Advancement of a hydrogen economy requires establishment of a whole supply chain including hydrogen production, purification, storage, utilization, and recovery. Nevertheless, it remains challenging to selectively purify hydrogen out of H2-containing streams, especially at low concentrations. Herein, a novel protonic ceramic electrochemical cell is reported that can sustainably separate pure H2 out of H2-diluted streams over the temperature regime of 350-500 °C by mildly controlling the electric voltage. With the Faraday's efficiency above 96%, the measured H2 separation rate at 0.51 V and 500 °C is 3.3 mL cm-2 min-1 out of 10% H2 - 90% N2, or 2.4 mL cm-2 min-1 out of 10% H2 - 90% CH4 taken as an example of renewable hydrogen blended in the natural gas pipelines. Such high hydrogen separation capability at reduced temperatures is enabled by the nanoporous nickel catalysts and well-bonded electrochemical interfaces as produced from well-controlled in situ slow reduction of nickel oxides. These results demonstrate technical feasibility of onsite purification of hydrogen prior to their practical applications such as fuels for fuel cell electric vehicles.
Keywords: distribution of relaxation time (DRT); electrochemical hydrogen pump; hydrogen evolution; hydrogen oxidation; hydrogen separation; protonic ceramic electrochemical cell (PCEC); symmetrical fuel cells.