Our lab work clearly shows that with the correct physical configuration some redox reactions can be harnessed for their electrical work. In each case, despite particulars which may vary, functioning galvanic or voltaic cells have some common features:
- species which can be oxidized and reduced
- an electrolyte to connect these species
- some way to electrically connect the reducing and oxidizing agents
That's pretty general. But it needs to be because an amazing variety of materials can be used to generate electric potentials.
Correctly constructed galvanic cells will "pump" electrons through an external circuit until the reactions within them reach equilibrium. To keep the discussion simple and to illustrate what happens in galvanic cells, we can adopt the classic configuration of 2-compartment cells with dissimilar metals. But you should keep in mind that other combinations are possible and often very important.