New insights into the synergistic effect in bimetallic-boron catalysts for hydrogen generation: The Co–Ru–B system as a case study
Catalysed sodium borohydride hydrolysis is a high-potential method to produce hydrogen for portable applications. Co–B catalysts are the most chosen because they are easily prepared, cheap and efficient. The addition of small amounts of Ru produces a significant enhancement in catalytic activity.In the present work a series of Co–Ru–B catalysts with variable Ru content was prepared, isolated and characterized. The comprehension of the synergistic effect was achieved trough the incorporation of the nanostructural dimension to the study of surface and bulk chemical states of the involved atoms along the series. It was found that up to 70% (of total metal) atomic content of Ru the catalysts can be considered isostructural to the single Co–B catalyst in the nanoscale. A structural transition occurs in the case of the pure Ru–B material to produce a boron deficient material with higher nanoparticle size. This structural transition together with Co segregation and Ru dispersion play a key role when explaining a [OH−] dependent effect.The inexistence of borate layers in Ru rich catalysts is suggestive in the research for non deactivating catalysts.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Activity for hydrogen generation of Co–B catalysts is enhanced by small amounts of Ru. ► Nanostructure of Co–Ru–B catalysts is related to boron-metal chemistry. ► Co–Ru–B catalysts isostructural to Co–B. Nanostructural transition occurs for Ru–B. ► Cobalt segregation and Ru dispersion explain the synergistic effect. ► The effect is not universal but [OH−] dependent.
Journal: Applied Catalysis B: Environmental - Volume 128, 30 November 2012, Pages 39–47