We present a method of co-generating hydrogen peroxide and electrical power via the two-electron cathodic reduction of oxygen in a H-2/O-2 proton exchange membrane fuel cell (PEMFC). The cell uses a continuous flow of carrier water through its cathodic chamber to remove the hydrogen peroxide product at a neutral pH. To improve the co-generation of electric power and hydrogen peroxide, a number of different cathode configurations, using both four- and two-electron oxygen reducing electrocatalysts, were constructed and examined. With a bifunctional cathode structure consisting of side-by-side carbon-supported Pt- and Co-C-based catalyst layers, and a carbon-based micro-porous layer (MPL), a hydrogen peroxide generation flux of 8 A mu mol h(-1) cm(-2) is achieved. The corresponding power density is about 133 mW cm(-2). The co-generation of power and hydrogen peroxide could be used in a variety of applications, including the on-site production of hydrogen peroxide for water treatment by advanced oxidation processes. [GRAPHICS] .