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17 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Irreversible anion oxidation leads to dynamic charge compensation in the Ru-poor, Li-rich cathode Li2Ru0.3Mn0.7O3 Joshua J. Zak , Mateusz Zuba , Zachary W. Lebens-Higgins , Heran Huang , Matthew J. Crafton , Nathan F. Dalleska , Bryan D. Mccloskey , Louis F. J. Piper , Kimberly A. See Acs Energy Letters DOI: 10.1021/acsenergylett.2c02537 Diamond Proposal Number(s): [127494] Show Abstract ▼ Abstract: Conventional cathodes for Li-ion batteries are layered transition-metal oxides that support Li+ intercalation charge-balanced by redox on the transition metals. Oxidation beyond one electron per transition metal can be achieved in Li-rich layered oxides by involving structural anions, which necessitates high voltages and complex charge compensation mechanisms convoluted by degradation reactions. We report a detailed structural and spectroscopic analysis of the multielectron material Li2Ru0.3Mn0.7O3, chosen due to its low Ru content. Ex situ and operando spectroscopic data over multiple cycles highlight the changing charge compensation mechanism. Notably, over half of the first-cycle capacity is attributed to O2 gas evolution and reversible O redox is minimal. Instead, reduced Ru and Mn species are detected in the bulk and on the surface, which then increasingly contribute to charge compensation as more metal reduction occurs with cycling. Permanent structural changes linked to metal migration are observed with EXAFS and Raman analysis.	Dec 2022
I07-Surface & interface diffraction	Ethylenediamine addition improves performance and suppresses phase instabilities in mixed-halide perovskites Margherita Taddei , Joel A. Smith , Benjamin M. Gallant , Suer Zhou , Robert J. E. Westbrook , Yangwei Shi , Jian Wang , James N. Drysdale , Declan P. Mccarthy , Stephen Barlow , Seth R. Marder , Henry J. Snaith , David S. Ginger Acs Energy Letters DOI: 10.1021/acsenergylett.2c01998 Diamond Proposal Number(s): [30612] Show Abstract ▼ Abstract: We show that adding ethylenediamine (EDA) to perovskite precursor solutions improves the photovoltaic device performance and material stability of high-bromide-content, methylammonium-free, formamidinium cesium lead halide perovskites FA1–xCsxPb(I1–yBry)3, which are currently of interest for perovskite-on-Si tandem solar cells. Using spectroscopy and hyperspectral microscopy, we show that the additive improves film homogeneity and suppresses the phase instability that is ubiquitous in high-Br perovskite formulations, producing films that remain stable for over 100 days in ambient conditions. With the addition of 1 mol % EDA, we demonstrate 1.69 eV-gap perovskite single-junction p-i-n devices with a VOC of 1.22 V and a champion maximum-power-point-tracked power conversion efficiency of 18.8%, comparable to the best reported methylammonium-free perovskites. Using nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction techniques, we show that EDA reacts with FA+ in solution, rapidly and quantitatively forming imidazolinium cations. It is the presence of imidazolinium during crystallization which drives the improved perovskite thin-film properties.	Nov 2022
I09-Surface and Interface Structural Analysis	Computational prediction and experimental realization of earth-abundant transparent conducting oxide Ga-doped ZnSb2O6 Adam J. Jackson , Benjamin J. Parrett , Joe Willis , Alex M. Ganose , W. W. Winnie Leung , Yuhan Liu , Benjamin A. D. Williamson , Timur K. Kim , Moritz Hoesch , Larissa S. I. Veiga , Raman Kalra , Jens Neu , Charles A. Schmuttenmaer , Tien-Lin Lee , Anna Regoutz , Tung-Chun Lee , Tim D. Veal , Robert G. Palgrave , Robin Perry , David O. Scanlon Acs Energy Letters DOI: 10.1021/acsenergylett.2c01961 Diamond Proposal Number(s): [24449] Open Access Show Abstract ▼ Abstract: Transparent conducting oxides have become ubiquitous in modern optoelectronics. However, the number of oxides that are transparent to visible light and have the metallic-like conductivity necessary for applications is limited to a handful of systems that have been known for the past 40 years. In this work, we use hybrid density functional theory and defect chemistry analysis to demonstrate that tri-rutile zinc antimonate, ZnSb2O6, is an ideal transparent conducting oxide and to identify gallium as the optimal dopant to yield high conductivity and transparency. To validate our computational predictions, we have synthesized both powder samples and single crystals of Ga-doped ZnSb2O6 which conclusively show behavior consistent with a degenerate transparent conducting oxide. This study demonstrates the possibility of a family of Sb(V)-containing oxides for transparent conducting oxide and power electronics applications.	Oct 2022
I14-Hard X-ray Nanoprobe	Multimodal microscale imaging of textured perovskite–silicon tandem solar cells Elizabeth M. Tennyson , Kyle Frohna , William K. Drake , Florent Sahli , Terry Chien-Jen Yang , Fan Fu , Jérémie Werner , Cullen Chosy , Alan R. Bowman , Tiarnan A. S. Doherty , Quentin Jeangros , Christophe Ballif , Samuel D. Stranks Acs Energy Letters DOI: 10.1021/acsenergylett.1c00568 Diamond Proposal Number(s): [20420] Open Access Show Abstract ▼ Abstract: Halide perovskite/crystalline silicon (c-Si) tandem solar cells promise power conversion efficiencies beyond the limits of single-junction cells. However, the local light-matter interactions of the perovskite material embedded in this pyramidal multijunction configuration, and the effect on device performance, are not well understood. Here, we characterize the microscale optoelectronic properties of the perovskite semiconductor deposited on different c-Si texturing schemes. We find a strong spatial and spectral dependence of the photoluminescence (PL) on the geometrical surface constructs, which dominates the underlying grain-to-grain PL variation found in halide perovskite films. The PL response is dependent upon the texturing design, with larger pyramids inducing distinct PL spectra for valleys and pyramids, an effect which is mitigated with small pyramids. Further, optimized quasi-Fermi level splittings and PL quantum efficiencies occur when the c-Si large pyramids have had a secondary smoothing etch. Our results suggest that a holistic optimization of the texturing is required to maximize light in- and out-coupling of both absorber layers and there is a fine balance between the optimal geometrical configuration and optoelectronic performance that will guide future device designs.	May 2021
	Operando measurement of layer breathing modes in lithiated graphite Hossein Yadegari , Mohamed A. Koronfel , Kang Wang , Daisy B. Thornton , Ifan E. L. Stephens , Carla Molteni , Peter D. Haynes , Mary P. Ryan Acs Energy Letters 220, 1633 - 1638 DOI: 10.1021/acsenergylett.1c00494 Show Abstract ▼ Abstract: Despite their ubiquitous usage and increasing societal dependence on Li-ion batteries, there remains a lack of detailed empirical evidence of Li intercalation/deintercalation into graphite even though this process dictates the performance, longevity, and safety of the system. Here, we report direct detection and dissociation of specific crystallographic phases in the lithiated graphite, which form through a stepwise staging process. Using operando measurements, LiC18, LiC12, and LiC6 phases are observed via distinct low-frequency Raman features, which are the result of displacement of the graphite lattice by induced local strain. Density functional theory calculations confirm the nature of the Raman-active vibrational modes, to the layer breathing modes (LBMs) of the lithiated graphite. The new findings indicate graphene-like characteristics in the lithiated graphite under the deep charged condition due to the imposed strain by the inserted Li. Moreover, our approach also provides a simple experimental tool to measure induced strain in the graphite structure under full intercalation conditions.	Apr 2021
	Rapid recombination by cadmium vacancies in CdTe Seán R. Kavanagh , Aron Walsh , David O. Scanlon Acs Energy Letters 6, 1392 - 1398 DOI: 10.1021/acsenergylett.1c00380 Open Access Show Abstract ▼ Abstract: CdTe is currently the largest thin-film photovoltaic technology. Non-radiative electron–hole recombination reduces the solar conversion efficiency from an ideal value of 32% to a current champion performance of 22%. The cadmium vacancy (VCd) is a prominent acceptor species in p-type CdTe; however, debate continues regarding its structural and electronic behavior. Using ab initio defect techniques, we calculate a negative-U double-acceptor level for VCd, while reproducing the VCd1– hole–polaron, reconciling theoretical predictions with experimental observations. We find the cadmium vacancy facilitates rapid charge-carrier recombination, reducing maximum power-conversion efficiency by over 5% for untreated CdTe—a consequence of tellurium dimerization, metastable structural arrangements, and anharmonic potential energy surfaces for carrier capture.	Mar 2021
	Operando generated ordered heterogeneous catalyst for the selective conversion of CO2 to methanol Arjun Cherevotan , Jithu Raj , Lakshay Dheer , Soumyabrata Roy , Shreya Sarkar , Risov Das , Chathakudath P. Vinod , Shaojun Xu , Peter Wells , Umesh V. Waghmare , Sebastian C. Peter Acs Energy Letters DOI: 10.1021/acsenergylett.0c02614 Show Abstract ▼ Abstract: The discovery of new materials for efficient transformation of carbon dioxide (CO2) into desired fuel can revolutionize large-scale renewable energy storage and mitigate environmental damage due to carbon emissions. In this work, we discovered an operando generated stable Ni–In kinetic phase that selectively converts CO2 to methanol (CTM) at low pressure compared to the state-of-the-art materials. The catalytic nature of a well-known methanation catalyst, nickel, has been tuned with the introduction of inactive indium, which enhances the CTM process. The remarkable change in the mechanistic pathways toward methanol production has been mapped by operando diffuse reflectance infrared Fourier transform spectroscopy analysis, corroborated by first-principles calculations. The ordered arrangement and pronounced electronegativity difference between metals are attributed to the complete shift in mechanism. The approach and findings of this work provide a unique advance toward the next-generation catalyst discovery for going beyond the state-of-the-art in CO2 reduction technologies.	Jan 2021
I11-High Resolution Powder Diffraction	In situ phase transformation on nickel-based selenides for enhanced hydrogen evolution reaction in alkaline medium Lingling Zhai , Tsz Woon Benedict Lo , Zheng-Long Xu , Jonathan Potter , Jiaying Mo , Xuyun Guo , Chiu Chung Tang , Shik Chi Edman Tsang , Shu Ping Lau Acs Energy Letters DOI: 10.1021/acsenergylett.0c01385 Diamond Proposal Number(s): [23230] Show Abstract ▼ Abstract: Identification of the active species in electrocatalysts toward hydrogen evolution reaction (HER) is of great significance for the development of the catalytic industry; however, it is still the subject of considerable controversy. Herein, we applied operando synchrotron X-ray powder diffraction (SXRD) in the NiSe2 electrocatalyst system, and an in situ phase transformation from cubic NiSe2 to hexagonal NiSe was revealed. The NiSe phase showed an enhanced catalytic activity. Operando Raman spectroscopy verified the decomposition of NiSe2 during HER. Theoretical calculations suggested that the charge transfers from the Se site to Ni site during this evolution process, leading to an increased conductivity and a shifting up of d-band center, which is attributed to the enhanced activity. The generated NiSe phase acts as the “real” active species. Our work unravels the underlying phase transition of the electrocatalyst on reductive conditions in alkaline medium and highlights the significance of identifying the intrinsic active sites under realistic reaction conditions.	Jul 2020
	Transition metal migration can facilitate ionic diffusion in defect garnet based intercalation electrodes Nicholas H Bashian , Samantha Abdel-Latif , Mateusz Zuba , Kent J. Griffith , Alex M. Ganose , Joseph W. Stiles , Shiliang Zhou , David O. Scanlon , Louis F. J. Piper , Brent Melot Acs Energy Letters DOI: 10.1021/acsenergylett.0c00376 Show Abstract ▼ Abstract: The importance of metal migration during multi-electron redox activity has been characterized, revealing a competing demand to satisfy bonding requirements and local strains in structures upon alkali intercalation. The local structural evolution required to accommodate intercalation in Y2(MoO4)3 and Al2(MoO4)3 has been contrasted by operando characterization methods, including X-ray absorption spectroscopy and diffraction, along with nuclear magnetic resonance measurements. Computational modeling further rationalized behavioral differences. The local structure of Y2(MoO4)3 was maintained upon lithiation while the structure of Al2(MoO4)3 underwent substantial local atomic rearrangements as the stronger ionic character of the bonds in Al2(MoO4)3 allowed Al to mix off its starting octahedral position to accommodate strain during cycling. However, this mixing was prevented in the more covalent Y2(MoO4)3 which accommodated strain through rotational motion of polyhedral subunits. Knowing that an increased ionic character can facilitate the diffusion of redox-inactive metals when cycling multi-electron electrodes offers a powerful design principle when identifying next-generation intercalation hosts.	Apr 2020
I09-Surface and Interface Structural Analysis	Quantifying the capacity contributions during activation of Li2MnO3 Jatinkumar Rana , Joseph K. Papp , Zachary Lebens-Higgins , Mateusz Zuba , Lori A. Kaufman , Anshika Goel , Richard Schmuch , Martin Winter , M. Stanley Whittingham , Wanli Yang , Bryan D. Mccloskey , Louis F. J. Piper Acs Energy Letters DOI: 10.1021/acsenergylett.9b02799 Diamond Proposal Number(s): [22250] Show Abstract ▼ Abstract: Though Li2MnO3 was originally considered to be electrochemically inert, its observed activation has spawned a new class of Li-rich layered compounds that deliver capacities beyond the traditional transition-metal redox limit. Despite progress in our understanding of oxygen redox in Li-rich compounds, the underlying origin of the initial charge capacity of Li2MnO3 remains hotly contested. To resolve this issue, we review all possible charge compensation mechanisms including bulk oxygen redox, oxidation of Mn4+, and surface degradation for Li2MnO3 cathodes displaying capacities exceeding 350 mAh g–1. Using elemental and orbital selective X-ray spectroscopy techniques, we rule out oxidation of Mn4+ and bulk oxygen redox during activation of Li2MnO3. Quantitative gas-evolution and titration studies reveal that O2 and CO2 release accounted for a large fraction of the observed capacity during activation with minor contributions from reduced Mn species on the surface. These studies reveal that, although Li2MnO3 is considered critical for promoting bulk anionic redox in Li-rich layered oxides, Li2MnO3 by itself does not exhibit bulk oxygen redox or manganese oxidation beyond its initial Mn4+ valence.	Jan 2020

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