Copper nitride/silver nanostructures synthesized via wet chemical reduction method for the oxygen reduction reaction

This work presents attempts to synthesize silver-doped copper nitride nanostructures using chemical solution methods. Copper(II) nitrate and silver(I) nitrate were used as precursors and the oleylamine as a reducing and capping agent. Homogeneous Cu 3 N/Ag nanostructures with a diameter of ~ 20 nm were obtained in a one-pot synthesis by the addition of the copper(II) salt precursor to the already-synthesized silver nanoparticles (Ag NPs). Synthesis in a two-pot procedure performed by adding Ag NPs to the reaction medium of the Cu 3 N synthesis resulted in the formation of a Cu 3 N@Ag nanocomposite, in which Ag NPs are uniformly distributed in the Cu 3 N matrix. The morphology, structure, and chemical composition of the obtained specimens were studied by TEM, XRD, XPS, and FT-IR methods, while optical properties using UV–Vis spectroscopy and spectrofluorimetry. The band gap energy decreased for Cu 3 N/Ag ( E g = 2.1 eV), in relation to pure Cu 3 N ( E g = 2.4. eV), suggesting the insertion of Ag atoms into the Cu 3 N crystal lattice. Additionally, Cu 3 N and Cu 3 N/Ag nanostructures were loaded on graphene (GNP) and tested as a catalyst in the oxygen reduction reaction (ORR) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The Cu 3 N/Ag-modified GNP hybrid material revealed catalytic activity superior to that of Cu 3 N-based GNP hybrid material and pure GNP, comparable to that of a commercial Pt/C electrode. Graphical Abstract