Nano-porous ruthenium-palladium and ruthenium-platinum alloys and their application as hydrogenation catalysts

Nano-alloys of platinum or palladium attract considerable attention in several catalytic applications. Specifically, nano-porous alloys of these metals serve as catalysts or gas adsorbents. Still, preparing such nano-porous alloys with precise and well-controlled metal composition is considered a synthetic challenge. Previous studies have shown a new approach for the fabrication of nano-porous metals and alloys with controlled compositions through the chemical reduction of metal complex salts. In this work, we obtained two bi-complex salts as precursors for Ru-Pd and Ru-Pt alloys. Single crystals of these salts were also obtained and structurally characterized using X-ray crystallography. Then, using the mentioned procedure, the following nano-porous metallic materials were prepared: Ru2Pd3 and Ru2Pt3 alloys, pure ruthenium, platinum, and palladium metals. Powder X-ray diffraction analysis determined the crystalline phases of these metallic materials. High-resolution scanning electron microscopy indicated that they assemble as clusters of interconnected nanoscale metallic ligaments separated by pores of similar dimensions. Each cluster preserves the microscale morphology of its salt precursor. Energy-dispersive X-ray spectroscopy measurements enabled the determination of the precise molar ratio between the two metals within the salts and alloys. Focused ion beam tomography enabled the 3D structural representation of the metals and alloys and the determination of their porosity and specific surface areas using geometrical analysis. All the metallic materials acquired more than 60% porosity and more than 50 m2/g of specific surface area. Specifically, Ru2Pd3 alloy acquired the highest values of similar to 91% porosity and a surface area of 386 m2/g. The nano-porous metals and alloys exhibit high selectivity in the catalytic hydrogenation of phenyl-acetylene compared to other non-porous commercial catalysts, implying that their structure improved the selectivity. In addition, the alloys showed high conversions and overall high yields in the same reaction, specifically compared to the pure metals. Subsequently, these results support and extend our previous research and suggest a class of palladium or platinum nano-porous alloys that may serve as new and promising catalysts.(c) 2022 Elsevier B.V. All rights reserved.