Composite reference electrode substrates and relating methods are provided. The composite reference electrode substrate includes a separator portion and a current collector portion adjacent to the separator portion. A method for forming the reference electrode substrate includes anodizing one or more surfaces of a first side of an aluminum foil so as to form a porous separator portion disposed adjacent to a porous current collector portion. The porous separator portion includes aluminum oxide, and the current collector portion includes the aluminum foil. The separator portion and the current collector portion each have a porosity of greater than or equal to about 10 vol. % to less than or equal to about 80 vol. %.