On the Role of Support in Metallic Heterogeneous Catalysis: A Study of Unsupported Nickel–Cobalt Alloy Nanoparticles in Ethanol Steam Reforming

(Co, Ni) bimetallic nanoparticles have been prepared by reducing Ni and Co chloride solutions with sodium borohydride. The obtained materials have been characterized as cast and/or after annealing by means of XRD, magnetic measurements, IR spectroscopy, FE-SEM and TEM microscopies. The resulting nanomaterials, originally amorphous, crystallize into the cubic structure cF4-Cu as homogeneous (Co, Ni) solid solution alloy and with the additional presence of Boron containing phases due to the residual preparation impurities. The bimetallic nanoparticles are active in ethanol conversion in the presence of steam. For low Boron catalysts, the addition of Nickel to Cobalt nanoparticles improves the catalytic activity in ethanol steam reforming allowing yields as high as 87% at 773 K, at high space velocities (GHSV 324,000 h−1). The performances of the catalytic unsupported nanoparticles with a Ni/Co atomic ratio equal to 0.26 appear to be better than those of conventional supported catalysts. The state of Boron impurities affect catalytic activity of bimetallic (Co, Ni) NPs. Carbonaceous materials, such as carbon nanotubes and graphitic carbon, form on the catalyst surface upon reaction.