Zn galvanic cell without electrolyte?

[![Experiment shema](https://i.stack.imgur.com/I5uUq.png)](https://i.stack.imgur.com/I5uUq.png)


I performed a classical experiment with Zinc-Copper galvanic cell. The zinc electrode was made from pure zinc wire, the copper electrode was made from pure copper wire, the container was a glass beaker around 100cl. Water used for an experiment was pure, distilled ('demineralized') water you can buy at a gas station.


As a baseline test, I put both electrodes in that pure water **without any electrolytes**. I measured voltage between electrodes as well as current flowing between them.


To my surprise, the measured voltage and current were V = 0.8V I = 0.4mA, without any electrolytes in the water medium.


The classical explanation says that on the cathode hydrogen ions are taking electrons forming hydrogen molecules and that an electrolyte is needed (typically an acid). Moreover, it says that voltage will depend on the pH of the solution.


**How to explain that this cell works even with pure water?**


Additionally:


1. I check that copper is not even required, if I only kept zinc electrode in the water, the cathode could other metal, even barely sunk into water, still giving around 0.7~V potential difference.
2. Adding acid or salt to the water made higher current flowing (up to 2mA), made visible gas bubbles on zinc electrode (and that happens in acidic solution even without current flowing) but the voltage kept to be around 0.8V disregard of the presence of electrolyte or its concentration.


