Br- and I-modified g-C3N4 photocatalysts prepared via novel two-stage technique for hydrogen evolution and photocurrent generation

Abstract

Graphitic carbon nitride (g-C3N4) modified with bromine and iodine was synthesized by a novel two-stage technique that included hydrothermal pre-treatment of melamine and its calcination in a mixture with ammonium halide. Prepared photocatalysts were tested by a set of methods including X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), thermal gravimetric analysis (TGA), low temperature nitrogen adsorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CVA), impedance spectroscopy, and the Mott – Schottky method. All the photocatalysts were studied in the photocatalytic hydrogen production from triethanolamine (TEOA) under visible light irradiation (λ = 428 nm). The most active photocatalyst was prepared from a mixture of 50% NH4I and 50% melamine. Its catalytic activity (2120 μmol g−1 h−1) was 35 times higher than that of the catalyst synthesized by the simple calcination of melamine. The highest short-circuit current density of 2.7 mA/cm2 was obtained with a sample synthesized from the mixture of 80% NH4Br and 20% melamine.