Electrolysis of Carbon Dioxide in a Solid Oxide Electrolyzer with Silver-Gadolinium-Doped Ceria Cathode

Abstract

Splitting CO2 into CO and pure O2 at high temperature through solid oxide electrolyzers (SOEs) could provide an efficient way for energy storage and CO2 utilization. Tubular solid oxide electrolysis cells, with yttrium-stabilized-zirconia (YSZ) as electrolyte, strontium-doped lanthanate (LSM) as anode, cermet of Ag-GDC (gadolinium-doped-ceria) as cathode, is fabricated and operated as SOEs for electrolysis of pure CO2. Such an SOE shows a minimum electrolyzing voltage of 0.70 V and a current density of 1359 mA cm−2 at 2 V. Its CO production rates are 3.1, 6.6 and 10.0 mL min−1 at electrical currents of 0.5, 1.0 and 1.5 A, respectively, at 800°C. The corresponding Faraday efficiencies are 88.6%, 94.3%, and 95.2%, and the electrical energy conversion efficiencies are 75.4%, 65.2%, and 56.5%, respectively. An SOE with Ag-GDC electrode is steadily operated at 1.59 V for pure CO2 electrolysis at 800°C for 18 h, suggesting that Ag-GDC is a promising cathode material for SOEs of CO2 electrolysis.