I am working for PEM fuel cell cathode material. I am confused regarding the onset potential determination for my catalyst (CV attached, fig 1 is complete CV while fig 2 is its zoom image for clear understanding of change in reduction curve direction) and also why the reduction starts from 0.8e-4 A instead of 0 A. I performed this CV in calomel electrode under oxygen in 0.5M H2SO4.
i) If I use Argon and overlap both the graphs then probably the curves start to separate at around 0.58V.
ii) I have read in some discussions to consider the onset potential at which current density approaches 0.1mA/cm2 while in other discussion, I have read to consider 20microA/cm2 as onset potential. If I plot current density instead of current only, then in first case (0.1mA/cm2), it would be 0.785V while in second case (20microA/cm2), it would be 0.775V
iii) If I only consider the point from where curve starts to change the direction of reduction peak, it would be 0.64V or 0.56V iv) if I draw tangents then this would be around 0.5V. So please help me in i) analyzing onset potential ii) guide me why there is positive current in the reduction peak iii) i also don't know what does the background correction mean and should I need to do it for my CV? All potentials are measured in SCE.