Facile in situ formation of high conductive Ag and Cu_xO_y composite films: a role of aqueous spray combustion

In the present contribution, in situ formation of low-temperature high conductive composite films composed of pure silver and oxides of copper (Cu_xO_y where, x = y = 1 for CuO and x = 2, y = 1 for Cu₂O), are presented through spray combustion with a balanced stoichiometric redox reaction. High electrical conductivity (~ 7.8 × 10⁵ S/cm) was retained in the composite film at an annealing temperature of 170 °C with matrix silver phase being 50% by volume. Whereas electrical conductivity of spray combustion processed pure silver is found to be ~ 2 × 10⁶ S/cm. In situ formation of the composite film directly from the silver and cupric nitrate aqueous precursor solution through spray combustion proves it to be compositionally tunable with minimal usage of noble metal. Presence of Ag and Cu_xO_y is confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The ratio of Cu¹⁺/Cu²⁺ in the composite is found to be 0.54 and 0.43 at an annealing temperature of 170 °C and 400 °C respectively. The transformation of Cu₂O to CuO is highly a thermally activated phenomenon; as the vacancy driven electrical conductivity is more in Cu₂O than CuO, stabilization of Cu₂O at a lower temperature is desired. The composite electrode can have potential applications in optoelectronics, printed electronics and catalysis.