Disclosed is a unitized electrochemical cell sub-assembly having a first separator plate and a second separator plate that each has a first surface. A recess is located in at least one of the first surfaces to define a chamber adjacent the periphery of the plates when the plates face each other. A membrane electrode assembly (MEA) comprising an ion exchange membrane and a pair of gas diffusion layers is disposed on and between each of the first surfaces between the two plates when the plates face each other so that the peripheral edge of the ion exchange membrane is located within the chamber. Also located in the chamber is a non-conductive sealant polymer that seals and joins the first and second plates to each other, and that seals and joins the first and second plates to the edge of the ion exchange membrane. Also disclosed is a fabrication method for making the unitized electrochemical cell sub-assembly.