Photocatalytic Decomposition of an Azo Dye Using Transition-Metal-Doped Tungsten and Molybdenum Carbides

Busisiwe Petunia Mabuea; Hendrik Christoffel Swart; Elizabeth Erasmus

doi:10.1021/acsomega.2c01727

Photocatalytic Decomposition of an Azo Dye Using Transition-Metal-Doped Tungsten and Molybdenum Carbides

ACS Omega. 2022 Jun 24;7(27):23401-23411. doi: 10.1021/acsomega.2c01727. eCollection 2022 Jul 12.

Authors

Busisiwe Petunia Mabuea¹, Hendrik Christoffel Swart¹, Elizabeth Erasmus²

Affiliations

¹ Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
² Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.

Abstract

The preparation, characterization, and photocatalytic application of tungsten or molybdenum carbides (Ni-WC, 1, Co-WC, 2, Ni-MoC, 3, Co-MoC, 4, NiCo-WC, 5, NiCo-MoC, 6, NiFe-WC, 7, and NiFe-MoC, 8) doped with transition metals (Fe, Co, and Ni) are reported. These transition-metal carbide (TMC) particles show that the submicrometer globular particles agglomerated to form larger particles, with smaller crystallites present on the surface of the large particles. These crystallite sizes range between 4 and 34 nm (as calculated from X-ray diffraction data) depending on the metal dopant and type of carbide. Oxidation of the metal carbides is evident from the two sets of photoelectron lines present in the X-ray photoelectron spectroscopy (XPS) of the W 4f area. The Mo 3d spectra reveal four sets of photoelectron lines associated with oxidized MoO₂ and MoO₃ as well as Mo²⁺ and Mo³⁺ associated with MoC_1-x . The XPS of the dopant metals Ni, Co, and Fe also show partial oxidation. The photocatalytic decomposition of Congo red (an azo dye) is used as a model reaction to determine the photocatalytic activities of the transition-metal carbides, which is related to the TMCs' optical band gap energies.