How well did it work?

A series of bimetallic PdCu catalysts were tested for the selective hydrogenation of furfural under mild conditions. The catalyst morphology and electronic properties were thoroughly studied utilising XRD, XPS, STEM, EXAFS, XANES, TPR and ICP-OES. Catalyst characterisation confirms that Pd atoms were atomically dispersed on the host copper nanoparticle surface, confirming the formation of a single atom catalyst. The augmentation of the copper surface with trace amounts of Pd (0.0067 wt%) was found to improve the host Cu catalyst to that of a Pd catalyst in terms of normalised furfuryl alcohol production. Also, when compared to the Cu100 catalyst 1.7 and 1.9 times in performance is observed in the conversion and Cu TOFs, respectively. Finally, when compared against the literature, it was found that these materials are, to the best of our knowledge, the most competitive atom efficient catalysts implemented for the selective hydrogenation of furfural to furfuryl alcohol, especially when using both low H2 pressure and reaction temperature.

Metal Speciation

XAFS was used to identify the formation of Cu-Pd bonds and confirm the creation of single atom sites

Metal Site Identification

STEM revealed small metal nanoparticles, while incorporation of Pd via galvanic replacement imparted little effect upon NP size.

Reduction of Catalysts

TPR data shows effect of decreasing reduction temperature upon addition of Pd. XRD reports no large metal crystallites.

Catalytic Behaviour

TOFs reveal clearly that the incorporation of single atom sites on the Cu NPs increases catalytic activity significantly

Our awesome features

How did XPS help?

While XAFS identified the presence of Cu-Pd bonds, it is unable to distinguish surface and bulk - Pd atoms need to be at the surface for these systems to perform! XPS enabled us to observe surface systems at work.

Auger parameter (a')

The auger parameter is required for accurate analysis of copper by XPS.

Energy changes to a'

Electron withdrawal from NP supports impact electron screening, which is reflected in the auger parameter

Surface oxidation state

XPS and auger analysis identified a level of surface Cu2O formation

Dispersions

XPS was used to derive dispersions, complementary to STEM analysis

Spent Catalyst

Analysis of the spent material determined some sintering and oxidation

What does this mean?

XPS was able to identify chemical speciation as a function of spatial locale and as such probe the active regions of the prepared catalyst