Rob presented the first results of the EPSRC grant: EP/I038748/1 at the RSC Postgraduate Symposium on Nanotechnology in Birmingham
This figure is from the talk and shows how graphite surfaces are modified by treatment with acid. The work has been submitted to Carbon for publication.
Carbon catalyst supports are usually treated with acid before the adsorption of the active phase and often reactivated with a similar treatement. But what effect does the acid treatement have on the carbon and how does it influence the adsorption of the active phase? Highly oriented pyrolytic graphite (HOPG) samples were treated with dilute HCl and HNO3 under ambient conditions and examined with AFM, STM and XPS to explore this issue. Raised features were formed on the HOPG surface after acid treatment. These protrusions were typically 4-20 nm in height and between 10 to 100 nm in width, covering 5% to 20% of the substrate for acid concentrations between 0.01 and 0.5 M. Both width and surface density of the features increases with acid concentration but the heights are not affected. STM images show that the graphite lattice extends over the protrusions indicating that the features are “blisters” on the surface rather than deposited material, a view that is supported by the XPS. We propose that penetration of the acid at defective sites leads to a decrease in the interplanar van der Waals forces and a local delamination. Deposition of Au onto the acid treated surfaces showed fundamental differences in the way Au is adsorbed depending on which acid is used. AFM showed that HCl pre-treatment facilitates the formation of significant independent Au clusters on top of the delamination sites whereas HNO3 pre-treatment results in rather larger less dispersed structures. XPS revealed that HCl enables greater Au deposition thanHNO3, and also increases the presence of Au0 state on the surface