Composite fuel electrode La0.2Sr0.8TiO3−δ–Ce0.8Sm0.2O2−δ for electrolysis of CO2 in an oxygen-ion conducting solid oxide electrolyser

Abstract

Composite Ni-YSZ fuel electrodes are able to operate only under strongly reducing conditions for the electrolysis of CO(2) in oxygen-ion conducting solid oxide electrolysers. In an atmosphere without a flow of reducing gas (i.e., carbon monoxide), a composite fuel electrode based on redox-reversible La(0.2)Sr(0.8)TiO(3+δ) (LSTO) provides a promising alternative. The Ti(3+) was approximately 0.3% in the oxidized LSTO (La(0.2)Sr(0.8)TiO(3.1)), whereas the Ti(3+) reached approximately 8.0% in the reduced sample (La(0.2)Sr(0.8)TiO(3.06)). The strong adsorption of atmospheric oxygen in the form of superoxide ions led to the absence of Ti(3+) either on the surface of oxidized LSTO or the reduced sample. Reduced LSTO showed typical metallic behaviour from 50 to 700 °C in wet H(2); and the electrical conductivity of LSTO reached approximately 30 S cm(-1) at 700 °C. The dependence of [Ti(3+)] concentration in LSTO on P(O(2)) was correlated to the applied potentials when the electrolysis of CO(2) was performed with the LSTO composite electrode. The electrochemical reduction of La(0.2)Sr(0.8)TiO(3+δ) was the main process but was still present up to 2 V at 700 °C during the electrolysis of CO(2); however, the electrolysis of CO(2) at the fuel electrode became dominant at high applied voltages. The current efficiency was approximately 36% for the electrolysis of CO(2) at 700 °C and a 2 V applied potential.

In situ formation of oxygen vacancy in perovskite Sr0.95Ti0.8Nb0.1M0.1O3 (M = Mn, Cr) toward efficient carbon dioxide electrolysis

“…In general, the local starvation of CO 2 primarily leads to large electrode polarizations and low current efficiencies for CO 2 electrolysis at high temperatures21. In our previous report, efficient CO 2 electrolysis was demonstrated in an oxide-ion conducting solid-oxide electrolyzer with a cathode based on La 0.2 Sr 0.8 TiO 3.1 , and promising electrode polarizations have been achieved under a series of external voltage loads22. However, mass transfer limitation, especially the insufficient adsorption of CO 2 , was observed at the cathode, and the current efficiency for the production of CO was only approximately 36%22.…”

Enhancing CO2 electrolysis through synergistic control of non-stoichiometry and doping to tune cathode surface structures

“…Perovskite-type doped strontium titanates, (La,Sr)TiO 3+δ (LST O+ ), are such materials, due to the reducibility of Ti 4+ to Ti 3+ , and have therefore attracted a significant amount of interest within the field of SOE and fuel cell electrodes1011. A composite cathode based on La 0.2 Sr 0.8 TiO 3.1 was shown to be well adapted to direct CO 2 electrolysis12, because the titanate is partially electrochemically reduced (Ti 4+ →Ti 3+ ) at potentials required for CO 2 reduction and the n-type electronic conduction is accordingly enhanced, but cathode performance for CO 2 electrolysis is still limited by insufficient electro-catalytic activity and the weak high-temperature chemical adsorption of reactants13.…”

“…This is believed to cause local starvation of CO 2 in SOE cathodes13712. Currently, preferential chemical adsorption of CO 2 on solid oxide materials is based on grafting solid amines, which produces an alkaline surface.…”

In situ Growth of NixCu1-x Alloy Nanocatalysts on Redox-reversible Rutile (Nb,Ti)O4 Towards High-Temperature Carbon Dioxide Electrolysis

“…High-temperature electrolysis based on the redox-stable LSCM or LSTO cathode has been reported for the direct electrolysis of H 2 O, CO 2 or H 2 O/CO 2 , and promising electrode performances have also been observed1314151617. However, the LSCM, as a p-type conductor, is not well adapted to strong reducing potentials.…”

“…By contrast, LSTO, which exhibits n-type conductivity upon reduction, has been considered a breakthrough in the development of redox-stable anode materials for SOFCs and has also been utilised for direct high-temperature electrolysis20. However, this material's insufficient catalytic activity still restricts the electrode polarisation and current efficiency during high-temperature electrolysis15. To improve the performance of LSTO, metal catalysts have been introduced, which has resulted in a substantially enhanced electrode performance2122.…”