HELP - Chemistry EE Sources - Ligands and potential difference

[hamburgertheplant]

Hi!

So I'm doing an extended essay in chemistry, more specifically, electrochemistry. I am researching voltaic cells, and the effect of ligand substitution has on them. Basically, my experiment is that I add some designated solutions to Copper sulphate (I added EDTA, HCl and Ammonia), and then use this new solution to make a voltaic cell using a copper strip. This changes the potential difference of the cell, and basically, I am researching how this might improve voltaic and chemical batteries to increase effectiveness.

Obviously, along the line, I should have to explain why this happens, right?

The only problem is, that I can't find an answer. I had a lot of research on the substitution of ligands in a solution, and on voltaic cells, but very little on the combination of the two. I am struggling to write a first draft when I can't explain why this even happens. 

Am I expected to figure out the answer on my own? All the research papers I have found which investigate a similar subject are either too complicated for me to understand, or I don't have access to. At this rate, I just need to find an answer to why the potential difference changes, so at least I can start my research from a different angle. 

I generally type into google scholars something like "The effect of changing ligands on electrode potential", or something similar, but no relevant results come up.

Does anyone have any suggestions for what I should research?

Or does anyone have some good scientific websites where I am more likely to find an answer?

Or, does anyone have any other suggestions for what I should do to find an answer to my question?

Thanks so much,

hamburgertheplant