Humic acid-assisted synthesis of Ag/Ag2MoO4 and Ag/Ag2WO4 and their highly catalytic reduction of nitro- and azo-aromatics

Abstract Herein, Ag/Ag2MoO4 and Ag/Ag2WO4 have been prepared via a humic acid-assisted precipitation-calcination process and used as catalysts for the hydrogenation reduction of nitro- and azo-aromatic compounds. The Ag/Ag2MoO4 and Ag/Ag2WO4 composites were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) and Raman spectroscopies, UV–vis-NIR diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption analyses. Metallic Ag nanoparticles were in situ generated during the annealing process and spatially confined in the Ag2MoO4 or Ag2WO4 matrix, which effectively inhabited the particle agglomeration of silver. The Ag/Ag2MoO4 and Ag/Ag2WO4 catalysts displayed good performance toward the hydrogenation reduction of 4-nitrophenol, 2-nitroaniline, and rhodamine B in terms of rapid conversion and long term durability.