If you could clarify what your system is exactly, that'd be helpful - presumably this means you're getting a negative potential and can draw current off of that. Especially in an H2/O2 type system, you shouldn't be getting any negative potentials unless there's something that's really strongly reducing or oxidizing in one of your electrodes, to the point where the catalyst wouldn't be air/water-stable. My test stations (Scribner) don't allow you to draw a negative current per se (you could reverse the sensor electrodes to switch it to a positive potential then draw current, but the issue hasn't come up). Even with something strongly reducing/oxidizing, drawing any meaningful current would be unlikely since the overpotential for H2 and/or O2 emission is typically rather high and the reaction would slow/stop quickly once the oxidizing or reducing agent was consumed.

Hi Benjamin,

Thank you for your response!  I agree with what you have stated that I should also observe a negative potential but it may be due to the MEA I am using has been utilized for organic hydrogenation.  I am using H2/O2 setup to help diagnose my MEA's performance after exposure to crotonaldehyde. 

To clarify, I am actually getting a positive potential (OCP is ~0.8V) but when I apply 0.6V or 0.2V, I obtain a negative current.  I am using a pstat (Autolab) to apply the potential; the anode is the counter and reference, while the cathode is the working electrode.  I was wondering if it is possible to get a negative current if a different reaction is taking on the cathode?

The negative current is only a transient ?

In case that is only a transient (time

It occurs for the duration of the applied potential.  I have been alternating between 0.6V and 0.2V for 2 minutes each for at least 4 hours.  

Can you show, please, some (>1) cycles of LSV (VLow=0.0, VHigh=0.8) for 2 rates (1mV/s, 10mV/s) ?

Have you run a non-exposed reference under the same conditions? At that time-scale, it must be normal operation, especially if you're achieving relevant current densities to your reference. To get a positive potential, you've got the working electrode connected to the cathode, and I'm pretty certain you're just getting normal current convention for your potentiostat - a positive current is oxidizing whatever's connected to the working electrode - i.e. drawing electrons out of the cathode. So, since you're reducing at the cathode to drop the potential, moving electrons into the cathode, it's a negative current, just like the HER when you do a CV.

Hi all,

Thank you for your responses!  I realized that the issue is using a PSTAT that does not have the current and voltage range required for a fuel cell.

Sarah Carl Hi Sarah, I'm currently having the same issue with using Pstat (Autolab). Could you please let me know how you solved this problem if you still have the data? Thank you!

Jisu Lim Sarah Carl Hii Sarah and Lim, I am currently working on polymer electrolytes for PEMFC application. While analyzing the performance of the constructed cell setup using I-V polarization graph, I am across the positive potential and negative current. Is it right?. What will be the reason for this negative current? How to rectify the same?

Kindly guide me.

Thanks in advance.