I agree with Senthilkumar - reduce the scan speed to say 1 mV/s, and then I guess you will be able to see your reduction peaks. We have made experiments with Ti-oxides which only show extremely broad oxidation/reduction peaks at moderately high scan speeds of around 20 - 50 mV/s, but very sharp and distinct features at 1 mV/s.

I agree with Senthilkumar - reduce the scan speed to say 1 mV/s, and then I guess you will be able to see your reduction peaks. We have made experiments with Ti-oxides which only show extremely broad oxidation/reduction peaks at moderately high scan speeds of around 20 - 50 mV/s, but very sharp and distinct features at 1 mV/s.

I do not think you need to change the scan rate in order to see any reduction or oxidation peak. The problem with cyclic voltammetry is that it is conducted at stagnant conditions. You can only see peaks if the reaction the electrochemical reaction is slow (low activity) but if the material under investigations (a special catalyst for oxygen reduction reaction or a cathode for Li ion battery) is very active (fast electrochemical reaction), then diffusion limitation sets on and control your reaction. This is because oxygen (for example, in the case of oxygen reduction reaction) will be consumed at the surface (for an electrode containing very active catalyst) faster than its rate of arrival to the reaction surface. In that case add a magnetic stirrer to your there electrode setup and see what happen?

I do not think you need to change the scan rate in order to see any reduction or oxidation peak. The problem with cyclic voltammetry is that it is conducted at stagnant conditions. You can only see peaks if the the electrochemical reaction is slow (low activity) but if the material under investigations (a special catalyst for oxygen reduction reaction or a cathode for Li ion battery) is very active (fast electrochemical reaction), then diffusion limitation sets on and control your reaction. This is because oxygen (for example, in the case of oxygen reduction reaction) will be consumed at the surface (for an electrode containing very active catalyst) faster than its rate of arrival to the reaction surface. In that case add a magnetic stirrer to your there electrode setup and see what happen?

What working electrodes are you using for your studies? It could be that the analyte diffusion gradient at the surface of the electrode is masking your peaks. If you have access to microelectrodes, either in an array or individually, and are in a position to miniaturise the rig you're using, this can help with investigating diffusion limited reactions.

I agree that a stirred system could improve your curves appearance, bear in mind though that this could also introduce a lot of noise - it's worth trying though, for your own investigations!

By all means, change your scan rate - however I do not believe that this will improve your traces. It is diligent to try this though for your own scientific records.

2 electrode systems probably don't show the peaks due to a lack of resolution. In studies using higher voltages and currents (relative to the the size of your electrodes) the reference electrode can begin to carry too much current. This is not ideal, as that point at which your baseline potential is quantified will alter and the resolution/reliability of your system will be reduced.

I'd refer you to this book too as it helped me a lot with getting to grips with electroanalysis - hardly bedtime reading, but an excellent primer going through first principles all the way through to complex multivariate analyses and modelling.

Highly recommended reading.

http://www.amazon.co.uk/Electroanalysis-Oxford-Chemistry-Primers-Christopher/dp/0198548168

In my modest opinion, If you see Ni oxide peaks with the three-electrodes configuration and not with the two electrode configuration... is simply due to electrochemical losses of the entire cell, even if you use a strongly conducting solution like a 6M KOH. So, i recommand the use of a three-electrode cell, with a Luggin capillary for the reference electrode.

As a "test experiment", you could make a CV with a two-electrode configuration, and put a reference electrode in the same cell, measuring separately (high impedance voltmeter) the potential difference between the reference and the working. It may be that you don't even reach the needed potential for the development of the redox couples and peaks. This might be due to the high surface area of the Ni electrode.

The choice of the electrolyte is another question. Since Ni oxides (and hydroxides) are stable only in neutral and caustic solutions, you should use these electrolytes. Normally, for electrocatalyst evaluation, 1M NaOH (or KOH indifferently) are sufficient. If you use acids (say

Thanks everyone for their input. I'll take into consideration all of your points!

Cyclic voltammetry can be used without rotation for anodic reaction. But if you look at the literature cyclic voltammetry was used to compare different efficiency of catalytic surfaces which undergo purely cathodic reaction such as oxygen reduction reaction at the cathode of many type of fuel cells and batteries. Cathodic reactions undergo reduction

. In cyclic voltammetry, the Randles-Sevcik equation (1) describes the effect of scan rate on the peak current. For example for a simple redox reaction such as the ferrocene/ferrocenium couple, the peak current measured depends not only on the concentration and diffusional properties of the electro-active species but also on scan rate.

(1) P. Zanello, "Inorganic Electrochemistry: Theory, Practice and Application" The Royal Society of Chemistry 2003.