A liquid electrolyte formed by reacting phosphoric acid (H3PO4) in the liquid state with silicon tetrachloride (SiCl4), thereby forming a fluid suspension. The fluid suspension is heated to yield a liquid electrolyte including phosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), and a particulate solid comprising a silicophosphoric acid, wherein the silicophosphoric acid is an acidic molecular compound including silicon and phosphorus. A concentrated silicophosphoric acid composition prepared by removing most of the liquid from the liquid electrolyte is dissolved in water to yield a homogeneous solution. The homogeneous solution is dried to yield a solid electrolyte. In some cases, the homogenous solution is dried on a substrate to coat at least a portion of the substrate with a proton conductive solid electrolyte. A fuel cell may include the liquid electrolyte, the solid electrolyte, or the coated substrate.