New ceramic membrane generates compressed H2 from methane and electricity with near-zero energy loss
A team of scientists from CoorsTek Membrane Sciences, the University of Oslo (Norway) and the Instituto de Tecnología Química (Spain) have successfully completed laboratory testing of a ceramic membrane that generates compressed hydrogen from natural gas and electricity in a one-step process with near-zero energy loss.
The research, reported in the journal Nature Energy, builds on 20 years of experience in the development and manufacturing of ceramic membranes at CoorsTek. The membrane—a “protonic membrane reformer” (PMR)—is made from oxides of abundant materials (including barium, zirconia, and yttrium), forming a solid ceramic electrolyte that can transport hydrogen in the form of protons at temperatures from 400 to 900 °C. By applying an electric potential over the ceramic cell, hydrogen is not only separated from other gases but also electrochemically compressed.
The researchers achieved full methane conversion at 800 ˚C by removing 99% of the formed hydrogen, which is simultaneously compressed electrochemically up to 50 bar. A thermally balanced operation regime is achieved by coupling several thermochemical processes.
Herein, we report an electrochemically driven PMR that realizes four process steps simultaneously within a 400μm length scale. First, it extracts hydrogen from the reforming side and shifts a thermodynamically limited reaction sequence towards full conversion of methane; second, it delivers heat to the strongly endothermic reaction through the electrical operation of the membrane—acting as a separator and a compressor; third, it compresses hydrogen directly at the sweep side of the membrane; and last, it produces high-purity hydrogen. The combination of these functions in a single spatially integrated stage confers high overall energy efficiency, process simplicity and compactness.—Malerød-Fjeld et al.
The membrane reformer in the study is a tubular cell, 10 mm O.D., composed of a dense 30-μm-thick BaZr0.8-x-yCexYyO3-δ (BZCY) proton-conducting electrolyte sandwiched between two porous electrodes of BZCY and Ni. At 800 °C and a steam pressure of 1 bar, BZCY exhibits pure proton (H+) conductivity of 10 mS cm−1. By applying a voltage and hence current across the electrolyte, hydrogen is selectively extracted from the inner steam methane reforming chamber, reaching hydrogen production rates of 25 Nml min−1 cm−2 at 4 A cm−2, operating essentially at the theoretical Faradaic limit and with an area specific resistance of 0.4Ωcm2.
Our breakthrough ceramic membrane technology makes it possible for hydrogen-fueled vehicles to have superior energy efficiency with lower greenhouse gas emissions compared to a battery electric vehicle charged with electricity from the grid. The potential for this technology also goes well beyond lowering the cost and environmental impact of fueling motor vehicles. With high-volume CoorsTek engineered ceramic manufacturing capabilities, we can make ceramic membranes cost-competitive with traditional energy conversion technology for both industrial-scale and smaller-scale hydrogen production.—Per Vestre, Managing Director at CoorsTek Membrane Sciences
Although use of hydrogen as an energy carrier for next-generation fuel cell electric vehicles is still limited, hydrogen is already an important molecule for a range of industrial processes from food processing to manufacturing of glass and semiconductors, with ammonia-based fertilizers as the single largest application for hydrogen today.
While a fuel cell electric vehicle might only need about 0.4 kg of hydrogen per day for typical family use, a world-scale ammonia plant needs a million times more, from 200 to 600 tons of hydrogen per day.
Modeling of a small-scale (10 kg H2 day−1) hydrogen plant suggested an overall energy efficiency of >87%. The researchers suggested that future declining electricity prices could make PMRs a competitive alternative for industrial-scale hydrogen plants integrating CO2 capture. CoorsTek Membrane Sciences research suggests that the ceramic membranes can be a competitive technology for hydrogen production with integrated carbon capture, even at a scale required for cost-effective ammonia production.
By combining an endothermic chemical reaction with an electrically operated gas separation membrane, we can create energy conversions with near zero energy loss. When you have the technology to convert energy from one form to another with almost no loss of energy, this opens up new ways to think about energy systems. For example, we can use the ceramic membrane technology to produce hydrogen from water. This will require more electric power than reforming of methane, but if electricity is available from renewable sources we can make hydrogen without CO2 emissions.
You can also think one step further and design energy systems that are not only low carbon or zero carbon, but even have negative carbon emissions. This will be the case if you use renewable electricity to reform biogas to hydrogen, and store the produced carbon from the biogas underground. In this way, hydrogen can one day become a negative emission energy carrier.—Dr. Jose Serra, Professor with Instituto de Tecnología Química (ITQ) and a co-author
Harald Malerød-Fjeld, Daniel Clark, Irene Yuste-Tirados, Raquel Zanón, David Catalán-Martinez, Dustin Beeaff, Selene H. Morejudo, Per K. Vestre, Truls Norby, Reidar Haugsrud, José M. Serra & Christian Kjølseth (2017) “Thermo-electrochemical production of compressed hydrogen from methane with near-zero energy loss” Nature Energy doi: 10.1038/s41560-017-0029-4