[FWD from LinkedIn] relation between working function and corrosion potential

Teddy Huang posted on Mon, Mar 16 2015 12:47 AM

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Marjan KashfipourResearch assistant at The University of Akron

Hi all, is there anybody who can explain the relation of working function which is measured during KPFM mode of AFM and corrosion potential of the sample? I'm confused a little bit about it, some papers assume higher potential means more noble corrosion potential and some assume the other way.

Thomas Mueller

Director, AFM Development Applications at Bruker Nano Surfaces

Hi Marjan - I think you are posing an excellent question and I really just have a small comment from the angle of the KPFM measurement. While KPFM measurements can be performed in a number of ways, incl AM or FM detection or PeakForce feedback to maximize resolution and sensitivity, they are usually performed in air, and for the purpose of interpreting the results as workfunction, a physical picture is invoked where an electron is lifted to the vacuum level. Not the same as what happens in solution where the electrochemical potential is defined and ions are being solvated and such. That being said, correlation between the two measurements has been reported, e.g., JECS 145, 2285, 1998, and to answer your question, in that paper it was higher workfunction correlating to more positive (more 'noble') electrochemical potential, as one might expect. Note that how the workfunction difference relates to KPFM measurement output depends on voltages polarities / sign conventions / biasing tip vs sample. Hope this answer is useful, don't hesitate to contact me privately for more information on KPFM.

Teddy Huang