Surface (dis)order sleuthing

Now, Plamen Atanassov and colleagues at the University of California, Irvine, introduce a simple method to evaluate the degree of surface crystallinity based on oxygen 1s X-ray photoelectron spectra (noting that the surface region is defined by the penetration depth of the technique). The researchers put forward the ratio between the peak intensity of μ1−O(H) and μ2−O(H) defective oxygen species as a descriptor for surface crystallinity, where higher values correspond to a lower degree of crystallinity. The approach is validated for a set of seven commercially available self-supported iridium oxide catalysts.

The results stemming from the μ1/μ2 descriptor can be complemented with the intensity of the μ3−O species, which correspond to non-defective oxygens in the crystalline rutile bulk structure. Furthermore, the proposed descriptor is comparable to the more common one based on the ratio of Ir^III and Ir^IV peaks from Ir 4f spectra. Finally, the researchers show that there is no correlation between surface crystallinity and intrinsic water oxidation activity in 0.1 M HClO₄ for the present set of commercial catalysts.