The Influence of Metal-Doped Graphitic Carbon Nitride on Photocatalytic Conversion of Acetic Acid to Carbon Dioxide

Abstract

Metal-doped graphitic carbon nitride (MCN) materials have shown great promise as effective photocatalysts for the conversion of acetic acid to carbon dioxide under UV–visible irradiation and are superior to pristine carbon nitride (g-C3N4, CN). In this study, the effects of metal dopants on the physicochemical properties of metal-doped CN samples (Fe-, Cu-, Zn-, FeCu-, FeZn-, and CuZn-doped CN) and their catalytic activity in the photooxidation of acetic acid were investigated and discussed for their correlation, especially on their surface and bulk structures. The materials in the order of highest to lowest photocatalytic activity are FeZn_CN, FeCu_CN, Fe_CN, and Cu_CN (rates of CO2 evolution higher than for CN), followed by Zn_CN, CuZn_CN, and CN (rates of CO2 evolution lower than CN). Although Fe doping resulted in the extension of the light absorption range, incorporation of metals did not significantly alter the crystalline phase, morphology, and specific surface area of the CN materials. However, the extension of light absorption into the visible region on Fe doping did not provide a suitable explanation for the increase in photocatalytic efficiency. To further understand this issue, the materials were analyzed using two complementary techniques, reversed double-beam photoacoustic spectroscopy (RDB-PAS) and electron spin resonance spectroscopy (ESR). The FeZn_CN, with the highest electron trap density between 2.95 and 3.00 eV, afforded the highest rate of CO2 evolution from acetic acid photodecomposition. All Fe-incorporated CN materials and Cu-CN reported herein can be categorized as high activity catalysts according to the rates of CO2 evolution obtained, higher than 0.15 μmol/min−1, or >1.5 times higher than that of pristine CN. Results from this research are suggestive of a correlation between the rate of CO2 evolution via photocatalytic oxidation of acetic acid with the threshold number of free unpaired electrons in CN-based materials and high electron trap density (between 2.95 and 3.00 eV).

Ultrafast plasma method allows rapid immobilization of monatomic copper on carboxyl-deficient g-C3N4 for efficient photocatalytic hydrogen production

“…Obviously, by introducing Cu species and -COOH groups into the raw g-C 3 N 4 via the plasma method, the visible light energy harvesting ability of the Cu-pCN-oxalate photocatalyst is greatly promoted so as to enhance the catalytic performance (Shi et al, 2019). The promoted visible light energy harvesting ability of the Cu-pCN-oxalate photocatalyst can be ascribed to the introduction of monatomic copper and carboxyl defects, which regulate the highest occupied molecular orbital (HOMO) of holes and the lowest unoccupied molecular orbital (LUMO) of electrons of g-C 3 N 4 polymer semiconductors by changing the charge balance state of N atoms in the twodimensional plane, leading to a narrowed energy level gap (Eg) (Dou et al, 2019;Sakuna et al, 2022;Liu Y. et al, 2019).…”

Recent Advances in Advanced Oxidation Processes for Degrading Pharmaceuticals in Wastewater—A Review

“…However, visible light also excites some organic pollutants, particularly dyes, leading to their spontaneous photolysis, so that the photocatalytic degradation of the dyes on such visible-light-responsive catalysts competes with their spontaneous photolysis [97,98]. In many studies, it has been pointed out that the incorporation of dopants creates trapping states, accelerating electron-hole recombination and decreasing the photocatalytic activity of the metal oxides and perovskite-type metal oxides [99,100].…”

Chitosan-Grafted Carbon Oxynitride Nanoparticles: Investigation of Photocatalytic Degradation and Antibacterial Activity

“…In addition, the diffusion of metal ions also causes secondary pollution of water resources. In contrast, graphitic carbon nitride (g-C 3 N 4 ), which belongs to a two-dimensional material, has attracted much attention for its potential applications in the degradation of organic pollutants [ 20 ], water splitting [ 21 ], CO 2 fixation [ 22 , 23 ] and biological applications [ 24 ]. The g-C 3 N 4 is composed of carbon and nitrogen elements and synthesized by thermal polycondensation of precursors such as melamine, urea, cyanamide and dicyandiamide [ 25 , 26 , 27 , 28 ], which is facile to be produced on an industrial scale.…”