Process to prepare metal nanoparticles or metal oxide nanoparticles

Abstract

The invention is directed to a process to prepare metal nanoparticles or metal oxide nanoparticles by applying a cathodic potential as an alternating current (ac) voltage to a solid starting metal object which solid metal object is in contact with a liquid electrolyte comprising a stabilising cation. The invention is also directed to the use of the nanoparticles as a catalyst.

1 . Process to prepare metal nanoparticles or metal oxide nanoparticles by applying a cathodic potential as an alternating current (ac) voltage to a solid starting metal object which solid metal object is in contact with a liquid electrolyte comprising a stabilising cation. 
     
     
         2 . Process according to  claim 1 , wherein the liquid electrolyte comprises water. 
     
     
         3 . Process according to any one of  claims 1 - 2 , wherein the metal or metals are chosen from the groups of the Periodic Table of Elements according to IUPAC starting at 3 to and including group 15. 
     
     
         4 . Process according to  claim 3 , wherein the metal is chosen from the group consisting of Y, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Ag, Ta, W, Re, Os, Ir, Pt, Au, Al, Si, Ga, Ge, As, In, Sn, Sb, Te, Tl, Pb and Bi. 
     
     
         5 . Process according to any one of  claims 1 - 4 , wherein the solid starting metal is an alloy of two or more metals. 
     
     
         6 . Process according to  claim 5 , wherein the alloy is chosen from the group consisting of PtNi, PtIr, PtRh, PtRu, PtCo, PtMo, PtAu, PtAg, PtRuMo, PtFe, AuCu, PtCu, PtOs, PtSn, PtBi, CuNi, CoNi, AgCu, AgAu, NiSn and SnAg, SnAgCu. 
     
     
         7 . Process according to  claim 6 , wherein the alloy is a SnAg or SnAgCu alloy. 
     
     
         8 . Process according to any one of  claims 1 - 7 , wherein the stabilising cation is an alkali, alkaline earth, ammonium or an alkyl ammonium cation. 
     
     
         9 . Process according to any one of  claims 1 - 8 , wherein two electrodes are in contact with the liquid electrolyte and wherein one electrode is composed of the solid starting material and wherein only to said electrode a cathodic potential is applied. 
     
     
         10 . Process according to any one of  claims 1 - 9 , wherein the nanoparticles are separated from the liquid electrolyte. 
     
     
         11 . Process according to  claim 10 , wherein separation is performed by means of centrifugal force to obtain a phase rich in nanoparticles and a phase of electrolyte, re-using the electrolyte in the process according to  claims 1 - 9 , diluting the phase rich in nanoparticles with water and redispersion by sonication. 
     
     
         12 . Use of the nanoparticles as obtained by the process according to any one of  claims 1 - 11  as a catalyst. 
     
     
         13 . Use according to  claim 12  as a catalyst in fuel-cell reactions. 
     
     
         14 . Use according to  claim 13  as a catalyst in the oxidation of hydrogen, ethanol, formic acid, ammonia, borohydride and other organic compounds and the reduction of oxygen, nitrates and nitrites. 
     
     
         15 . Use according to  claim 12  as a catalyst for neutralization of exhaust gases. 
     
     
         16 . Use according to  claim 14  as a catalyst for waste water treatment. 
     
     
         17 . Use of the nanoparticles as obtained by the process according to any one of  claims 1 - 11  as an electrochemical sensor. 
     
     
         18 . Use of the nanoparticles as obtained by the process according to any one of  claims 1 - 11  in photovoltaics. 
     
     
         19 . Use of the nanoparticles as obtained by the process according to any one of  claims 1 - 11  as part of a conductive nano ink. 
     
     
         20 . Use of silver nanoparticles as obtained by the process according to any one of  claims 1 - 11  as part of an anti-microbial device or composition. 
     
     
         21 . Lead-free soldering paste comprising nanoparticles as obtained by the process according to any one of  claims 7 - 11 .