title: Laser synthesis, structure and chemical properties of colloidal nickel-molybdenum nanoparticles for the substitution of noble metals in heterogeneous catalysis.
abstract: Platinum and iridium are rare and expensive noble metals that are used as catalysts for different sectors including in heterogeneous chemical automotive emission catalysis and electrochemical energy conversion. Nickel and its alloys are promising materials to substitute noble metals. Nickel based materials are cost-effective with good availability and show comparable catalytic performances. The nickel-molybdenum system is a very interesting alternative to platinum in water electrolysis. We produced ligand-free nickel-molybdenum nanoparticles by laser ablation in water and acetone. Our results show that segregated particles were formed in water due to the oxidation of the metals. X-ray diffraction shows a significant change in the lattice parameter due to a diffusion of molybdenum atoms into the nickel lattice with increasing activity in the electrochemical oxygen evolution reaction. Even though the solubility of molecular oxygen in acetone is higher than in water, there were no oxides and a more homogeneous metal distribution in the particles in acetone as seen by TEM-EDX. This showed that dissolved molecular oxygen does not control oxide formation. Overall, the laser ablation of pressed micro particulate mixtures in liquids offers a combinational synthesis approach that allows the screening of alloy nanoparticles for catalytic testing and can convert micro-mixtures into nano-alloys.
authors.affiliation: Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany; NanoEnergieTechnikZentrum (NETZ), University of Duisburg-Essen, 47057 Duisburg, Germany.
authors.forename: Galina
authors.initials: G
authors.lastname: Marzun
authors.affiliation: Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Levish
authors.affiliation: Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany.
authors.forename: Viktor
authors.initials: V
authors.lastname: Mackert
authors.affiliation: Aalto University, Department of Chemistry, P.O. Box 16100, FI-00076 Aalto, Finland.
authors.forename: Tanja
authors.initials: T
authors.lastname: Kallio
authors.affiliation: Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany; NanoEnergieTechnikZentrum (NETZ), University of Duisburg-Essen, 47057 Duisburg, Germany. Electronic address: stephan.barcikowski@uni-due.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Barcikowski
authors.affiliation: Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany; NanoEnergieTechnikZentrum (NETZ), University of Duisburg-Essen, 47057 Duisburg, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Wagener
keywords: Alloys; Colloids; Hydrogen evolution; Laser ablation; NiMo; Oxygen evolution; Water splitting