|
|
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
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
|
Diamond Proposal Number(s):
[23230]
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
|
|
|
|
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
|
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
Diamond Proposal Number(s):
[22250]
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
|
|
I13-2-Diamond Manchester Imaging
|
Fu
Sun
,
Dong
Zhou
,
Xin
He
,
Markus
Osenberg
,
Kang
Dong
,
Libao
Chen
,
Shilin
Mei
,
Andre
Hilger
,
Henning
Markötter
,
Yan
Lu
,
Shanmu
Dong
,
Shashidhara
Marathe
,
Christoph
Rau
,
Xu
Hou
,
Jie
Li
,
Marian Cristian
Stan
,
Martin
Winter
,
Robert
Dominko
,
Ingo
Manke
Diamond Proposal Number(s):
[18936]
Abstract: Although a great variety of strategies to suppress Li dendrite have been proposed for lithium metal batteries (LMBs), a deeper understanding of the factors playing a crucial role during extended electrochemical cycling is often lacking. Herein, the morphological reversibility of the Li-based anode for next-generation batteries under three prevalent strategies, i.e., the use of Li–Al alloys, polymer coating, and anodic aluminum oxide (AAO) membrane attachment, has been sophisticatedly investigated by nondestructive visualization. The characterizations clearly capture the unprecedented morphological evolution of the Li-based anode during the electrochemical cycling. Furthermore, the results unambiguously indicate the formation of the “dead” electrochemically generated porous structures regardless of >99% cycling efficiency shown in Li symmetric cells in all three cell configurations. The results presented here shed light on further understanding of the morphological evolution of the Li anode under different scenarios, and it also enlightens us on new research activities that may assist in propelling the commercialization of LMBs.
|
Dec 2019
|
|
I07-Surface & interface diffraction
|
Baocai
Du
,
Renyong
Geng
,
Wei
Li
,
Donghui
Li
,
Yuchao
Mao
,
Mengxue
Chen
,
Xue
Zhang
,
Joel A.
Smith
,
Rachel C.
Kilbride
,
Mary E.
O'kane
,
Dan
Liu
,
David G.
Lidzey
,
Weihua
Tang
,
Tao
Wang
Diamond Proposal Number(s):
[22651]
Abstract: The insufficient phase separation between polymer donors and non-fullerene acceptors (NFAs) featuring with low-structural orders disrupts efficient charge transport and increases charge recombination, consequently limits the maximum achievable power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, an NFA IT-M has been added as the third component into the PBDB-T:m-INPOIC OSCs, and is shown to effectively tune the phase separation between donor and acceptor molecules, although all components in the ternary system exhibit low degrees of structural orders. The incorporation of 10 wt% IT-M into a PBDB-T:m-INPOIC binary host blend appreciably increases the length scale of phase separation, creating continuous pathways which increase and balance charge transport. This leads to an enhanced photovoltaic performance from 12.8% in the binary cell to 13.9% for the ternary cell with simultaneously improved open-circuit voltage, short-circuit current and fill factor. This work highlights the beneficial role of ternary components in controlling the morphology of the active layer for high performance OSCs.
|
Sep 2019
|
|
B18-Core EXAFS
|
Chunzhen
Yang
,
Maria
Batuk
,
Quentin
Jacquet
,
Gwenaëlle
Rousse
,
Wei
Yin
,
Leiting
Zhang
,
Joke
Hadermann
,
Artem
Abakumov
,
Giannantonio
Cibin
,
Alan
Chadwick
,
Jean-marie
Tarascon
,
Alexis
Grimaud
Diamond Proposal Number(s):
[12559]
Abstract: Multiple electrochemical processes are involved at the catalyst/electrolyte interface during the oxygen evolution reaction (OER). With the purpose of elucidating the complexity of surface dynamics upon OER, we systematically studied two Ni-based crystalline oxides (LaNiO3-δ and La2Li0.5Ni0.5O4) and compared them with the state-of-the-art Ni-Fe (oxy)hydroxide amorphous catalyst. Electrochemical measurements such as rotating ring disk electrode (RRDE) and electrochemical quartz microbalance microscopy (EQCM), coupled with a series of physical characterizations including transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) are conducted to unravel the exact pH effect on both the OER activity and the catalyst stability. We demonstrate that for Ni-based crystalline catalysts the rate for surface degradation depends on the pH and is greater than the rate for surface reconstruction. This behavior is unlike for amorphous Ni oxyhydroxide catalyst which is found more stable and pH independent.
|
Nov 2018
|
|
|
|
Nicholas H.
Bashian
,
Shiliang
Zhou
,
Mateusz
Zuba
,
Alex M.
Ganose
,
Joseph W.
Stiles
,
Allyson
Ee
,
David S.
Ashby
,
David O.
Scanlon
,
Louis F. J.
Piper
,
Bruce S.
Dunn
,
Brent C.
Melot
Abstract: Understanding the structural transformations that materials undergo during the insertion and deinsertion of Li-ions is crucial for designing high performance intercalation hosts as these deformations can lead to significant capacity fade over time. Here we present a study of the metallic defect perovskite ReO3, with the goal of determining whether these distortions are driven by polaronic charge transport (i.e. the electrons and ions moving through the lattice in a coupled way) due to the semiconducting nature of most oxide hosts. Employing a range of techniques including galvanostatic/potentiometric electrochemical probes, operando X-ray diffraction, X-ray photoelectron spectroscopy, and density functional theory calculations we nd that the cubic structure of ReO3 experiences multiple phase changes involving the correlated twisting of rigid octahedral subunits during the insertion of two equivalents of Li-ions. This extensive rearrangement of the structure results in exceptionally poor long-term cyclability due to large strains that result within the structure, all in spite of the fact that the phase retains its metallic character for all values of Li content from ReO3 to Li2ReO3. These results suggest that phase transformations during alkali ion intercalation are the result of local strains in the lattice and not exclusively due to polaron migration.
|
Sep 2018
|
|
I07-Surface & interface diffraction
|
Diamond Proposal Number(s):
[17223]
Abstract: Tin-lead mixed metal hybrid perovskites with tunable band gaps are attractive candidates to be used as the low-band gap cell in high efficiency tandem solar cells. Nevertheless, perovskites containing tin have a greater propensity to degrade due to the fast oxidation of Sn2+ to Sn4+, which is a restrictive factor in the development of these materials. Although significant improvements are achieved with Pb:Sn mixed-metal perovskites, in comparison to neat Sn perovskites, the intrinsic instability may still pose a threat to long-term operation. For neat Pb perovskites, two dimensional (2D) hybrid perovskites, where n layers of inorganic material are separated by a long chain organic cation, generally exhibit greater stability but have lower photovoltaic performance characteristics, motivating the study of 2D/3D mixed dimension systems to realize both high efficiency and stability. In this report we demonstrate such optimal compromise between performance and stability using formamidinium, cesium and t-butylammonium as A-site cations with Pb:Sn mixed metal low band gap perovskites. As determined by film structure measurements, the optimised 2D perovskite phases facilitate improved luminescence efficiency, which we infer to be via surface defect site passivation. Perovskite solar cells based on n = 4 and n = 5 lead-tin perovskites achieved power conversion efficiencies of up to 9.3% and 10.6%, respectively and correspondingly retained 47% and 29% of their initial efficiency during storage in nitrogen for 2000 hours. A similar stability trend for n = 4 over n = 5 was also observed for unencapsulated devices during continuous operation under combined air atmosphere and temperature for 10 hours, resulting in improved stability over the 3D lead-tin counterpart.
|
Aug 2018
|
|
I07-Surface & interface diffraction
I12-JEEP: Joint Engineering, Environmental and Processing
|
Alex J.
Barker
,
Aditya
Sadhanala
,
Felix
Deschler
,
Marina
Gandini
,
Satyaprasad P.
Senanayak
,
Phoebe M.
Pearce
,
Edoardo
Mosconi
,
Andrew
Pearson
,
Yue
Wu
,
Ajay Ram
Srimath Kandada
,
Tomas
Leitjens
,
Filippo
De Angelis
,
Sian E.
Dutton
,
Annamaria
Petrozza
,
Richard H.
Friend
Diamond Proposal Number(s):
[11454, 12436]
Abstract: Solution processable lead halide perovskites show immense promise for use in photovoltaics and other optoelectronic applications. The ability to tune their bandgap by alloying various halide anions (for example in CH3NH3Pb(I1-xBrx)3, 0
|
May 2017
|
|
