Libin Lei

The co-electrolysis of CO2–H2O to methane via a novel micro-tubular electrochemical reactor

Efficient and direct conversion of CO2 to hydrocarbons through electrolysis is a promising approach for energy storage and CO2 utilization. In this study, high temperature co-electrolysis of H2O–CO2 and low temperature methanation processes are synergistically integrated in a micro-tubular reactor. The temperature gradient along the micro-tubular reactor provides favorable conditions for both the electrolysis and methanation reactions. Moreover, the micro-tubular reactor can provide high volumetric factor for both the electrolysis and methanation processes. When the cathode of the micro-tubular reactor is fed with a stream of 10.7% CO2, 69.3% H2 and 20.0% H2O, an electrolysis current of −0.32 A improves CH4 yield from 12.3% to 21.1% and CO2 conversion rate from 64.9% to 87.7%, compared with the operation at open circuit voltage. Furthermore, the effects of the inlet gas composition in the cathode on the CO2 conversion rate and the CH4 yield are systematically investigated. Higher ratio of H:C in the inlet results in higher CO2 conversion rate. Among all the cases studied, the highest CH4 yield of 23.1% has been achieved when the inlet gas in the cathode is consisted of 21.3% CO2, 58.7% H2 and 20.0% H2O with an electrolysis current of −0.32 A.

Intermediate-temperature solid oxide electrolysis cells with thin proton-conducting electrolyte and a robust air electrode

A proton-conducting solid oxide electrolysis cell (H-SOEC) is a promising device that efficiently converts electrical energy to chemical energy. A H-SOEC offers a number of merits over oxygen-ion-conducting solid oxide electrolysis cells (O-SOECs). However, the development of H-SOECs is far behind that of O-SOECs, mainly due to technical challenges such as the stability of the electrolyte and electrode in a H2O-containing atmosphere under operating conditions and the fabrication of a thin electrolyte layer. In this study, BaZr0.8Y0.2O3−δ (BZY) electrolyte and a Sr2Fe1.5Mo0.5O6−δ (SFM) air electrode, both are stable in a H2O-containing atmosphere under operating conditions, are evaluated in H-SOECs. In addition, in order to improve the performance of H-SOECs, a thin BZY electrolyte layer (about 16 μm in thickness) and nano-scaled SFM–BZY air electrode are fabricated successfully, showing excellent SOEC performance (−0.21 A cm−2 at 600 °C) and achieving a faradaic efficiency of 63.6% at intermediate temperature.

Ta-Doped SrCoO3−δ as a promising bifunctional oxygen electrode for reversible solid oxide fuel cells: a focused study on stability

The present work reports a thorough investigation into the structural, thermal, electrical and electrochemical properties of 10 mol% Ta-doped SrCoO3−δ (denoted as SCT10) as a promising bifunctional oxygen electrode for intermediate-temperature reversible solid oxide fuel cells. The high-temperature X-ray diffraction (HT-XRD) and high-temperature neutron powder diffraction (HT-NPD) studies reveal that SCT10 exhibits a single primitive cubic phase at ≥200 °C. The thermogravimetric analysis (TGA) and HT-NPD show consistent results of oxygen nonstoichiometry and the oxidation-state of Co-ions as a function of temperature. More importantly, the dependency of electronic conductivity and electrochemical activity on temperature, partial pressure of oxygen and time unequivocally suggests that SCT10 is a better and more stable bifunctional oxygen electrode than its rival, 10 mol% Nb-doped SCO (SCN10), making it more attractive for practical applications.