how to make electrohemical cell? I have found some examples but they are all with Cu and Zn , and my teacher told us that we mustnt make cell with these two elements. Could you plesase help me

Push a strip of steel(iron) and a strip of aluminum into a lemon. A strip of Cu and one of Zn works well in a lemon. Iron and aluminum should do just as well. Make sure the aluminum is shiny. If it isn't shiny, buff it up with steel wool. If you have trouble finding strips of steel, use a tin can lid (like food tin can). Just make sure the inside of the can isn't coated with plastic.