Reciprocal-space and real-space neutron investigation of nanostructured MO2C and WC

• Published in: Solid state sciences 2008-11, Vol.10 (11), p.1499-1510
• Main Authors: PAGE, Katharine, JUN LI, SAVINELLI, Robert, SZUMILA, Holly N, JINPING ZHANG, STALICK, Judith K, PROFFEN, Thomas, SCOTT, Susannah L, SESHADRI, Ram
• Format: Article
• Language: English
• Subjects: Catalytic methods; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of nanofabrication; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Neutron diffraction and scattering; Physics; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2008.03.018

As possible substitute materials for platinum group metal heterogeneous catalysts, high surface area carbides of the early transition metals Mo and W are of great interest. Here we report nanostructured, high surface area Mo2C and WC prepared by decomposing and carburizing ammonium paramolybdate [(NH4)6Mo7O24*4H2O] and ammonium paratungstate [(NH4)10W12O41*5H2O] in flowing 50%CH4/50%H2. Surface areas as high as 52 m2/g for Mo2C and 24 m2/g for WC were obtained, with both structures crystallizing in structures appropriate for catalytic activity. We have studied these materials using a combination of neutron diffraction Rietveld refinement, X-ray photoelectron spectroscopy, surface area measurements, and scanning transmission electron microscopy. In addition, we have used pair-distribution function (PDF) analysis of the neutron total scattering data as a means of establishing the presence of graphitic carbon in the as-prepared materials.