[Markobar]

Hi all,

My background is not chemistry and I'm new to the forum too, sorry if I'm not clear enough.

I'm looking for a simple bistable and reversible electrochemical reaction that changes color.

Something like:

1) liquid in a glass with two electrodes that when applied a voltage between them, the liquid changes color.
2) When the power is removed, the new color remains (at least for a few minutes/hours).
3) When a negative voltage is applied, the liquid color changes to the original color and remains when power is removed.
4) It's possible to repeat this process many times.

It would be ideal if the chemical components were easy to get and non toxic (if possible).
The colors don't matter at all (transparent to red, blue to green, orange to white, anything really).

I hope the question makes sense!

Thanks a lot!

[Enthalpy]

Maybe. Electrochemical reactions are known that change colours. Like potassium ferro- versus ferri-cyanide (that one can be reversible). Or electrolysis that produces a base, and phenolphthaleine that changes its colour then. And many more.

You might want to check my old patent (public domain now) there
https://patents.google.com/patent/EP0564012A1/pt-PT
it's very thin rather than a liquid in a glass, and this lets the cell change its colour with little current.

I did NOT develop it and ignore how many times it works (and even whether it works at all...). But I got inspired by windows that were to become opaque electrically if sunlight was considered too strong, and maybe these people did investigate more.