From the "supplemental information" [1] part of the actual paper [2], the levels of current are measured in μA and tenths of volts (ie. in the order of μW of power).

What is fully unclear to me is how (or whether) that power can be harvested and put to any electrical use. Or perhaps it is only of chemical interest?

[1] https://www.cell.com/cms/10.1016/j.joule.2023.08.006/attachm... [2] https://www.cell.com/joule/fulltext/S2542-4351(23)00352-5?_r...