Transition-metal and metal phosphide nanoparticles catalyze hydrogen-transfer steps that reduce biomass-derived aldehydes using either gaseous H2 or organic hydrogen donors (e.g., alcohols) and produce valuable chemicals and fuels to replace petroleum derivatives. Here, we study reactions of aromatic aldehydes (furfural, benzaldehyde) on Ru(0001) and P0.4-Ru(0001), a surface representative of the (0001) facet of Ru2P, to determine how the addition of phosphorus influences activation barriers and flux along competing reaction pathways. Although Ru(0001) entirely decomposes furfural to CO, H2, and surface carbon, P0.4-Ru(0001) primarily decarbonylates furfural to form CO and furan. Similarly, benzaldehyde decarbonylates to benzene with a selectivity that is 7-fold greater over P0.4-Ru(0001) than on Ru(0001). These observations are consistent with weaker interactions between adsorbates and P0.4-Ru(0001) than on Ru(0001) that reflect charge transfer from Ru to P that in turn reduces electron back donation from Ru to the adsorbates and leads to selective decarbonylation of aromatic aldehydes over P0.4-Ru(0001). The distribution of product isotopologues from temperature-programmed reactions of selectively deuterated forms of furfural on P0.4-Ru(0001) shows that furan forms by catalytic transfer hydrogenation (CTH) on P0.4-Ru(0001). The rate-determining step that forms furan from a furanyl surface species involves hydrogen transfer, but H atoms transfer directly from either the aldehydic group or the decomposed aromatic ring of the parent molecule and not from H∗ atoms chemisorbed to Ru. These findings show that modifying Ru with phosphorus results in the selective rupture of C-C bond required for decarbonylation while facilitating CTH of reactive intermediates from aromatic aldehydes in the absence of an external hydrogen source.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films