A La1.85Mg0.15Ce2O7-δ-based ceramic hydrogen pump for stable hydrogen separation out of the H2-CO2 mixtures

• Published in: Separation and purification technology 2025-06, Vol.359, p.130466, Article 130466
• Main Authors: Dai, Mingxuan, Tong, Xinyue, Tong, Yongcheng, Zhou, Wei, Chen, Chusheng, Zhan, Zhongliang
• Format: Article
• Language: English
• Subjects: Doped La2Ce2O7 oxides; Electrochemical hydrogen pumps; Hydrogen separation; Protonic ceramic cells; Symmetrical fuel cells
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2024.130466

[Display omitted] •Ceramic hydrogen pumps with thin La1.85Mg0.15Ce2O7-δ electrolytes are proposed.•Selective hydrogen separation out of 10 % H2–90 % CO2 is demonstrated.•The H2 fluxes are largely limited by bulk transport of protons in electrolytes. Currently, hydrogen is largely produced from steam methane reforming with the H2-and CO2-containing stream as the process gas. It is highly relevant to explore new pathways to efficiently separate hydrogen out of the H2-CO2 mixed gases. In the present work, a novel ceramic hydrogen pump for H2 purification is designed with thin La1.85Mg0.15Ce2O7-δ (LMCO) electrolytes supported by symmetrical Ni-LMCO electrodes, and is fabricated by using the tape casting, tape lamination and co-sintering techniques. Chemical stability and proton conductivities are evaluated for fluorite LMCO oxides in humidified 10 % H2-90 % CO2. Superior stability of LMCO in CO2 allows for stable and selective hydrogen separation out of humidified 10 % H2–90 % CO2. The Faraday’s efficiency decreases pronouncedly with an increase in the operation temperature, e.g., ≈ 30 % at 700 ℃ vs. ≈ 76 % at 500 ℃, due to increasingly high reduction susceptibility of Ce4+ to Ce3+ and the resultant electronic conductivities. A reasonable H2 flux of 0.57 mL·min−1·cm−2 is achieved at 500 °C and 0.25 V with electricity consumption of 0.72 kWh·Nm−3 H2. Operation at a higher pumping voltage of 0.49 V yields a larger H2 flux of 1.16 mL·min−1·cm−2, but simultaneously results in higher electricity consumption of 1.42 kWh·Nm−3 H2. Impedance analysis reveals that the H2 fluxes for the present ceramic hydrogen pump are predominantly limited by high resistances against bulk transport of protons through the LMCO electrolytes as well as sluggish hydrogen oxidation kinetics in humidified 10 % H2–90 % CO2.