Dear Dr Pierluigi Traverso Thanks so much for your reply. The catalysts analyzed were the fresh catalysts; a combination of Cu and Zn on mesoporous silica. I will go through the papers you recommended. Thank you so much

Perhaps it is due to some differential charging effects due the distribution of copper oxides in areas of different conductivity.

A low binding energy due to a charging effect would be somewhat odd because charging usually leads to increased binding energies. An initially negatively charged reservoir area should vanish for a long enough exposure time.

In general, if there are some differential charging effects, each XPS peak may be splitted into two, one for the element in the conductive region and the other one for the same element in the insulating region. I wonder how is the shape of the C1s peak

Dear Dr S. Feliu Jr I have attached the C1s peak. It looked fairly normal and i wasnt able to find any other resolvable peaks

Dear Opeoluwa Fasanya

Thank you for attaching the C1s peak.I agree. In contrast with the O1s and Cu2p XPS peaks, it looked fairly normal.

Kind Regards.

Without seeing the raw data to assess the noise, it's hard to judge whether the small peak at 926 is really justified. Sometimes there's a tendency to "overfit" the data. Also, did you fit the data with doublets with fixed separation and intensity ratios, or as a series of uncorrelated single peaks?

First, I would suggest to verify that your instrument is correctly calibrated by measuring sputter-cleaned Cu metal surface. You may have problems with non-linearity of the binding energy scale.

Second suggestion - did you by any chance use the charge neutralization during measurement? This may lead to overcompensation and "too low" binding energies.

Dear G. Greczynski Thanks so much for your suggestion. I have sent your suggestion to the scientist who will carry out the analysis. We agreed that something is definitely off somewhere. I have spent time reading your article on challenges that arise with calibrating with the C1s peak. Its quite enlightening. We will attempt recalibration and see how the results look

Dear George Parks Please find attached the vamas file that was generated. I used a series of single uncorrelated peaks

That data looks to be charging based on the VAMAS file - all peaks look to be behaing the same way - Si so the neutalisation is poor. Note also your backgrounds in the VAMAS file and Sensitivity factors are seriously worrying as is the lack of using contraits for doublet pairs! Why use a poylmer tougaard background on a metal peak for example?

Hi David J. Morgan Thanks so much for weighing in. Its a bit of a learning curve for me with regards to XPS analysis. Can you please recommend any text on appropriate backgrounds for metals. I concluded with the analyst that the sample would have to be run again.