Pd–Ag decorated g-C3N4 as an efficient photocatalyst for hydrogen production from water under direct solar light irradiation

Abstract

A low visible light absorption efficiency and high recombination rate of photogenerated charge carriers are two major problems encountered in graphitic carbon nitride (g-C₃N₄) based photocatalysts for water splitting applications. In this work, Pd–Ag bimetallic and monometallic nanoparticles were decorated on graphitic carbon nitride by a simple chemical reduction method and evaluated for their ability to produce H₂ during water splitting reactions. The physical and photophysical characteristics of the as-prepared Pd–Ag/g-C₃N₄ photocatalysts were studied by powder X-ray diffraction (PXRD), UV-visible diffuse reflection spectroscopy (DRS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and steady state photoluminescence (PL). The Pd_0.7–Ag_0.3/g-C₃N₄ photocatalyst with an overall metal loading of 1 wt% showed a very high H₂ generation rate of 1250 μmol h⁻¹ g⁻¹, which is 1.5 and 5.7 times higher than those of the Pd/g-C₃N₄ and Ag/g-C₃N₄ photocatalysts, respectively. The high activity of the Pd–Ag/g-C₃N₄ photocatalyst was attributed to the inherent property of palladium metal to quench photogenerated electrons by the Schottky barrier formation mechanism and strong visible light absorption due to the characteristic surface plasmon resonance (SPR) of silver nanoparticles along with the absorption of g-C₃N₄.