Electrochemical method for producing globules of ultrasmall rhodium nanoparticles with poly(N-vinylpyrrolidone) bound to the surface of nanocellulose fibers

The study concerns the preparation of Rh nanoparticles (NPs) by room-temperature, methyl viologen (MV2+) mediated electrochemical reduction of RhCl3 in the presence of poly(N-vinylpyrrolidone) (PVP, 40000 Da) and nanocellulose (NC, d = 57 +/- 36 nm) at a controlled potential of generation of MV center dot+ radical cations in aqueous medium. When a theoretical amount of electricity is passed, the mediator is not consumed, while Rh-(III) is quantitatively reduced to Rh-(0). The reduction results in the Rh@PVP (141-191 nm in size) and Rh@PVP/NC nanocomposites dispersed in the solution bulk. The Rh@PVP/NC nanocomposite represents PVP globules (42 +/- 13 nm in size) with encapsulated ultrasmall spherical Rh NPs (1.3 +/- 0.4 nm in size) bound to the surface of NC fibers. The Rh nanocomposites exhibited high catalytic activity in the model reaction, viz., reduction of p-nitrophenol with sodium borohydride in aqueous medium. The catalytic activity increased in the presence of cetyltrimethylammonium chloride (CTAC).