Reversibly in-situ anchoring copper nanocatalyst in perovskite titanate cathode for direct high-temperature steam electrolysis

• Published in: International journal of hydrogen energy 2014-04, Vol.39 (11), p.5485-5496
• Main Authors: Qi, Wentao, Ruan, Cong, Wu, Guojian, Zhang, Yong, Wang, Yan, Xie, Kui, Wu, Yucheng
• Format: Article
• Language: English
• Subjects: Alternative fuels. Production and utilization; Anchoring; Applied sciences; CATALYSTS; Cathode; Cathodes; Cathodic polarization; COMPOSITES; Copper; Electrical properties; ELECTROLYSIS; Electrolytic cells; Energy; Exact sciences and technology; Exsolution; Fuels; Hydrogen; MICROSTRUCTURES; Nanostructure; POLARIZATION; Scanning electron microscopy; STEAM; Steam electrolysis; THERMOGRAVIMETRIC ANALYSIS
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2014.01.108

This paper investigates a potential cathode material (La0.2Sr0.8)0.9Ti0.9Cu0.1O3−δ (LSTCO) with A-site deficiency and B-site excess which was designed as a parent material for anchoring exsolved copper nanocatalyst on the surface of La0.2Sr0.8TiO3+δ (LSTO) through a high-temperature reduction. Physical characterization of the samples by combined use of X-ray diffraction, scanning electron microscope, energy-dispersive spectroscopy, thermogravimetric analyzer and X-ray photoelectron spectroscopy indicated that the exsolution and dissolution of the Cu nanoparticles in the cathode was completely reversible in the redox cycles. Electrical properties of LSTO and LSTCO were systematically investigated which correlated closely with electrochemical performance of the composite electrodes in symmetrical cells and electrolysis cells. Polarization resistance (Rp) of the symmetrical cells was improved from 3 Ω cm2 of the LSTO to 1.5 Ω cm2 of the LSTCO in hydrogen atmosphere at 800 °C. Current efficiencies of the solid oxide electrolyzer with Cu-anchored LSTO cathode were found to be enhanced by approximately 20% compared to the bare cathode with or without reducing gas flowing over them under the applied voltage of 2.0 V at 800 °C, respectively. •In-situ anchoring of Cu nanocatalyst achieved through controlling non-stoichiometry.•The exsolution of Cu nanocatalyst is completely reversible in redox cycles.•The Cu catalyst significantly improves Faraday efficiency for steam electrolysis.•The composite cathode shows short-term stability for direct steam electrolysis.