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1. A New Type of Li‐Rich Rock‐Salt Oxide Li 2 Ni 1/3 Ru 2/3 O 3 with Reversible Anionic Redox Chemistry

   https://doi.org/10.1002/adma.201807825  

   Li, Xiang ; Qiao, Yu ; Guo, Shaohua ; Jiang, Kezhu ; Ishida, Masayoshi ; Zhou, Haoshen ( January 2019 , Advanced Materials)

   Li‐rich oxide cathodes are of prime importance for the development of high‐energy lithium‐ion batteries (LIBs). Li‐rich layered oxides, however, always undergo irreversible structural evolution, leading to inevitable capacity and voltage decay during cycling. Meanwhile, Li‐rich cation‐disordered rock‐salt oxides usually exhibit sluggish kinetics and inferior cycling stability, despite their firm structure and stable voltage output. Herein, a new Li‐rich rock‐salt oxide Li₂Ni_1/3Ru_2/3O₃withFd‐3mspace group, where partial cation‐ordering arrangement exists in cationic sites, is reported. Results demonstrate that a cathode fabricated from Li₂Ni_1/3Ru_2/3O₃delivers a large capacity, outstanding rate capability as well as good cycling performance with negligible voltage decay, in contrast to the common cations disordered oxides with space groupFm‐3m. First principle calculations also indicate that rock‐salt oxide with space groupFd‐3mpossesses oxygen activity potential at the state of delithiation, and good kinetics with more 0‐TM (TM = transition metals) percolation networks. In situ Raman results confirm the reversible anionic redox chemistry, confirming O²⁻/O⁻evolution during cycles in Li‐rich rock‐salt cathode for the first time. These findings open up the opportunity to design high‐performance oxide cathodes and promote the development of high‐energy LIBs.

    

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2. Modified Ceria for “Low‐Temperature” CO 2 Utilization: A Chemical Looping Route to Exploit Industrial Waste Heat

   https://doi.org/10.1002/aenm.201901963  

   Haribal, Vasudev Pralhad ; Wang, Xijun ; Dudek, Ryan ; Paulus, Courtney ; Turk, Brian ; Gupta, Raghubir ; Li, Fanxing ( September 2019 , Advanced Energy Materials)

   Efficient CO₂utilization is key to limit global climate change. Carbon monoxide, which is a crucial feedstock for chemical synthesis, can be produced by splitting CO₂. However, existing thermochemical routes are energy intensive requiring high operating temperatures. A hybrid redox process (HRP) involving CO₂‐to‐CO conversion using a lattice oxygen‐deprived redox catalyst at relatively low temperatures (<700 °C) is reported. The lattice oxygen of the redox catalyst, restored during CO₂‐splitting, is subsequently used to convert methane to syngas. Operated at temperatures significantly lower than a number of industrial waste heat sources, this cyclic redox process allows for efficient waste heat‐utilization to convert CO₂. To enable the low temperature operation, lanthanum modified ceria (1:1 Ce:La) promoted by rhodium (0.5 wt%) is reported as an effective redox catalyst. Near‐complete CO₂conversion with a syngas yield of up to 83% at low temperatures is achieved using Rh‐promoted LaCeO_4−x. While La improves low‐temperature bulk redox properties of ceria, Rh considerably enhances the surface catalytic properties for methane activation. Density functional theory calculations further illustrate the underlying functions of La‐substitution. The highly effective redox catalyst and HRP scheme provide a potentially attractive route for chemical production using CO₂, industrial waste heat, and methane, with appreciably lowered CO₂emissions.

    

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3. Lithium carbonate-promoted mixed rare earth oxides as a generalized strategy for oxidative coupling of methane with exceptional yields

   https://doi.org/10.1038/s41467-023-43682-5  

   Zhao, Kun ; Gao, Yunfei ; Wang, Xijun ; Lis, Bar Mosevitzky ; Liu, Junchen ; Jin, Baitang ; Smith, Jacob ; Huang, Chuande ; Gao, Wenpei ; Wang, Xiaodong ; et al ( November 2023 , Nature Communications)

   The oxidative coupling of methane to higher hydrocarbons offers a promising autothermal approach for direct methane conversion, but its progress has been hindered by yield limitations, high temperature requirements, and performance penalties at practical methane partial pressures (~1 atm). In this study, we report a class of Li₂CO₃-coated mixed rare earth oxides as highly effective redox catalysts for oxidative coupling of methane under a chemical looping scheme. This catalyst achieves a single-pass C₂₊yield up to 30.6%, demonstrating stable performance at 700 °C and methane partial pressures up to 1.4 atm. In-situ characterizations and quantum chemistry calculations provide insights into the distinct roles of the mixed oxide core and Li₂CO₃shell, as well as the interplay between the Pr oxidation state and active peroxide formation upon Li₂CO₃coating. Furthermore, we establish a generalized correlation between Pr⁴⁺content in the mixed lanthanide oxide and hydrocarbons yield, offering a valuable optimization strategy for this class of oxidative coupling of methane redox catalysts.

    

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4. Chemical Stability of BaMg 0.33 Nb 0.67-X Fe x O 3-δ in High Temperature Methane Conversion Environments

   https://doi.org/10.1149/11106.0587ecst  

   Denoyer, Luke H ; Benavidez, Angelica ; Brearley, Adrian ; Ramaiyan, Kannan ; Garzon, Fernando H. ( May 2023 , ECS Transactions)

   Doped perovskite metal oxide catalysts of the form A(B_xM_1-x)O_3-δhave been instrumental in the development of solid oxide electrolyzers/fuel cells. In addition, this material class has also been demonstrated to be effective as a heterogeneous catalyst. Co-doped barium niobate perovskites have shown remarkable stability in highly acidic CO₂sensing measurements/environments (1). However, the reason for their chemical stability is not well understood. Doping with transition metal cations for B site cations often leads to exsolution under reducing conditions. Many perovskites used for the oxidative coupling of methane (OCM) or the electrochemical oxidative coupling of methane (E-OCM) either lack long term stability, or catalytic activity within these highly reducing methane environments. The Mg and Fe co-doped barium niobate BaMg_0.33Nb_0.67-xFe_xO_3-δshown activity in E-OCM reactors over long periods (2) (>100 hrs) with no iron metal exsolution observed by diffraction or STEM EDX measurements. In contrast, iron decorated BaMg_0.33Nb_0.67O₃showed little C2 conversion activity.

    

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5. Modifying La 0.6 Sr 0.4 MnO 3 Perovskites with Cr Incorporation for Fast Isothermal CO 2 ‐Splitting Kinetics in Solar‐Driven Thermochemical Cycles

   https://doi.org/10.1002/aenm.201803886  

   Carrillo, Alfonso J. ; Bork, Alexander H. ; Moser, Thierry ; Sediva, Eva ; Hood, Zachary D. ; Rupp, Jennifer L. M. ( June 2019 , Advanced Energy Materials)

   Perovskites are promising oxygen carriers for solar‐driven thermochemical fuel production due to higher oxygen exchange capacity. Despite their higher fuel yield capacity, La_0.6Sr_0.4MnO₃perovskite materials present slow CO₂‐splitting kinetics compared with state‐of‐the‐art CeO₂. In order to improve the CO production rates, the incorporation of Cr in La_0.6Sr_0.4MnO₃is explored based on thermodynamic calculations that suggest an enhanced driving force toward CO₂splitting at high temperatures for La_0.6Sr_0.4Cr_xMn_1−xO₃perovskites. Here, reported is a threefold faster CO fuel production for La_0.6Sr_0.4Cr_0.85Mn_0.15O₃compared to conventional La_0.6Sr_0.4MnO₃, and twofold faster than CeO₂under isothermal redox cycling at 1400 °C, and high stability upon long‐term cycling without any evidence of microstructural degradation. The findings suggest that with the proper design in terms of transition metal ion doping, it is possible to adjust perovskite compositions and reactor conditions for improved solar‐to‐fuel thermochemical production under nonconventional solar‐driven thermochemical cycling schemes such as the here presented near isothermal operation.

    

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