one-step calcination method and prepared Pt/OPCN photocatalysts for the photocatalytic H2 evolution reaction. Among the Pt/OPCN catalysts with various O and P contents, Pt/OPCN2 exhibited the highest H2 evolution rate of 2198 μmol·g−1 (AQE = 7.33%), which was 1.65 times higher than that of Pt/CN (1330 μmol·g−1). Moreover, Pt/OPCN2 demonstrated excellent photocatalytic properties, such as suitable band gap (2.50eV) for visible light and efficient charge separation of photoexcited electron–hole pairs, which was confirmed by ultraviolet-visible spectroscopy, electrochemical impedance spectroscopy, photoluminescence spectroscopy, and time-resolved photoluminescence measurements. Fundamentally, the Pt species effectively interacted with neighboring P=O and C=O functional groups that optimally located defective OPCN2, resulting in a homogeneous formation of highly dispersed PtO evenly distributed over Pt/OPCN2, as confirmed by X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, and density functional theory calculations. However, excessive O and P contents of OPCN3 damaged the morphological structure of g-C3N4, inducing a poor interaction between the Pt species and OPCN3 and forming isolated Pt nanoparticles, resulting in the low photocatalytic activity of Pt/OPCN3.