Kun Zheng

Electrochemical co-electrolysis of CO2 and H2O in solid oxide electrolysis cells (SOECs) provides a promising pathway toward carbon-neutral fuel production and renewable energy storage, yet its efficiency and selectivity remain constrained by the limited reactivity of conventional cathodes. Here, we develop a CeO2/Ni-YSZ interfacial engineering strategy for regulating the reaction behavior of Ni-YSZ electrodes during high-temperature CO2/H2O co-electrolysis. A conformal CeO2 interfacial layer introduced through a scalable impregnation method enables the tubular Ni-YSZ-supported SOEC to achieve a current density of 1.1 A·cm–2 with a Faradaic efficiency of 99.7% and stable operation over 100 h. Beyond the performance enhancement associated with CeO2 incorporation, spectroscopic analyses reveal that CeO2 modification induces interfacial electronic redistribution involving Ce and Ni species and modifies the local oxygen environment, with the CeO2 surface exhibiting a more oxygen-deficient state. Combined with density functional theory calculations, these results further indicate that oxygen-deficient CeO2 provides favorable sites for CO2 adsorption and activation. The enhanced CO2 adsorption and activation facilitate the chemical conversion of CO2 toward CO through an RWGS-mediated pathway involving hydrogen-containing intermediates generated from electrochemical H2O reduction, thereby contributing to the improved overall co-electrolysis performance. This work highlights the role of interfacial regulation in promoting CO formation and overall co-electrolysis performance, with broader implications for the development of efficient high-temperature electrochemical energy conversion technologies.

Lithium metal batteries (LMBs) are regarded as promising candidates for next‐generation high‐energy‐density storage systems. However, their practical application is severely hindered by rapid performance degradation under high‐voltage and lean‐electrolyte conditions. Constructing an anion‐enriched solvation structure to generate an inorganic‐rich solid electrolyte interphase (SEI) is critical for ensuring the stable operation of lithium metal batteries. Herein, a novel anion‐enrichment strategy is proposed by introducing a rigid cationic species (F‐TEDA ⁺ ) as a molecular anchoring additive to design a solvent‐anchored electrolyte (SAE). F‐TEDA ⁺ anchors solvent molecules via strong ion–dipole interactions, enabling the formation of an anion‐enriched solvation structure comparable to that of high‐concentration electrolytes, even at an ultralow additive dosage and conventional salt concentration. Notably, the rigid molecular framework of F‐TEDA ⁺ endows it with excellent electrochemical stability, allowing persistent regulation of the solvation structure during long‐term cycling. As a result, a 14.2 Ah Li‖Ni95 pouch cell reaches 615.3 Wh kg ⁻¹ and retains 91.4% capacity after 70 cycles at 4.5 V. This work proposes a nonconsumable solvation regulation strategy, providing a new avenue for the development of high‐voltage, high‐energy‐density lithium metal batteries.

In situ exsolution has emerged as a powerful strategy for constructing oxide-supported nanoparticle catalysts, in which catalytically active nanoparticles exsolve from the host lattice and remain socketed on the surface ^{1 - 2} . This unique architecture forms robust heterogeneous interfaces, enhances electron–ion transport, increases triple-phase boundary density, and effectively suppresses nanoparticle agglomeration ³ . However, for Sr-containing perovskite cathodes operated under the high-temperature conditions of solid oxide electrolysis cells (SOECs), severe A-site Sr segregation (e.g., SrO or SrCO₃ formation) remains a critical challenge, leading to degraded catalytic activity, increased interfacial impedance, and poor long-term stability ^{4 - 8} . Herein, we report the rational design of GDC@ (La_0.5Sr_0.5)_1-α(FeM)_1-x(CoNiCuPd)_xO_3-δ core–shell nanofibrous cathodes (M = selected metals, such as Ti, Cr, Mo) to simultaneously address activity limitations and Sr segregation in SOEC cathodes for efficient CO₂/H₂O co-electrolysis toward syngas production. The cathodes are fabricated via advanced electrospinning, yielding a three-dimensionally interconnected, high-porosity nanofibrous network with continuous charge transport pathways. The GDC shell serves as an efficient diffusion barrier, significantly extending the diffusion pathway of Sr²⁺ from the bulk phase to the electrode–gas interface, thereby suppressing Sr surface enrichment ^{9 - 10} . Under reducing conditions, multi-element nanoparticles are in situ exsolved at the perovskite-GDC interface, forming low-dimensional GDC-nanoparticles heterostructures. The lattice mismatch between the GDC shell and the in situ exsolved phase stabilizes the exsolved nanoparticles, induces additional oxygen vacancies, and promotes fast ionic transport. Notably, the composite functions as an effective “Sr trap,” capturing otherwise detrimental Sr species through oxygen-vacancy-mediated incorporation ^{11 - 12} . The incorporated Sr²⁺ further modulates the electronic structure of materials, lowers the energy barrier for CO₂ dissociation, and enhances adsorption–catalysis synergy ^{13 - 15} . Highly dispersed Pd nanoparticles are in-situ exsolved from the perovskite lattice to act as catalytically active sites under a reducing atmosphere. Simultaneously, the strong metal-carrier interactions between the Pd nanoparticles and the parent perovskite facilitate the catalyst’s oxygen exchange kinetics, synergistically boosting the overall electrochemical performance of the electrode ^{16 - 17} . Comprehensive theoretical and experimental investigations establish clear correlations among chemical composition, crystal structure, nanofiber morphology, thermal expansion behavior, oxygen nonstoichiometry, mixed ionic–electronic transport properties, and electrochemical performance. The optimized nanofibrous cathodes exhibit enhanced electrolysis activity, diminished polarization impedance, and superior long-term stability, thus providing a promising design paradigm for high-performance, robust SOEC cathodes.

A compatible CF-GPE strategy is developed for dual battery systems. It suppresses redox mediator shuttling in Li–O ₂ batteries and inhibits lithium dendrites in Li-ion batteries, enabling stable cycling and enhanced electrochemical performance.

Symmetrical solid oxide fuel cells (S-SOFCs) have gained increasing popularity in recent years due to the essential role they can play in energy systems, especially with respect to renewable energy sources. As renewable energy capacity expands globally each year, a trend expected to accelerate the intermittent nature of its electricity production is driving a growing demand for effective energy storage, however current storage technologies are not fully equipped to address this issue [1]. S-SOFCs can serve as a key element in modern energy systems by converting surplus electricity into hydrogen or ammonia in electrolysis when power supply exceeds demand. Later, this stored fuels can be used to generate electricity in fuel cell mode whenever consumption spikes. However, high operating temperatures (>800 °C) pose significant challenges for the commercialization of SOFCs, including, for instance, accelerated cell degradation and thermal stresses [2]. Efforts to reduce the operating temperature to around 700 °C or lower using well-known materials are impeded by the drastic drop in electrode electrochemical performance. Therefore, engineering electrodes that maintain strong electrocatalytic activity under lower-temperature conditions is critical for further developing affordable, high-performance S-SOFCs. In response, there is a growing focus on manufacturing heterostructured electrodes through methods such as mechanical milling, infiltration, in situ assembling, and in situ exsolution of nanoparticles. The key advantage of heterostructured electrodes lies in their capacity for high mixed ionic-electronic conductivity (MIEC) along with enhanced catalytic performance [3-4]. In this work, A-site deficient Ln _1.8-x Sr _x Fe _1.4 Ti _0.2 M _0.2 Ni _0.1 Co _0.1 O _6-δ (Ln = Sm, Pr; M = Mo, W, Cr, Mn) perovskites were systematically investigated as new electrode materials for symmetrical SOFCs. In addition, the proposed symmetrical electrode materials present also excellent performance as oxygen electrodes, such as Sr _1.8 Fe _1.4 Ti _0.2 M _0.2 Ni _0.1 Co _0.1 O _6-δ cathode with R _p of 0.11 Ω·cm² at 700 °C. It has been found that introducing A-site deficiency almost invariably reduces the polarization resistance (R _P ) during cathodic operation. For instance, A-site non-stoichiometric Sr _1.8 Fe _1.4 Ti _0.2 Cr _0.2 Ni _0.1 Co _0.1 O _6-δ (R _p = 0.072 Ω·cm² at 800°C) shows much lower electrode polarization than the stoichiometric sample (R _p = 0.16 Ω·cm² at 800°C). Moreover, the A-site deficiency and the phase transition from perovskite to Ruddlesden-Popper structure in reducing conditions significantly promote the in situ exsolution of nanoparticles, contributing to the enhanced electrochemical performance of fuel electrodes. Figure 1b illustrates the Sr ₂ Fe _1.4 Ti _0.2 Mn _0.2 Ni _0.1 Co _0.1 O _6-δ material with in situ exsolved nanoparticles on its surface after a reduction in pure hydrogen. The morphology of electrodes was further optimized by fabricating nanofibers using the electrospinning technique (Fig. 1c), leading to a significant improvement of performance at intermediate temperature range (≤700 °C). References: [1] IEA (2024), Renewables 2024, IEA, Paris, https://www.iea.org/reports/renewables-2024, Licence: CC BY 4.0. [2] S. Zarabi Golkhatmi, M.I. Asghar, P.D. Lund, A review on solid oxide fuel cell durability: Latest progress, mechanisms, and study tools, Renewable and Sustainable Energy Reviews 161 (2022) 112339. https://doi.org/https://doi.org/10.1016/j.rser.2022.112339. [3] K. Kousi, C. Tang, I.S. Metcalfe, D. Neagu, Emergence and Future of Exsolved Materials, Small 17 (2021) 2006479. https://doi.org/https://doi.org/10.1002/smll.202006479. [4] Z. Gao, L. V Mogni, E.C. Miller, J.G. Railsback, S.A. Barnett, A perspective on low-temperature solid oxide fuel cells, Energy Environ Sci 9 (2016) 1602–1644. https://doi.org/10.1039/C5EE03858H. Acknowledgements: The work is funded by the National Science Centre Poland (NCN) based on the decision number UMO-2021/43/D/ST5/00824. Michał Gogacz also acknowledges the financial support of research project supported by the program „Excellence Initiative – Research University” for the AGH University of Krakow. Figure 1

Keywords: in situ exsolution, nanocatalysts, nanofibers, electron microscopy, solid oxide cells In energy conversion and storage technologies, such as Solid Oxide Cells (SOCs), stable and catalytically active materials are highly needed to reduce the operating temperature and ensure long service life. Nanofibrous materials may provide an effective solution to these requirements. Nanofibers are regarded as promising electrode materials, providing continuous porosity that enhances the transport of reactants to the electrode, along with a high specific surface area [1–2]. Improved catalytic activity and stability can be achieved by in situ exsolution process. In situ exsolution is a segregation of selected metals to the surface and forming metallic nanoparticles. This process involves diffusion, reduction, nucleation, and growth, and is driven primarily by oxygen vacancy formation. Oxygen vacancies not only drive exsolution but also increase ionic conductivity by creating fast oxygen-ion diffusion paths. Exsolved nanoparticles anchored in the parent oxide show improved thermal stability and high resistance against sintering due to strong metal-support interaction. Compared to conventional wet impregnation methods, exsolution offers better nanoparticle distribution, size control, and durability. Reversible exsolution, where nanoparticles can be dissolved and exsolved depending on redox conditions can provide additional benefits. Reversibility of the process may mitigate agglomeration and carbon deposition when SOCs are powered by cheaper and more available hydrocarbons. Therefore, nanofiber electrodes with in situ exsolved nanoparticles are considered highly beneficial for the application in SOC electrodes [1–3]. In this work, the in situ exsolution process was comprehensively investigated by electron microscopy studies, including TEM, SEM, and EDX, along with electron and X-ray diffraction techniques. The materials were synthesized by sol-gel, and electrospinning methods. It was found that metallic nanocatalysts are exsolved in situ on the surface of the Fe-doped Ln _0.9 Ba _0.9 Mn _1.8 (Co/Ni) _0.2 O _6−δ (Ln= Nd, Sm) double perovskites. Co, Ni, and Fe are capable of being reduced to their atomic state under the operating conditions of the fuel electrode in SOCs. Microscopic analysis revealed that nanoparticles are partially anchored in the perovskite oxide (see Fig. 1a). This enhances the stability of the mixed ionic-electronic conductors and improves resistance to carbon poisoning when the fuel cell is powered by cheaper, and more available hydrocarbons. The presence of the perovskite structure was proven by the HR-TEM, with all the observed spots in the Fast Fourier Transform FTT pattern assigned to the P 4/ nmm space group. The FTT performed on the selected areas of the TEM images reveled that exsolved from perovskite nanocatalysts crystallize in Fm-3 m space group. These results are consistent with those from the XRD data. The measurements of interplanar distances in the FTT images allowed phase confirmation and determination of the crystals’ orientation. EDX mapping and point measurements confirmed that the nanocatalysts are enriched with Co, Ni, and Fe (see Fig. 1b), forming a Co–Ni–Fe alloy. During the oxidation process in air, metal nanoparticles are partially dissolved into the perovskite structure, while the remaining metals on the surface form an “empty core–shell” structure, increasing the specific surface area of the nanocatalysts. It was also found that the morphology of the material plays a key role in the in situ exsolution process. Nanofibers obtained via the electrospinning method enable the exsolution of nanocatalysts with smaller diameters (around 30 nm) and up to 20 times higher surface nanoparticle density compared to powder compounds. A reversible in situ exsolution process enables the formation of stable nanocatalysts with a reduced tendency toward sintering compared to traditional methods such as impregnation or deposition. This enhances stability, contributes to the efficient and long-term operation of Solid Oxide Cells. The favorable properties of the studied materials were confirmed in SOCs with nanofibrous electrodes decorated by in situ exsolved nanocatalysts. [1] J. Lach, M. Gogacz, P. Winiarz, Y. Ling, M. Zhou, K. Zheng, Materials 2025, 18(6), 1272 [2] J. Lach, Zheng, M. Gogacz, P. Czaja, J. Luo, A. Brzoza-Kos, ECS Transactions 2023, 111(6), 1025−1034 [3] K. Zheng, J. Lach, P. Czaja, M. Gogacz, P. Czach, A. Brzoza-Kos, P. Winiarz, J. Luo, J. Power Sources 2023, 587, 233707 The work is funded by the National Science Centre Poland (NCN) based on the decision number UMO-2021/43/D/ST5/00824. Jakub Lach acknowledge the financial support of research project supported by the program „Excellence Initiative – Research University” for the AGH University of Krakow. HRTEM, EDS and SAED results were a part of CERIC-ERIC grant no. 20232033 and were conducted in National Institute of Materials Physics, Măgurele in Romania. Figure 1