A system for providing hydrogen, comprising: a first electrochemical cell or cell stack comprising a first membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, an inlet for a first gas that comprises hydrogen in fluid communication with the anode side of the first electrochemical cell or cell stack, and an outlet in fluid communication with the cathode side of the first membrane electrode assembly; a second electrochemical cell or cell stack comprising a second membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, a water inlet in fluid communication with the second membrane electrode assembly, and an outlet in fluid communication with the cathode side of the second membrane electrode assembly; and a controller in communication with the first and second electrochemical cells or cell stacks, configured to receive a hydrogen demand signal and: (i) when the hydrogen demand signal is greater than zero and the first gas is not available at the first electrochemical cell or cell stack inlet, to operate the second electrochemical cell or cell stack, and (ii) when the hydrogen demand signal is greater than zero and the first gas is available at the first electrochemical cell or cell stack inlet, to operate the first electrochemical cell or cell stack as a primary hydrogen source and to controllably operate the second electrochemical cell or cell stack as a secondary hydrogen source in response to the hydrogen demand signal and/or the hydrogen output of the first electrochemical cell or cell stack. wherein the proton exchange membranes of the first and second electrochemical cells or cell stacks each comprise an ionomer. a first electrochemical cell or cell stack comprising a first membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, an inlet for a first gas that comprises hydrogen in fluid communication with the anode side of the first electrochemical cell or cell stack, and an outlet in fluid communication with the cathode side of the first membrane electrode assembly; a second electrochemical cell or cell stack comprising a second membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, a water inlet in fluid communication with the second membrane electrode assembly, and an outlet in fluid communication with the cathode side of the second membrane electrode assembly; and a controller in communication with the first and second electrochemical cells or cell stacks, configured to receive a hydrogen demand signal and: (i) when the hydrogen demand signal is greater than zero and the first gas is not available at the first electrochemical cell or cell stack inlet, to operate the second electrochemical cell or cell stack, and (ii) when the hydrogen demand signal is greater than zero and the first gas is available at the first electrochemical cell or cell stack inlet, to operate the first electrochemical cell or cell stack as a primary hydrogen source and to controllably operate the second electrochemical cell or cell stack as a secondary hydrogen source in response to the hydrogen demand signal and/or the hydrogen output of the first electrochemical cell or cell stack. (i) when the hydrogen demand signal is greater than zero and the first gas is not available at the first electrochemical cell or cell stack inlet, to operate the second electrochemical cell or cell stack, and (ii) when the hydrogen demand signal is greater than zero and the first gas is available at the first electrochemical cell or cell stack inlet, to operate the first electrochemical cell or cell stack as a primary hydrogen source and to controllably operate the second electrochemical cell or cell stack as a secondary hydrogen source in response to the hydrogen demand signal and/or the hydrogen output of the first electrochemical cell or cell stack. wherein the proton exchange membranes of the first and second electrochemical cells or cell stacks each comprise an ionomer.