Seeking effective approaches for the efficient utilization of CO₂ emission is desperately interested in the development of a sustainable community. Converting CO₂ into highly valuable synthetic chemicals would be a promising way for energy storage. Using solid oxide electrolysis cells (SOECs) driven by renewable energy is expected to be one of the most efficient ways to convert electricity and industrial waste heat into chemical energy. Considering efficient energy conversion, recent development has focused on the simultaneous electrolysis of both CO₂ and H₂O in SOECs to directly produce industrially useful hydrocarbon feedstocks (e.g. H₂/CO “syngas” mixtures) and fuels by means of well-established Fischer–Tropsch (F–T)-based processes in the chemical industry so that a “Power-to-Syngas” concept can be fulfilled. For practical application, developing a highly active fuel electrode with sufficient electrolysis current density and low degradation rate is an essential task for CO₂/H₂O co-electrolysis. In addition, to achieve the direct synthesis of useful fuels, controlling CO/H₂ syngas product ratios from the feed gas of CO₂/H₂O is essential. However, the key challenge is particularly the significant effect of water gas shift reaction (WGSR) at relatively low temperatures (< 800^oC).

In previous studies, we have discovered several potential fuel-electrode candidates, such as La(Sr)Fe(Mn)O₃^[1] perovskite and CuFe₂O₄^[2] spinel for high-temperature CO₂/H₂O co-electrolysis. To facilitate their accessibility in intermediate temperatures; that is, particularly to suppress the influence of WGSR, their electrolysis performance with sufficient electrolysis current and appropriate syngas control is required to be further improved. Through an intuitive technique, infiltration of binary metal oxide,^[3] fabricating active nanocatalysts over electrode matrix has shown intensively growing interest in designing highly efficient fuel electrodes for the application of CO₂ and H₂O electrolysis.

In this study, we investigated the influence of electrolysis performance by introducing various selected functional binary oxide catalysts such as lanthanide and transition metal oxides into the scaffold of the potential La(Sr)Mn(Fe)O₃ and CuFe₂O₄ fuel electrodes by the infiltration technique for intermediate-temperature CO₂/H₂O co-electrolysis. We found that by the single- and multiple-infiltration of the selective oxides on these potential electrodes, significantly enhanced electrolysis current density and syngas product control can be achieved. For example, one of the particularly promising results shows a superior electrolysis current density (~2 A/cm² at 800^oC) can be achieved by Ce-infiltration, accompanying with markedly decreased internal resistances of the cells and exceptional Faradaic efficiency (nearly 100 %). The cell performance can also be tuned by the adjustments of infiltration concentrations and selecting multiple infiltrations of different binary metal oxides. In addition, syngas control can be significantly improved through varying oxide infiltrations and feed flow rates to increase CO₂ conversion, resulting in a considerable suppression of water gas-shift reaction, and facilitating the operation in the intermediate-temperature range.