Provide an example of an electron donor used in chemosynthesis

Chemo synthesis is a process that utilizes chemicals to generate energy by non green plants by conversion of carbon containing molecules such as methane, and nutrients to organic compounds through oxidation of inorganic compounds.
It involves use of electron donors such as hydrogen sulfide or iron which donates electrons to carrier molecules coupled by release of energy.

It was said to have happened by earthquakes, the shifts in the tectonic plates moved everything