Ni, NiO, beta-Ni(OH)(2) and Pt nanomaterials are prepared with cathodic contact glow discharge electrolysis (CGDE) in acidic and alkaline media by alternating the Ni and Pt cathode vs. a large Ni anode. The morphological and crystalline characterizations of the products suggest two reaction mechanisms where in the first, metal ions are locally reduced by the high reducing agents generated by the electrical discharges from the cathode, i.e. the solvated electron, the H-center dot radical and secondary species if any. This is supported by CGDE experiments conducted in acidic environment with Ni or Pt cathode that gave Ni-based materials only. The second mechanism for the formation of metals aggregates is due to the cathode material electro-erosion due to the high temperature spots at its surface that lead to the local vaporization of its material and the rapid quenching of the generated powder. This conclusion is drawn after eliminating the source of Ni2+ ions, initially due to the Ni anode dissolution in acidic pH, and conducting the same two previous experiments in concentrated KOH solutions instead. In both arrangements, it is the cathode material that was the source of the synthesized nanoparticles. (C) 2012 Elsevier Ltd. All rights reserved.