Protonic Ceramic Electrochemical Cell for Efficient Separation of Hydrogen

Abstract

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 H 2 -containing streams, especially at low concentrations. Herein, a novel protonic ceramic electrochemical cell is reported that can sustainably separate pure H 2 out of H 2 -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 H 2 separation rate at 0.51 V and 500 °C is 3.3 mL cm −2 min −1 out of 10% H 2 -90% N 2 , or 2.4 mL cm −2 min −1 out of 10% H 2 -90% CH 4 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.

Development of Electrode-Supported Proton Conducting Solid Oxide Cells and their Evaluation as Electrochemical Hydrogen Pumps

“…As depicted in Figure 9 d, at least three processes can be identified to occur at a certain temperature, labeled P1, P2, and P3. On the basis of NiO-BCZY reduction temperature and the evaluation of activation energies corresponding to the DRT peaks reported in ref ( 15 ), P1 is associated with the charge transfer reaction between Ni and the BCZY interface, P2 is related to the formation of nickel-H solutions (α-phase), and P3, which is slightly visible at 350 °C, is related to the hydrogen adsorption and desorption processes on the nickel surface. From an estimate of the time constant for each peak P1 at 350, 400, and 450 °C, charge transfer is determined to occur at approximately 200, 140, and 70 kHz.…”

“… Despite the simplicity of its nature, the development of such a P-SOC has been slow or limited to lab-scale prototypes (effective surface area <1 cm 2 ) 15 due to various challenges, notably including large area defect-free membrane processing, the requirement for high sintering temperatures, chemo-thermomechanical compatibility with the components, and the necessity for gastight sealing and interconnection components to upscale to a stack level. 15 , 20 − 22 Importantly, the key parameters that govern the performance of a P-SOC pump are the conductivity, thickness, and gas-tightness of the membrane, while other parameters are kept constant (e.g., temperature, partial pressure of hydrogen, etc.).…”

“…This calls for the separation of pure hydrogen from the product gases of SMR, which can be realized via a number of technologies, such as pressure swing adsorption − or through the use of a galvanic hydrogen pump employing a perovskite based protonic ceramic membrane. − For the former techniques, hydrogen permeation occurs under a high pressure gradient across a selective metal-based membrane (usually composed of palladium or its alloys with a thickness of 10–15 μm) or molecular sieves . Although an established hydrogen purification technology operates well at large scales with a high pressure gradient (5–20 bar) across the membrane, it is capital and energy intensive.…”

Recent Advances in Membrane-Based Electrochemical Hydrogen Separation: A Review

“…Although proton-conducting ceramics are still at the early stages of development, several research efforts have been made [143][144][145][146][147][148][149][150]. Overall, the process of hydrogen permeation through a dense proton conducting membrane involves several steps [122,151] where, S', BM, S" and G is the membrane surface at the inlet, the bulk membrane, the membrane surface at the outlet, and the gas, respectively.…”

“…Although proton-conducting ceramics are still at the early stages of development, several research efforts have been made [ 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 ]. Overall, the process of hydrogen permeation through a dense proton conducting membrane involves several steps [ 122 , 151 ]: H 2 gas diffusion to reaction sites on the surface of the feed side; H 2 adsorption, dissociation, and charge transfer at the membrane surface; Proton reduction and hydrogen re-association at the membrane surface where, S’ , BM , S” and G is the membrane surface at the inlet, the bulk membrane, the membrane surface at the outlet, and the gas, respectively.…”