B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
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Zhangxiang
Hao
,
Junrun
Feng
,
Yiyun
Liu
,
Liqun
Kang
,
Bolun
Wang
,
Junwen
Gu
,
Lin
Sheng
,
Ruoyu
Xu
,
Sushila
Marlow
,
Dan J.l.
Brett
,
Yunhui
Huang
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[22572, 21641, 22604, 26717, 29407]
Abstract: Polymer materials offer controllable structure-dependent performances in separation, catalysis and drug release. Their molecular structures can be precisely tailored to accept Li+ for energy storage applications. Here the design of sp2 carbon-based polyphenylene (PPH) with high lithium-ion uptakes and long-term stability is reported. Linear-PPH (L-PPH) exceeds the performance of crosslink-PPH (C-PPH), due to the fact that it has an ordered lamellar structure, promoting the Li+ intercalation/deintercalation channel. The L-PPH cell shows a clear charge and discharge plateau at 0.35 and 0.15 V vs. Li+/Li, respectively, which is absent in the C-PPH cell. The Li+ storage capacity of L-PPH is five times that of the C-PPH. The reversible storage capacity is further improved to 261 mAh g−1 by functionalizing the L-PPH with the –SO3H groups. In addition, the Li-intercalated structures of C-PPH and L-PPH are investigated via near-edge X-ray absorption fine structure (NEXAFS), suggesting the high reversible Li+ - C=C bond interaction at L-PPH. This strategy, based on new insight into sp2 functional groups, is the first step toward a molecular understanding of the structure storage-capacity relationship in sp2 carbon-based polymer.
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Jul 2021
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B18-Core EXAFS
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Siyu
Zhao
,
Ruikuan
Xie
,
Liqun
Kang
,
Manni
Yang
,
Xingyu
He
,
Wenyao
Li
,
Ryan
Wang
,
Dan J. L.
Brett
,
Guanjie
He
,
Guoliang
Chai
,
Ivan P.
Parkin
Diamond Proposal Number(s):
[19850]
Open Access
Abstract: It remains a challenge to develop efficient electrocatalysts in neutral media for hydrogen evolution reaction (HER) due to the sluggish kinetics and switch of the rate determining step. Although metal phosphides are widely used HER catalysts, their structural stability is an issue due to oxidization, and the HER performance in neutral media requires improvement. Herein, a new material, i.e., grapevine‐shaped N‐doped iron phosphide on carbon nanotubes, as an efficient HER catalyst in neutral media is developed. The optimized catalyst shows an overpotential of 256 mV at a large current density of 65 mA cm−2, which is even 10 mV lower than that of the commercial 20% Pt/C catalyst. The excellent performance of the catalyst is further studied by combined computational and experimental techniques, which proves that the interaction between nitrogen and iron phosphides can provide more efficient active structures and stabilize the metal phosphide electrocatalysts for HER.
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May 2021
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Liqun
Kang
,
Bolun
Wang
,
Andreas T.
Güntner
,
Siyuan
Xu
,
Xuhao
Wan
,
Yiyun
Liu
,
Sushila
Marlow
,
Yifei
Ren
,
Diego
Gianolio
,
Chiu C.
Tang
,
Vadim
Murzin
,
Hiroyuki
Asakura
,
Qian
He
,
Shaoliang
Guan
,
Juan J.
Velasco-Vélez
,
Sotiris E.
Pratsinis
,
Yuzheng
Guo
,
Feng Ryan
Wang
Open Access
Abstract: Electronic metal‐support interaction (EMSI) describes the electron flow between metal sites and a metal oxide support. It is generally used to follow the mechanism of redox reactions. In the study of CuO‐CeO2 redox, an additional flow of electron from metallic Cu to surface carbon species is observed via a combination of operando X‐ray absorption spectroscopy, synchrotron X‐ray powder diffraction, near ambient pressure‐near edge X‐ray absorption fine structure, and diffuse reflectance infrared Fourier transform spectroscopy. An electronic metal‐support‐carbon interaction (EMSCI) is proposed to explain the reaction pathway of CO oxidation. The EMSCI provides a complete picture of the mass and electron flow, which will help predict and improve the catalytic performance in the selective activation of CO2 , carbonate or carbonyl species in C1 chemistry.
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Mar 2021
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E01-JEM ARM 200CF
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Diamond Proposal Number(s):
[20643]
Abstract: The magnesium–sulfur (Mg-S) battery may be a safer alternative for the lithium-sulfur battery because Mg plating usually proceeds without dendrite formation. Here, we correlate the thermal runaway of Mg-S battery with the associated change of electrolyte vapour pressure via battery testing calorimetery. Over-pressure builds up along with the programmed heating of the cell, and as a result, the thermal runaway is triggered at 20 to 45 K over the electrolyte boiling point, corresponding to 70 to 150 kPa pressure difference between the cell and the environment. The distinct performance-safety-cost behaviours of three ether type of electrolytes stems from the different CH2CH2O chain lengths. Such molecular insight will serve as a fundamental guideline in choosing and designing the desired electrolyte that simultaneously achieves a high explosion limit and good electrochemical performance.
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Jan 2021
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
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Jian
Guo
,
Liqun
Kang
,
Xuekun
Lu
,
Siyu
Zhao
,
Jianwei
Li
,
Paul R.
Shearing
,
Ryan
Wang
,
Dan J. L.
Brett
,
Guanjie
He
,
Guoliang
Chai
,
Ivan P.
Parkin
Diamond Proposal Number(s):
[22572, 20847]
Abstract: Developing cost-effective and durable air-cathodes is crucial for improving metal-air batteries. Most reports of cathode formulation involve preparing bi-functional electrocatalysts from wet chemistry or solid-state synthesis, followed by pasting onto a substrate. In this work, the cathodes generated from electrochemical activation of normal carbon paper substrates were directly used in Zn-air batteries. The self-activated carbon paper substrate without any additional electrocatalysts exhibits an impressive cycling stability (more than 165 hours for 1,000 cycles) and a small discharge-charge voltage gap. After the activation, the maximum power density and electrochemical surface area were increased by over 40 and 1,920 times respectively. It is discovered that substrates after activation can be directly used as a cathode. The new method is scalable, inexpensive and produces near best in class performance. The mechanism behind this enhancement is due to the creation of oxygen functional groups within the cathode, which overcame slow kinetics, enhanced wettability and enabled optimum three-phase boundaries.
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Dec 2020
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B18-Core EXAFS
E01-JEM ARM 200CF
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Diamond Proposal Number(s):
[15151, 21370, 19246, 22572]
Abstract: Selective transformation of biomass feedstocks to platform molecules is a key pursuit for sustainable chemical production. Compared to petrochemical processes, biomass transformation requires the defunctionalization of highly polar molecules at relatively low temperatures. As a result, catalysts based on functional organic polymers may play a prominent role. Targeting the hydrogenolysis of the platform chemical 5-hydroxymethylfurfural (5-HMF), here, we design a polyphenylene (PPhen) framework with purely sp2-hybridized carbons that can isolate 5-HMF via π–π stacking, preventing hemiacetal and humin formation. With good swellability, the PPhen framework here has successfully supported and dispersed seven types of metal particles via a newly developed swelling-impregnation method, including Ru, Pt, Au, Fe, Co, Ni, and Cu. Ru/PPhen is studied for 5-HMF hydrogenolysis, achieving a 92% yield of 2,5-dimethylfuran (DMF) under mild conditions, outperforming the state-of-the-art catalysts reported in the literature. In addition, PPhen helps perform a solventless reaction, achieving direct 5-HMF to DMF conversion in the absence of any liquid solvent or reagent. This approach in designing support–reactant/solvent/metal interactions will play an important role in surface catalysis.
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Nov 2020
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E01-JEM ARM 200CF
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Yiding
Jiao
,
Liqun
Kang
,
Jasper
Berry-Gair
,
Kit
Mccoll
,
Jianwei
Li
,
Haobo
Dong
,
Hao
Jiang
,
Ryan
Wang
,
Furio
Corà
,
Dan J. L.
Brett
,
Guanjie
He
,
Ivan
Parkin
Diamond Proposal Number(s):
[24450]
Open Access
Abstract: The primary issue faced by MnO2 cathode materials for aqueous Zn-ion batteries (AZIBs) is the occurrence of structural transformations during cycling, resulting in unstable capacity output. Pre-intercalating closely bonded ions into the MnO2 structures has been demonstrated as an effective approach to combat this. However, mechanisms of the pre-intercalation remain unclear. Herein, two distinct δ-MnO2 (K0.28MnO2·0.1H2O and K0.21MnO2·0.1H2O) are prepared with varying amounts of pre-intercalated K+ and applied as cathodes for AZIBs. The as-prepared K0.28MnO2·0.1H2O cathodes exhibit relatively high specific capacity (300 mA h g−1 at 100 mA g−1), satisfactory rate performance (35% capacity recovery at 5 A g−1) and competent cyclability (ca. 95% capacity retention after 1000 cycles at 2 A g−1), while inferior cyclability and rate performance are observed in K0.21MnO2·0.1H2O. A stable δ-MnO2 phase is observed upon cycling, with the reversible deposition of Zn4SO4(OH)6·5H2O (ZSH), ion migration between electrodes and synchronous transition of Mn valence states. This work firstly and systematically reveals the role of the pre-intercalated ions via density functional theory simulations and show that above a threshold K/Mn ratio of ca. 0.26, the K ions suppress structural transformations by stabilizing the δ phase. To demonstrate its commercial potential, AZIBs with high-loading active materials are fabricated, which deliver adequate energy and power densities compared with most commercial devices.
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Nov 2020
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E01-JEM ARM 200CF
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Ruoyu
Xu
,
Jingwei
Xiang
,
Junrun
Feng
,
Xuekun
Lu
,
Zhangxiang
Hao
,
Liqun
Kang
,
Ming
Li
,
Yunsong
Wu
,
Chun
Tan
,
Yiyun
Liu
,
Guanjie
He
,
Dan J. L.
Brett
,
Paul R.
Shearing
,
Lixia
Yuan
,
Yunhui
Huang
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[17559, 19318, 19246, 20643]
Abstract: The lithium-sulfur (Li-S) batteries have high theoretical energy density, exceeding that of the lithium-ion batteries. However, their practical applications are hindered by the capacity decay due to lithium polysulfide shuttle effect and sulfur volume expansion. Here, we design a S@hollow carbon with porous shell/MnOx (S@HCS/MnOx) cathode to accommodate and immobilize sulfur and polysulfides, and develop a non-destructive technique X-ray computed tomography (X-ray CT) to in situ visualize the volume expansion of Li-S cathode. The designed cathode achieves a specific capacity of ~1100 mAh g-1 at 0.2 C with a fade rate of 0.18% per cycle over 300 cycles. The X-ray CT shows that only 16% volume expansion and 70% volume fraction of solid sulfur remaining in the S@HCS/MnOx cathode, superior to the commercial cathode with 40% volume expansion and 5% volume remaining of solid sulfur particles. This is the first reported visualization evidence for the effectiveness of hollow carbon structure in accommodating cathode volume expansion and immobilizing sulfur shuttling. X-ray CT can serve as a powerful in situ tool to trace the active materials and then feedback to the structure design, which helps develop efficient and reliable energy storage systems.
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Oct 2020
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B18-Core EXAFS
E01-JEM ARM 200CF
E02-JEM ARM 300CF
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Liqun
Kang
,
Bolun
Wang
,
Adam
Thetford
,
Ke
Wu
,
Mohsen
Danaie
,
Qian
He
,
Emma
Gibson
,
Ling-Dong
Sun
,
Hiroyuki
Asakura
,
Richard
Catlow
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[16966, 17559, 18909, 19246, 19318, 20643, 20847, 17377, 15151, 14239]
Open Access
Abstract: Ru(II) compounds are widely used in catalysis, photocatalysis and medical applications. They are usually obtained in reductive environment as molecular O 2 can oxidize Ru(II) to Ru(III) and Ru(IV). Here we report the design, identification and evolution of an air‐stable surface ‐[bipy‐Ru(II)(CO) 2 Cl 2 ] site that is covalently mounted onto a polyphenylene framework. Such Ru(II) site was obtained by reduction of ‐[bipy‐Ru(III)Cl 4 ] ‐ with simultaneous ligand exchange from Cl ‐ to CO. This structural evolution was witnessed by a combination of in situ X‐ray and infrared spectroscopy studies. The ‐[bipy‐Ru(II)(CO) 2 Cl 2 ] site enables oxidation of CO with a turnover frequency of 0.73 × 10 ‐2 s ‐1 at 462 K, while the Ru(III) site is completely inert. This work contributes to the studies of structure‐activity relationship by demonstrating a practical control over both geometric and electronic structures of single‐site catalysts at molecular level, which can be further applied in other single site catalyst researches.
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Sep 2020
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B18-Core EXAFS
E01-JEM ARM 200CF
E02-JEM ARM 300CF
I11-High Resolution Powder Diffraction
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Liqun
Kang
,
Bolun
Wang
,
Qiming
Bing
,
Michal
Zalibera
,
Robert
Büchel
,
Ruoyu
Xu
,
Qiming
Wang
,
Yiyun
Liu
,
Diego
Gianolio
,
Chiu C.
Tang
,
Emma K.
Gibson
,
Mohsen
Danaie
,
Christopher
Allen
,
Ke
Wu
,
Sushila
Marlow
,
Ling-Dong
Sun
,
Qian
He
,
Shaoliang
Guan
,
Anton
Savitsky
,
Juan J.
Velasco-Vélez
,
June
Callison
,
Christopher W. M.
Kay
,
Sotiris E.
Pratsinis
,
Wolfgang
Lubitz
,
Jing-Yao
Liu
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[15151, 15763, 16966, 17377, 19072, 19246, 20939, 17559, 24285, 19318, 19850]
Open Access
Abstract: Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, we achieve selective oxygen (O2) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3d orbitals of isolated copper (Cu) sites. Operando X-ray absorption spectroscopy, electron paramagnetic resonance and density-functional theory simulations are used to demonstrate that a [Cu(I)O2]3− site selectively adsorbs molecular O2, forming a rarely reported electrophilic η2-O2 species at 298 K. Assisted by neighbouring Ce(III) cations, η2-O2 is finally reduced to two O2−, that create two Cu–O–Ce oxo-bridges at 453 K. The isolated Cu(I)/(II) sites are ten times more active in CO oxidation than CuO clusters, showing a turnover frequency of 0.028 ± 0.003 s−1 at 373 K and 0.01 bar PCO. The unique electronic structure of [Cu(I)O2]3− site suggests its potential in selective oxidation.
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Aug 2020
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