More Like this

1. Studies of Functional Defects for Fast Na‐Ion Conduction in Na 3− y PS 4− x Cl x with a Combined Experimental and Computational Approach

   https://doi.org/10.1002/adfm.201807951  

   Feng, Xuyong ; Chien, Po‐Hsiu ; Zhu, Zhuoying ; Chu, Iek‐Heng ; Wang, Pengbo ; Immediato‐Scuotto, Marcello ; Arabzadeh, Hesam ; Ong, Shyue Ping ; Hu, Yan‐Yan ( January 2019 , Advanced Functional Materials)

   All‐solid‐state rechargeable sodium (Na)‐ion batteries are promising for inexpensive and high‐energy‐density large‐scale energy storage. In this contribution, new Na solid electrolytes, Na_3−yPS_4−xCl_x, are synthesized with a strategic approach, which allows maximum substitution of Cl for S (x= 0.2) without significant compromise of structural integrity or Na deficiency. A maximum conductivity of 1.96 mS cm⁻¹at 25 °C is achieved for Na_3.0PS_3.8Cl_0.2, which is two orders of magnitude higher compared with that of tetragonal Na₃PS₄(t‐Na₃PS₄). The activation energy (E_a) is determined to be 0.19 eV. Ab initio molecular dynamics simulations shed light on the merit of maximizing Cl‐doping while maintaining low Na deficiency in enhanced Na‐ion conduction. Solid‐state nuclear magnetic resonance (NMR) characterizations confirm the successful substitution of Cl for S and the resulting change of P oxidation state from 5+ to 4+, which is also verified by spin moment analysis. Ion transport pathways are determined with a tracer‐exchange NMR method. The functional detects that promote Na ‐ion transport are maximized for further improvement in ionic conductivity. Full‐cell performance is demonstrated using Na/Na_3.0PS_3.8Cl_0.2/Na₃V₂(PO₄)₃with a reversible capacity of ≈100 mAh g^‐1at room temperature.

    

   more » « less
2. Density Functional Theory Study of the Initial Stages of Cl-Induced Degradation of α-Cr 2 O 3 Passive Film

   https://doi.org/10.1149/1945-7111/abb381  

   Oware Sarfo, Kofi ; Murkute, Pratik ; Isgor, O. Burkan ; Zhang, Yongfeng ; Tucker, Julie ; Árnadóttir, Líney ( September 2020 , Journal of The Electrochemical Society)

   The ion exchange and point defect models are two prominent models describing the role of anions, such as chlorides, in the degradation of passive oxide films. Here the thermodynamic feasibility of critical steps of Cl-induced degradation of a hydroxylated α-Cr₂O₃(0001) surface, as proposed by these two models, are studied. Both models begin with Cl substitution of surface OH and H₂O, which becomes less favorable with increasing Cl coverage. The initial stages of Cl-induced breakdown of the α-Cr₂O₃depend on Cl coverage and the presence of O vacancy near the surface as follows: (1) neither Cl insertion (supporting the ion exchange model) nor Cr vacancy formation (supporting the point defect model) is feasible at low Cl coverages except in the presence of O vacancies near the surface, where Cl insertion is thermodynamically feasible even at low coverages, (2) in the absence of O vacancies, Cr vacancy formation becomes feasible from 10/12 ML onwards whereas Cl insertion by exchange with subsurface OH only becomes feasible at full coverage. This implies that at higher coverages Cl-induced degradation first initiatesthrough a vacancy formation mechanism, but both insertion and vacancy formation would be feasible at full coverage.

    

   more » « less
3. A Nonheme Mononuclear {FeNO} 7 Complex that Produces N 2 O in the Absence of an Exogenous Reductant

   https://doi.org/10.1002/ange.202109062  

   Dey, Aniruddha ; Gordon, Jesse B. ; Albert, Therese ; Sabuncu, Sinan ; Siegler, Maxime A. ; MacMillan, Samantha N. ; Lancaster, Kyle M. ; Moënne‐Loccoz, Pierre ; Goldberg, David P. ( August 2021 , Angewandte Chemie)

   A new nonheme iron(II) complex, Fe^II(Me₃TACN)((OSi^Ph2)₂O) (1), is reported. Reaction of1with NO_(g)gives a stable mononitrosyl complex Fe(NO)(Me₃TACN)((OSi^Ph2)₂O) (2), which was characterized by Mössbauer (δ=0.52 mm s⁻¹, |ΔE_Q|=0.80 mm s⁻¹), EPR (S=3/2), resonance Raman (RR) and Fe K‐edge X‐ray absorption spectroscopies. The data show that2is an {FeNO}⁷complex with anS=3/2 spin ground state. The RR spectrum (λ_exc=458 nm) of2combined with isotopic labeling (¹⁵N,¹⁸O) reveals ν(N‐O)=1680 cm⁻¹, which is highly activated, and is a nearly identical match to that seen for the reactive mononitrosyl intermediate in the nonheme iron enzyme FDPnor (ν(NO)=1681 cm⁻¹). Complex2reacts rapidly with H₂O in THF to produce the N‐N coupled product N₂O, providing the first example of a mononuclear nonheme iron complex that is capable of converting NO to N₂O in the absence of an exogenous reductant.

    

   more » « less
4. A Nonheme Mononuclear {FeNO} 7 Complex that Produces N 2 O in the Absence of an Exogenous Reductant

   https://doi.org/10.1002/anie.202109062  

   Dey, Aniruddha ; Gordon, Jesse B. ; Albert, Therese ; Sabuncu, Sinan ; Siegler, Maxime A. ; MacMillan, Samantha N. ; Lancaster, Kyle M. ; Moënne‐Loccoz, Pierre ; Goldberg, David P. ( August 2021 , Angewandte Chemie International Edition)

   A new nonheme iron(II) complex, Fe^II(Me₃TACN)((OSi^Ph2)₂O) (1), is reported. Reaction of1with NO_(g)gives a stable mononitrosyl complex Fe(NO)(Me₃TACN)((OSi^Ph2)₂O) (2), which was characterized by Mössbauer (δ=0.52 mm s⁻¹, |ΔE_Q|=0.80 mm s⁻¹), EPR (S=3/2), resonance Raman (RR) and Fe K‐edge X‐ray absorption spectroscopies. The data show that2is an {FeNO}⁷complex with anS=3/2 spin ground state. The RR spectrum (λ_exc=458 nm) of2combined with isotopic labeling (¹⁵N,¹⁸O) reveals ν(N‐O)=1680 cm⁻¹, which is highly activated, and is a nearly identical match to that seen for the reactive mononitrosyl intermediate in the nonheme iron enzyme FDPnor (ν(NO)=1681 cm⁻¹). Complex2reacts rapidly with H₂O in THF to produce the N‐N coupled product N₂O, providing the first example of a mononuclear nonheme iron complex that is capable of converting NO to N₂O in the absence of an exogenous reductant.

    

   more » « less
5. Impact of Post‐Lithography Polymer Residue on the Electrical Characteristics of MoS 2 and WSe 2 Field Effect Transistors

   https://doi.org/10.1002/admi.201801321  

   Liang, Jierui ; Xu, Ke ; Toncini, Blaec ; Bersch, Brian ; Jariwala, Bhakti ; Lin, Yu‐Chuan ; Robinson, Joshua ; Fullerton‐Shirey, Susan K. ( December 2018 , Advanced Materials Interfaces)

   The residue of common photo‐ and electron‐beam resists, such as poly(methyl methacrylate) (PMMA), is often present on the surface of 2D crystals after device fabrication. The residue degrades device properties by decreasing carrier mobility and creating unwanted doping. Here, MoS₂and WSe₂field effect transistors (FETs) with residue are cleaned by contact mode atomic force microscopy (AFM) and the impact of the residue on: 1) the intrinsic electrical properties, and 2) the effectiveness of electric double layer (EDL) gating are measured. After cleaning, AFM measurements confirm that the surface roughness decreases to its intrinsic state (i.e., ≈0.23 nm for exfoliated MoS₂and WSe₂) and Raman spectroscopy shows that the characteristic peak intensities (E_2gand A_1g) increase. PMMA residue causes p‐type doping corresponding to a charge density of ≈7 × 10¹¹cm⁻²on back‐gated MoS₂and WSe₂FETs. For FETs gated with polyethylene oxide (PEO)₇₆:CsClO₄, removing the residue increases the charge density by 4.5 × 10¹²cm⁻², and the maximum drain current by 247% (statistically significant,p< 0.05). Removing the residue likely allows the ions to be positioned closer to the channel surface, which is essential for achieving the best possible electrostatic gate control in ion‐gated devices.

    

   more » « less