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1. Is surface modification effective to stabilize high-voltage cycling for layered P2-Na _2/3 Ni _1/3 Mn _2/3 O ₂ cathodes?

   https://doi.org/10.1039/D4CC02819H  

   Niu, Fangzhou; Qiao, Linna; Huang, Heran; Odero, Elninoh A; Zhou, Guangwen; Liu, Hao (October 2024, Chemical Communications)

   Surface coating of Na_2/3Ni_1/2Mn_2/3O₂particles suppresses high-voltage polarization but not capacity fade, which is dominated by bulk structure degradation. 

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2. Atomic doping to enhance the p-type behavior of BiFeO ₃ photoelectrodes for solar H ₂ O ₂ production

   https://doi.org/10.1039/d4ta03191a  

   Seo, Daye; Grieder, Andrew; Radmilovic, Andjela; Alamudun, Sophya F; Yuan, Xin; Ping, Yuan; Choi, Kyoung-Shin (August 2024, Journal of Materials Chemistry A)

   Na-doped BiFeO₃demonstrates an enhanced p-type behavior compared to p-type BiFeO₃prepared without extrinsic dopants, and Na-doped BiFeO₃can serve as a photocathode for solar O₂reduction to H₂O₂when coupled with Ag nanoparticle catalysts. 

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3. Electrical properties of α-Ga ₂ O ₃ films grown by halide vapor phase epitaxy on sapphire with α-Cr ₂ O ₃ buffers

   https://doi.org/10.1063/5.0090832  

   Polyakov, Alexander; Nikolaev, Vladimir; Stepanov, Sergey; Almaev, Alexei; Pechnikov, Alexei; Yakimov, Eugene; Kushnarev, Bogdan O.; Shchemerov, Ivan; Scheglov, Mikhail; Chernykh, Alexey; et al (June 2022, Journal of Applied Physics)

   We report on growth and electrical properties of α-Ga₂O₃films prepared by halide vapor phase epitaxy (HVPE) at 500 °C on α-Cr₂O₃buffers predeposited on sapphire by magnetron sputtering. The α-Cr₂O₃buffers showed a wide microcathodoluminescence (MCL) peak near 350 nm corresponding to the α-Cr₂O₃bandgap and a sharp MCL line near 700 nm due to the Cr⁺intracenter transition. Ohmic contacts to Cr₂O₃were made with both Ti/Au or Ni, producing linear current–voltage ( I– V) characteristics over a wide temperature range with an activation energy of conductivity of ∼75 meV. The sign of thermoelectric power indicated p-type conductivity of the buffers. Sn-doped, 2- μm-thick α-Ga₂O₃films prepared on this buffer by HVPE showed donor ionization energies of 0.2–0.25 eV, while undoped films were resistive with the Fermi level pinned at E_Cof 0.3 eV. The I– V and capacitance–voltage ( C– V) characteristics of Ni Schottky diodes on Sn-doped samples using a Cr₂O₃buffer indicated the presence of two face-to-face junctions, one between n-Ga₂O₃and p-Cr₂O₃, the other due to the Ni Schottky diode with n-Ga₂O₃. The spectral dependence of the photocurrent measured on the structure showed the presence of three major deep traps with optical ionization thresholds near 1.3, 2, and 2.8 eV. Photoinduced current transient spectroscopy spectra of the structures were dominated by deep traps with an ionization energy of 0.95 eV. These experiments suggest another pathway to obtain p–n heterojunctions in the α-Ga₂O₃system. 

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4. Ni ₂ P‐Modified Ta ₃ N ₅ and TaON for Photocatalytic Nitrate Reduction

   https://doi.org/10.1002/cnma.202000174  

   Wei, Lin; Adamson, Marquix_A_S; Vela, Javier (May 2020, ChemNanoMat)

   Abstract Self‐sustaining photocatalytic NO₃⁻reduction systems could become ideal NO₃⁻removal methods. Developing an efficient, highly active photocatalyst is the key to the photocatalytic reduction of NO₃⁻. In this work, we present the synthesis of Ni₂P‐modified Ta₃N₅(Ni₂P/Ta₃N₅), TaON (Ni₂P/TaON), and TiO₂(Ni₂P/TiO₂). Starting with a 2 mM (28 g/mL NO₃⁻−N) aqueous solution of NO₃⁻, as made Ni₂P/Ta₃N₅and Ni₂P/TaON display as high as 79% and 61% NO₃⁻conversion under 419 nm light within 12 h, which correspond to reaction rates per gram of 196 μmol g⁻¹ h⁻¹and 153 μmol g⁻¹ h⁻¹, respectively, and apparent quantum yields of 3–4%. Compared to 24% NO₃⁻conversion in Ni₂P/TiO₂, Ni₂P/Ta₃N₅and Ni₂P/TaON exhibit higher activities due to the visible light active semiconductor (SC) substrates Ta₃N₅and TaON. We also discuss two possible electron migration pathways in Ni₂P/semiconductor heterostructures. Our experimental results suggest one dominant electron migration pathway in these materials, namely: Photo‐generated electrons migrate from the semiconductor to co‐catalyst Ni₂P, and upshift its Fermi level. The higher Fermi level provides greater driving force and allows NO₃⁻reduction to occur on the Ni₂P surface. 

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5. Intrinsic exchange bias from interfacial reconstruction in an epitaxial Ni _x Co _y Fe _{3− x −y} O ₄ (111)/ $\alpha$ -Al ₂ O ₃ (0001) thin film family

   https://doi.org/10.1088/1361-648X/ad789d  

   Yang, Detian; Liu, Yaohua; Xu, Xiaoshan (September 2024, Journal of Physics: Condensed Matter)

   Abstract Intrinsic exchange bias is known as the unidirectional exchange anisotropy that emerges in a nominally single-component ferro-(ferri-)magnetic system. In this work, with magnetic and structural characterizations, we demonstrate that intrinsic exchange bias is a general phenomenon in (Ni, Co, Fe)-based spinel oxide films deposited on $\alpha$-Al₂O₃(0001) substrates, due to the emergence of a rock-salt interfacial layer consisting of antiferromagnetic CoO from interfacial reconstruction. We show that in Ni_xCo_yFe_3−x−yO₄(111)/ $\alpha$-Al₂O₃(0001) films, intrinsic exchange bias and interfacial reconstruction have consistent dependences on Co concentrationy, while the Ni and Fe concentration appears to be less important. This work establishes a family of intrinsic exchange bias materials with great tunability by stoichiometry and highlights the strategy of interface engineering in controlling material functionalities. 

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