Yihang Li

A nanostructured ceramic fuel electrode for efficient CO2/H2O electrolysis without safe gas

There is increasing interest in converting CO2/H2O to syngas via solid oxide electrolysis cells (SOECs) driven by renewable and nuclear energies. The electrolysis reaction is usually conducted through Ni–YSZ (yttria stabilized zirconia) cermets, state-of-the-art fuel electrodes for SOECs. However, one obvious problem for practical applications is the usage of CO/H2 safe gas, which must be supplied to maintain the electrode performance. This work reports a safe gas free ceramic electrode for efficient CO2/H2O electrolysis. The electrode has a heterogeneously porous structure with Sr2Fe1.5Mo0.5O6−δ (SFM) electrocatalyst nanoparticles deposited onto the inner surface of the YSZ scaffold fabricated by a modified phase-inversion tape-casting method. The nanostructured SFM–YSZ electrodes have demonstrated excellent performance for CO2–H2O electrolysis. For example, the electrode polarization resistance is 0.25 Ω cm2 under open circuit conditions while the current density is 1.1 A cm−2 at 1.5 V for dry CO2 electrolysis at 800 °C. The performance is comparable with those reported for the Ni–YSZ fuel electrodes, where safe gas must be supplied. In addition, the performance is up to one order of magnitude better than those reported for other ceramic electrodes such as La0.75Sr0.25Cr0.5Mn0.5O3−δ and La0.2Sr0.8TiO3+δ. Furthermore, the electrode exhibits good stability in the short-term test at 1.3 V for CO2-20 vol% H2O co-electrolysis, which produces a syngas with a H2/CO ratio close to 2. The reduced interfacial polarization resistance, high current density, and good stability show that the nanostructured SFM–YSZ fuel electrode is highly effective for CO2/H2O electrolysis without using the safe gas, which is critical for practical applications.

A novel fuel electrode enabling direct CO2 electrolysis with excellent and stable cell performance

Solid oxide electrolysis cells (SOECs) can directly convert CO2 to CO and O2 that are important building blocks for chemical production and other applications. However, the use of SOECs for direct CO2 electrolysis has been hampered mainly due to the absence of a stable, highly catalytically active and cost effective cathode (fuel electrode) material. Here we report a ceramic SOEC cathode material of perovskite-structured Sr1.9Fe1.5Mo0.4Ni0.1O6−δ for direct CO2 electrolysis. By annealing at 800 °C in H2, homogeneously dispersed nano-sized NiFe alloy nanoparticles are exsolved from the Sr1.9Fe1.5Mo0.4Ni0.1O6−δ perovskite lattice. The exsolved NiFe nanoparticles significantly enhance the chemical adsorption and surface reaction kinetics of CO2 with the cathode. SOECs with the novel cathode have demonstrated a peak current density of 2.16 A cm−2 under an applied voltage of 1.5 V at 800 °C and have demonstrated stable direct CO2 electrolysis performance during 500 h of operation under current density above 1 A cm−2 at 800 °C.

Highly efficient electrolysis of pure CO2 with symmetrical nanostructured perovskite electrodes

A novel symmetrical cell was prepared by facile tape-casting and infiltration methods. The cell is ideal for CO2 electrolysis, achieving a current density of 1.24 A cm−2, which could be attributed to the significantly extended active sites resulting from novel architectures with infiltrated Sr2FeMoO6 (SFM) nano-networks. The combined strategy appears to be a promising approach to produce unique architectures for CO2 electrolysis with solid oxide electrolysis cells (SOECs).