NOVELTY - A hydrogen stream is purified by introducing a contaminated hydrogen stream to an anode of an electrochemical cell; applying a voltage across a membrane assembly of the cell; oxidizing the hydrogen to form protons which are moved across the membrane to a cathode of the cell; and recombining the protons to form a recombined hydrogen stream.    USE - The invention is used for purifying a hydrogen stream.    ADVANTAGE - The invention provides an efficient hydrogen purification process that can be readily employed in various systems e.g. a fuel cell. The purifier is simplified, efficient, cost effective and pressurizes hydrogen for commercial use if desired.    DETAILED DESCRIPTION - Purification of a hydrogen stream includes:    (a) introducing a contaminated hydrogen stream to an anode (103) of an electrochemical cell;    (b) applying a voltage across a membrane assembly of the cell;    (c) oxidizing the hydrogen to form protons (105) which are moved across the membrane to a cathode (107) of the cell; and    (d) recombining the protons to form a recombined hydrogen stream.    An electrolyte membrane (108) is disposed between the anode and the cathode to form the membrane assembly. The voltage is below an electrolysis voltage that causes electrolysis under operation conditions of the assembly.    An INDEPENDENT CLAIM is also included for a method of operating a fuel cell system. The method includes:    (i) reforming hydrocarbon fuel stream to produce a contaminated hydrogen stream;    (ii) purifying the contaminated hydrogen stream;    (iii) introducing a recombined hydrogen stream formed from purification to a fuel cell anode;    (iv) introducing an oxygen containing stream to the fuel cell cathode; and    (v) producing electricity by oxidizing the reformed hydrogen (109) to form electrons and fuel cell protons.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of an electrochemical hydrogen purifier.    Anode (103)    Protons (105)    Cathode (107)    Membrane (108)    Reformed hydrogen (109)