Two-Step Mediated Electrosynthesis and Catalytic Activity of Au/Cu2O@poly(N-vinylpyrrolidone) Nanocomposite

Efficient two-step methylviologen (MV 2+ ) — mediated electrosynthesis of a nanocomposite of gold nanoparticles with copper(I) oxide stabilized by a shell of poly(N-vinylpyrrolidone) (Au/Cu 2 O@PVP) was performed in DMF at room temperature at the potentials of MV .+ radical cation generation. At the first step, the mediated reduction of Cu 2+ ions, generated in situ by dissolution of the copper anode, in the presence of dissolved oxygen or with subsequent oxidation with oxygen, leads to Cu 2 O@PVP composite containing Cu(0) and Cu 2 O in a different ratio. In the latter case, the resulting composite is in the form of stable nanoroses. When AuCl is added into the resulting solutions of Cu 2 O@PVP, the partial chemical reduction of AuCl by Cu(0) occurs to form Au(0) and CuCl. At the second step, the electrochemical reduction of AuCl leads to Au/Cu 2 O@PVP nanocomposite not containing Cu(0), but nanoroses are preserved. Cu 2 O@PVP nanoparticles are catalytically inactive in the reduction reaction of p -nitrophenol with sodium borohydride in water, and Au/Cu 2 O@PVP nanocomposites exhibit catalytic activity. In the presence of cetyltrimethylammonium chloride, the catalytic activity of both types of particles sharply increases; in the case of Cu 2 O@PVP, the increase is so high that the catalytic activity becomes the same as for Au/Cu 2 O@PVP.