Zheng, Kun
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inżynieria materiałowa
inżynieria środowiska, górnictwo i energetyka
inżynieria środowiska, górnictwo i energetyka
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Item type:Article, Access status: Open Access , Negative thermal expansion coefficient materials: from basics to applications, recent advances in solid oxide cells and future perspectives(2025) Winiarz, Piotr; Sultan, Amir; Ling, Yihan; Zheng, Kun
Wydział Energetyki i PaliwNegative thermal expansion has always interested scientists as an extraordinary physical property. Understanding this specific phenomenon allows to design and synthesize materials with abnormal, anisotropic, near-zero, or negative expansion. In effect, these materials find applications in many branches of science like mechanics, optics, micro- and nanoelectronics, magnetics, and medical and chemical applications. Since the great majority of these materials are electrical insulators, they did not find practical applications in electrochemistry. However, recently a new group of perovskite-based materials was discovered which gave vast opportunities to utilize such materials in fuel cell technology giving outstanding possibilities to improve and enhance their electrical, thermomechanical, and electrochemical properties. Therefore, the most limiting factor, which is the long-term stability, may be mitigated leading to improved electrolyte/electrode durability which enables future perspectives possibly allowing for faster commercialization of the technology. In this review article, we present a general insight into thermal expansion and its physical explanation along with many examples of materials with negative expansion, exhibiting different crystal structures. Experimental techniques for thermal expansion coefficient evaluation are summarized and widely discussed. In the main part of the article, many applications of materials with negative expansion are presented, focusing on recent advances in electrochemistry, mainly as composite electrodes with negative thermal expansion materials addition, which improves the electrochemical performance of solid oxide cells. In the summary, we present drawn conclusions and discuss future perspectives as a widely and rapidly developing branch of electrochemistry.Item type:Article, Access status: Open Access , Exploring the frontiers of electrochemical $CO_{2}$ conversion: a comprehensive review(2025) Ashraf, Shahid; Gohar, Osama; Khan, Muhammad Zubair; Tariq, Urooj; Ahmad, Jawad; Awan, Ramsha Javed; Zheng, Kun; Ur Rehman, Junaid; Abdul Karim, Muhammad Ramzan; Ishfaq, Hafiz Ahmad; Said, Zafar; Motola, Martin; Han, Ning; Hanif, Muhammad Bilal
Wydział Energetyki i PaliwThe electrochemical conversion of carbon dioxide into valuable products is pivotal for maintaining the global carbon cycle and mitigating global warming. This review explores the advancements in electrochemical $CO_{2}$ conversion, particularly focusing on producing methanol, ethanol, and n-propanol using various catalysts such as metals, metal oxides, metal alloys, and metal organic frameworks. Additionally, it covers the photoelectrochemical (PEC) conversion of $CO_{2}$ into alcohols. The primary objective is to identify efficient electrocatalysts for ethanol, methanol, and n-propanol production, prioritizing selectivity, stability, Faradaic efficiency (FE), and current density. Notable catalysts include PtxZn nanoalloys, which exhibit an FE of ∼81.4 % for methanol production, and trimetallic Pt/Pb/Zn nanoalloys, aimed at reducing Pt costs while enhancing catalyst stability and durability. Metal oxide catalysts like thin film $Cu_{2}O/CuO$ on nickel foam and $Cu_{2}O/ZnO$ achieve FE values of ∼38 % and ∼16.6 % for methanol production, respectively. Copper-based metal-organic frameworks, such as Cu@ $Cu_{2}O$, demonstrate an FE of ∼45 % for methanol production. Similarly, $Ag_{0.14}/Cu_{0.86}$ and Cu–Zn alloys exhibit FEs of ∼63 % and ∼46.6 %, respectively, for ethanol production. Notably, n-propanol production via Pd–Cu alloy and $graphene/ZnO/Cu_{2}O$ yields FEs of ∼13.7 % and ∼23 %, respectively. Furthermore, the review discusses recent advancements in PEC reactor design, photoelectrodes, reaction mechanisms, and catalyst durability. By evaluating the efficiency of these devices in liquid fuel production, the review addresses challenges and prospects in $CO_{2}$ conversion for obtaining various valuable products.Item type:Article, Access status: Open Access , Designing high-performance quasi-symmetrical solid oxide cells with a facile chemical modification strategy for Sr2Fe2-xWxO6-δ ferrites electrodes with in situ exsolution of nanoparticles(2023) Zheng, Kun; Lach, Jakub; Czaja, Paweł; Gogacz, Michał; Czach, Patryk; Brzoza-Kos, Agnieszka; Winiarz, Piotr; Luo, Jie
Wydział Energetyki i PaliwThe chemical modification of perovskites is one of the most effective design strategies for electrode materials for solid oxide cells. In this work, the tungsten doping in $Sr_{2}Fe_{2−x}W_{x}O_{6−δ}$ shows a significant impact on their physicochemical properties, and it leads to a substantial change of electrochemical properties in the air and reducing conditions, with $Sr_{2}Fe_{1.8}W_{0.2}O_{6−δ}$ (Rp = 0.06 Ω cm2 at 800 °C stable for 100 h in air) and $Sr_{2}Fe_{1.6}W_{0.4}O_{6−δ}$ (Rp = 0.56 Ω cm2 at 800 °C over 100 h in 5 vol% $H_{2}/Ar$) being the best air and fuel electrode candidates, respectively. We have proposed an attractive design of high-performance quasi-symmetrical solid oxide cells with $80%Sr_{2}Fe_{1.8}W_{0.2}O_{6−δ}+20%GDC$ | LSGM | $80%Sr_{2}Fe_{1.6}W_{0.4}O_{6−δ}+20%GDC$, demonstrating excellent power outputs ($874 mW cm^{−2}$ at 850 °C in wet $H_{2}$) and good current density of 743 mA $cm^{−2}$ at 1.5 V in electrolysis mode at 750 °C. A good performance of 451 mW $cm^{−2}$ was also recorded in wet $CH_{4}$ at 800 °C. The in situ exsolved metallic iron nanoparticles decorated on the $Sr_{2}Fe_{1.6}W_{0.4}O_{6−δ}$ anode contribute to the excellent electrochemical performance of cells. This study provides a successful scenario for designing high-performance symmetrical solid oxide cells with a facile chemical modification strategy for ferrites electrodes with in situ exsolution of nanoparticles.Item type:Article, Access status: Open Access , Tailoring the Stability of Ti-Doped Sr2Fe1.4TixMo0.6−xO6−δ Electrode Materials for Solid Oxide Fuel Cells(2022) Zheng, Kun; Albrycht, Maciej; Chen, Min; Qi, Kezhen; Czaja, Paweł
Wydział Energetyki i PaliwIn this work, the stability of $Sr_{2}(FeMo)O_{6−δ}$-type perovskites was tailored by the substitution of Mo with Ti. Redox stable $Sr_{2}Fe_{1.4}Ti_{x}Mo_{0.6−x}O_{6−δ}$ (x = 0.1, 0.2 and 0.3) perovskites were successfully obtained and evaluated as potential electrode materials for SOFCs. The crystal structure as a function of temperature, microstructure, redox stability, and thermal expansion properties in reducing and oxidizing atmospheres, oxygen content change, and transport properties in air and reducing conditions, as well as chemical stability and compatibility towards typical electrolytes have been systematically studied. All $Sr_{2}Fe_{1.4}Ti_{x}Mo_{0.6−x}O_{6−δ}$ compounds exhibit a regular crystal structure with Pm-3m space group, showing excellent stability in oxidizing and reducing conditions. The increase of Ti-doping content in materials increases the thermal expansion coefficient (TEC), oxygen content change, and electrical conductivity in air, while it decreases the conductivity in reducing condition. All three materials are stable and compatible with studied electrolytes. Interestingly, redox stable $Sr_{2}Fe_{1.4}Ti_{0.1}Mo_{0.5}O_{6−δ}$, possessing 1 μm grain size, low TEC $(15.3 \ × \ 10^{−6} \ K^{−1})$, large oxygen content change of $0.72 \ mol·mol^{−1}$ between 30 and 900 °C, satisfactory conductivity of $4.1–7.3 \ S·cm^{−1}$ in $5\% \ H_{2}$ at 600–800 °C, and good transport coefficients D and k, could be considered as a potential anode material for SOFCs, and are thus of great interest for further studies.Item type:Article, Access status: Open Access , Electrospun Nanofiber Electrodes with in situ Exsolved Nanocatalysts for Symmetrical SOCs(2023) Lach, Jakub; Zheng, Kun; Gogacz, Michał; Czaja, Paweł; Luo, Jie; Brzoza-Kos, Agnieszka
Wydział Energetyki i PaliwIn this work, A-site deficient $Sm_{0.9}Ba_{0.9}Mn_{1.8−x}Fe_{x}Co_{0.1}Ni_{0.1}O_{6−δ}$ (x = 0, 0.45 and 0.9) double perovskites with in situ exsolved nanoparticles were successfully obtained and evaluated as electrode materials for symmetrical Solid Oxide Cells (SOCs). All obtained oxides belong to the P4/nmm tetragonal system, and a phase transition from P4/nmm to P4/mmm was recorded by the HT-XRD in the air. The in situ exsolution of nanoparticles has been confirmed by the XRD and SEM analysis. The proposed materials present excellent redox stability and moderate thermal expansion coefficients. Electrospun nanofibers (with 150 nm diameter) were successfully fabricated, indicating an excellent potential application in the electrode. The results show the developed A-site deficient double perovskites with iron doping at Mn-site can be potentially applied as novel electrode materials for symmetrical SOCs.Item type:Article, Access status: Open Access , Magnesium-Doped Sr2(Fe,Mo)O6−δ Double Perovskites with Excellent Redox Stability as Stable Electrode Materials for Symmetrical Solid Oxide Fuel Cells(2022) Zheng, Kun; Lach, Jakub; Zhao, Hailei; Huang, Xiubing; Qi, Kezhen
Wydział Energetyki i PaliwIn this work, magnesium-doped $Sr_{2}Fe_{1.2}Mg_{0.2}Mo_{0.6}O_{6−δ}$ and $Sr_{2}Fe_{0.9}Mg_{0.4}Mo_{0.7}O_{6−δ}$ double perovskites with excellent redox stability have been successfully obtained. The physicochemical properties including: crystal structure properties, redox stability, thermal expansion properties in oxidizing and reducing conditions, oxygen content as a function of temperature and transport properties, as well as the chemical compatibility with typical electrolytes have been systematically investigated. The in situ oxidation of reduced samples using high-temperature XRD studies shows the crystal structure of materials stable at up to a high-temperature range. The in situ reduction and oxidation of sinters with dilatometer measurements prove the excellent redox stability of materials, with the thermal expansion coefficients measured comparable with electrolytes. The oxygen nonstoichiometry δ of compounds was determined and recorded in air and argon up to 900 °C. $Sr_{2}Fe_{1.2}Mg_{0.2}Mo_{0.6}O_{6−δ}$ oxide presents satisfactory values of electrical conductivity in air ($56.2 \ S·cm^{−1}$ at 600 °C) and reducing conditions ($10.3 \ S·cm^{−1}$ at 800 °C), relatively high coefficients D and k, and good ionic conductivity (cal. $0.005 \ S·cm^{−1}$ at 800 °C). The stability studies show that both compounds are compatible with $Ce_{0.8}Gd_{0.2}O_{1.9}$ but react with the $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.2}O_{3−d}$ electrolyte. Therefore, the magnesium-doped double perovskites with excellent redox stability can be potentially qualified as electrode materials for symmetrical SOFCs and are of great interest for further investigations.Item type:Article, Access status: Open Access , 2030 roadmap on two-dimensional materials for energy storage and conversion(2026) Ding, Lan; Qi, Kezhen; Huang, Zimo; Yu, Ying; Yang, Ze; Tabibi, Sepehr; Khataee, Alireza; Hao, Lei; Zhang, Qitao; Popkov, Vadim; Kaneva, Maria; Lobinsky, Artem; Yu, Zhipeng; Li, Jun; Sultan, Amir; Zheng, Kun; Qu, Gan; Ma, Dandan; Shi, Jian-Wen; Ismail, Ahmed
Wydział Energetyki i PaliwTwo-dimensional (2D) materials have rapidly emerged as transformative platforms for energy storage and conversion, owing to their atomic-scale thickness, tunable electronic structures, and versatile chemical functionalities. Over the past five years, remarkable advances in material synthesis, interface engineering, and device integration have unlocked new opportunities, yet challenges in stability, scalability, and performance optimization remain. In this roadmap, we provide an updated perspective toward 2030, systematically reviewing eleven representative 2D material classes, which can be broadly grouped into carbon-based materials, inorganic semiconductors, framework materials, and layered nanosheet systems. Their opportunities and challenges in electrochemical energy storage, photocatalysis, and electrocatalysis are highlighted. We believe this roadmap can enrich the development of 2D materials for sustainable energy technologies, and provide useful guidance for both fundamental studies and practical applications in the coming decade.