NOVELTY - A sulfonated polyetheretherketone/boron orthophosphate composite membrane is synthesized by drying polyetheretherketone in a vacuum oven. The dried product is dissolved in concentrated sulfuric acid at room temperature. The resulting polymer solution is heated, after completing the dissolution of polyetheretherketone. The heated solution is decanted into large excess ice-cold water under continuous stirring. Distilled water is added to the polymer rich part and repeatedly washed until a neutral pH of the polymer lean part is reached. The neutral sulfonated polyetheretherketone is dried.    USE - Sulfonated polyetheretherketone/boron orthophosphate composite membrane for a direct methanol fuel cell (claimed) in a vehicle and a portable device. Can also be used for phosphoric acid fuel cell, molten carbonate fuel cell, solid oxide fuel cell, alkaline fuel cell and proton exchange membrane fuel cell in stationary power devices.    ADVANTAGE - The composite membrane is synthesized in an economical and environmental friendly manner with high efficiency, chemical resistance, proton conductivity, mechanical and thermal stability, and low methanol permeability and wide range of application.    DETAILED DESCRIPTION - A sulfonated polyetheretherketone/boron orthophosphate composite membrane is synthesized by drying polyetheretherketone (5 g) in a vacuum oven at 100 degrees C. The dried product is dissolved in 95-98% of concentrated sulfuric acid (95 ml) at room temperature to suppress the heterogeneous sulfonation. The resulting polymer solution is heated to 47-63 degrees C and held for 3 hours, after completing the dissolution of polyetheretherketone for approximately 1 hour. The heated solution is decanted into large excess ice-cold water under continuous stirring and left overnight, to terminate sulfonation reaction for forming a polymer rich phase and a polymer lean phase. The phases are separated. Distilled water is added to the polymer rich part and repeatedly washed until a neutral pH of the polymer lean part is reached. The neutral sulfonated polyetheretherketone is dried at 100 degrees C overnight.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating a method for synthesizing a sulfonated polyetheretherketone/boron orthophosphate composite membrane.