Solid oxide electrolysis cell (SOEC) as an electrochemical energy conversion device has attracted increasing attention due to its large current density, high Faradaic efficiency and energy efficiency. Oxygen evolution reaction at the anode, a four-electron transfer process, is an important half-reaction for SOEC, which contributes to the main polarization resistance and consumes most electric energy during the electrolysis process. Hence, designing anode materials with high activity and stability is crucial for the performance improvement and practical application of SOEC. Recently, some advances have been made in the development of high-performance anode. In the current review, the mechanisms for CO₂ and/or H₂O electrolysis are highlighted. The physicochemical and electrochemical properties of different types of anodes are summarized. Various efficient strategies for anode optimization are introduced. Furthermore, the outlook for the future research of SOEC is included. This review might be helpful for the development of anode materials and the practical application of SOEC.

The development of inexpensive metal-nitrogen-carbon (M-N-C) catalysts for electrochemical CO₂ reduction reaction (CO₂RR) on an industrial scale has come to a standstill. Although the number of related studies and reviews has grown fast, the complexity of the M-N-C composite has limited researchers to focus on only a few variables and carry out sluggish trial-and-error optimizations in their studies. As a result, the conclusions are drawn only by artificial analysis based on a few orthogonal experimental results. To obtain more general design strategies, we have innovatively introduced machine learning (ML) into this field to address this bottleneck. A standard workflow that comprehensively utilizes different ML algorithms and black-box interpretation methods is proposed for this purpose. Besides predicting CO₂RR performance metrics for M-N-C catalysts, such as maximum faradaic efficiency with great accuracy, the ML models have also indicated simple and clear design strategies that would guide future exploration from a data science perspective. Besides, we have also demonstrated the potential of the models in guiding the development of new material systems. We thereby believe that the new research paradigm proposed may accelerate the development of this field soon.

Solid oxide electrolysis cell (SOEC) is a promising technology for CO₂ conversion and renewable energy storage with high efficiency. It is highly desirable to develop catalytically active cathodes for CO₂ electrolysis. Herein, cathode materials with different structural stabilities are designed by Nb substitution on La_0.5Sr_0.5Fe_0.8Co_0.2O_3-δ (LSFC82) to obtain La_0.5Sr_0.5Fe_0.7Co_0.2Nb_0.1O_3-δ (LSFCN721) and La_0.5Sr_0.5Fe_0.8Co_0.1Nb_0.1O_3-δ (LSFCN811), respectively. LSFC82-Sm_0.2Ce_0.8O_2-δ (SDC) cathode with inferior structural stability (ability to maintain the structure) shows desirable CO₂ electrolysis performance with the generated current density of 1.80 A cm⁻² at 1.6 V and stable performance during 110 h operation at 1.2 V and 800 °C. However, LSFC82 particles are collapsed into pieces after stability test with the generation of Co nanoparticles simultaneously. The frameworks of LSFCN721 and LSFCN811 particles maintain well because of the high-valent niobium, but Co exsolution, oxygen vacancy content and the corresponding CO₂ electrolysis performance are restricted. This work confirms that Co nanoparticles can be exsolved from LSFC82-SDC cathode during CO₂ electrolysis, providing references for constructing metallic nanoparticles decorated-perovskite cathodes for SOECs.

Active-phase engineering is regularly utilized to tune the selectivity of metal nanoparticles (NPs) in heterogeneous catalysis. However, the lack of understanding of the active phase in electrocatalysis has hampered the development of efficient catalysts for CO₂ electroreduction. Herein, we report the systematic engineering of active phases of Pd NPs, which are exploited to select reaction pathways for CO₂ electroreduction. In situ X-ray absorption spectroscopy, in situ attenuated total reflection-infrared spectroscopy, and density functional theory calculations suggest that the formation of a hydrogen-adsorbed Pd surface on a mixture of the α- and β-phases of a palladium-hydride core (α+β PdH_x@PdH_x) above -0.2 V (vs. a reversible hydrogen electrode) facilitates formate production via the HCOO^* intermediate, whereas the formation of a metallic Pd surface on the β-phase Pd hydride core (β PdH_x@Pd) below -0.5 V promotes CO production via the COOH^* intermediate. The main product, which is either formate or CO, can be selectively produced with high Faradaic efficiencies (> 90%) and mass activities in the potential window of 0.05 to -0.9 V with scalable application demonstration.

A PtFe/C catalyst has been synthesized by impregnation and high-temperature reduction followed by acid-leaching. X-ray diffraction, X-ray photoelectron spectroscopy and X-ray atomic near edge spectroscopy characterization reveal that Pt₃Fe alloy formation occurs during high-temperature reduction and that unstable Fe species are dissolved into acid solution. The difference in Fe concentration from the core region to the surface and strong O-Fe bonding may drive the outward diffusion of Fe to the highly corrugated Pt-skeleton, and the resulting highly dispersed surface FeO_x is stable in acidic medium, leading to the construction of a Pt₃Fe@Pt-FeO_x architecture. The as prepared PtFe/C catalyst demonstrates a higher activity and comparable durability for the oxygen reduction reaction compared with a Pt/C catalyst, which might be due to the synergetic effect of surface and subsurface Fe species in the PtFe/C catalyst.