Disclosed herein is a membrane-electrode assembly containing: a gastight, selectively proton-conducting membrane which has a retentate side having an anode and a permeate side having a cathode; a voltage source for generating a potential difference between the anode and the cathode; an anode catalyst having a catalytically active material on the retentate side; and a cathode catalyst having a catalytically active material on the permeate side, in which the cathode catalyst has a smaller amount of catalytically active material than the anode catalyst. The present disclosure also includes a reactor containing the membrane-electrode assembly, and a process for separating off hydrogen using the membrane-electrode assembly.