Co-reporter:Wei Xiong, Zheng Guo, Hao Li, Ran Zhao, and Xinwei Wang
ACS Energy Letters - New in 2016 December 8, 2017 Volume 2(Issue 12) pp:2778-2778
Publication Date(Web):November 7, 2017
DOI:10.1021/acsenergylett.7b01056
A rational bottom-up engineering strategy for efficient electrocatalysts based on atomic layer deposition (ALD) is reported. The strategy involves compositional optimization of surface catalyst material by ALD for high specific activity and geometric optimization of electrode structure for high surface area. The two optimizations are decoupled herein, because the conformal ALD ensures that the coating of the catalyst does not depend on the substrate geometry. To demonstrate this strategy, we choose ternary FexCo1–xSy compound as the catalyst for electrochemical hydrogen evolution reaction (HER). Compositional optimization shows that Fe0.54Co0.46S0.92 is the best composition for high specific HER activity, and it is therefore chosen to be conformally coated by ALD on a high-surface-area CNTs/CC (carbon nanotubes on carbon cloth) electrode. The synthesized Fe0.54Co0.46S0.92/CNTs/CC electrode exhibits a fairly low HER overpotential of −70 mV for achieving −10 mA/cm2 in current density in alkaline solution, which demonstrates the effectiveness of this ALD-based engineering strategy.
Co-reporter:Qian Sheng;Yanbo Xie;Jun Li;Jianming Xue
Chemical Communications 2017 vol. 53(Issue 45) pp:6125-6127
Publication Date(Web):2017/06/01
DOI:10.1039/C7CC01047H
Synthetic conical nanochannels have gained attention for their ion rectification behavior, which can be used to mimic the functionalities of biological ion channels. Employing these nanochannels and inspired by biological synaptic dynamics, we herein demonstrate a new nanofluidic device as a memristor, the ion transport conductance of which depends on the history of its ion flow. The nanofluidic memristors show excellent repeatability, high ON/OFF ratios, and sufficiently long retention times, which are highly desirable for logic control and neuromorphic engineering applications in nanofluidic systems as well as for fundamental transport studies of ionic liquids on a nanoscale.
Co-reporter:Ran ZhaoYuanhong Gao, Zheng Guo, Yantao Su, Xinwei Wang
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 2) pp:
Publication Date(Web):December 26, 2016
DOI:10.1021/acsami.6b12832
Ultrathin atomic-layer-deposited (ALD) vanadium oxide (VOx) interlayer has recently been demonstrated for remarkably reducing the contact resistance in organic electronic devices (Adv. Funct. Mater. 2016, 26, 4456). Herein, we present an in situ photoelectron spectroscopy investigation (including X-ray and ultraviolet photoelectron spectroscopies) of ALD VOx grown on pentacene to understand the role of the ALD VOx interlayer for the improved contact resistance. The in situ photoelectron spectroscopy characterizations allow us to monitor the ALD growth process of VOx and trace the evolutions of the work function, pentacene HOMO level, and VOx defect states during the growth. The initial VOx growth is found to be partially delayed on pentacene in the first ∼20 ALD cycles. The underneath pentacene layer is largely intact after ALD. The ALD VOx is found to contain a high density of defect states starting from 0.67 eV below the Fermi level, and the energy level of these defect states is in excellent alignment with the HOMO level of pentacene, which therefore allows these VOx defect states to provide an efficient hole-injection pathway at the contact interface.Keywords: atomic layer deposition; defect states; interface energy alignment; photoelectron spectroscopy; vanadium oxide;
Co-reporter:Hao Li;Zheng Guo
Journal of Materials Chemistry A 2017 vol. 5(Issue 40) pp:21353-21361
Publication Date(Web):2017/10/17
DOI:10.1039/C7TA06243E
The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are the key processes in many renewable energy conversion systems, and the development of high-performance non-precious bifunctional OER/ORR electrocatalysts is of crucial importance for various energy conversion devices, such as rechargeable metal–air batteries and regenerative fuel cells. Herein, we report a novel efficient bifunctional OER/ORR catalyst of Co9S8/CNT, which is synthesized using an advanced technique of atomic layer deposition (ALD) for conformally coating a uniform thin layer of Co9S8 on a high-surface-area carbon-nanotube (CNT) network scaffold. The ALD-synthesized Co9S8/CNT catalyst displays remarkable electrocatalytic performance with excellent catalytic activity and stability toward both the OER and ORR, and is further demonstrated to be a superior bifunctional oxygen catalyst for high-performance rechargeable Zn–air batteries. The fabricated aqueous rechargeable Zn–air batteries are able to deliver a remarkably high power density with superior long-term cycling stability, and the fabricated solid-state rechargeable Zn–air batteries are able to display very good flexibility and stability upon bending. Therefore, we believe that the ALD-synthesized bifunctional Co9S8/CNT electrocatalyst will have broad and promising applications for renewable energy conversion devices.
Co-reporter:Suihan Cui;Yi Wei;Tongchao Liu;Wenjun Deng;Zongxiang Hu;Yantao Su;Hao Li;Maofan Li;Hua Guo;Yong Duan;Weidong Wang;Mumin Rao;Jiaxin Zheng;Feng Pan
Advanced Energy Materials 2016 Volume 6( Issue 4) pp:
Publication Date(Web):
DOI:10.1002/aenm.201501309
Understanding and optimizing the temperature effects of Li-ion diffusion by analyzing crystal structures of layered Li(NixMnyCoz)O2 (NMC) (x + y + z = 1) materials is important to develop advanced rechargeable Li-ion batteries (LIBs) for multi-temperature applications with high power density. Combined with experiments and ab initio calculations, the layer distances and kinetics of Li-ion diffusion of LiNixMnyCozO2 (NMC) materials in different states of Li-ion de-intercalation and temperatures are investigated systematically. An improved model is also developed to reduce the system error of the “Galvanostatic Intermittent Titration Technique” with a correction of NMC particle size distribution. The Li-ion diffusion coefficients of all the NMC materials are measured from −25 to 50 °C. It is found that the Li-ion diffusion coefficient of LiNi0.6Mn0.2Co0.2O2 is the largest with the minimum temperature effect. Ab initio calculations and XRD measurements indicate that the larger Li slab space benefits to Li-ion diffusion with minimum temperature effect in layered NMC materials.
Co-reporter:Yuanhong Gao;Youdong Shao;Lijia Yan;Hao Li;Yantao Su;Hong Meng
Advanced Functional Materials 2016 Volume 26( Issue 25) pp:4456-4463
Publication Date(Web):
DOI:10.1002/adfm.201600482
Charge injection at metal/organic interface is a critical issue for organic electronic devices in general as poor charge injection would cause high contact resistance and severely limit the performance of organic devices. In this work, a new approach is presented to enhance the charge injection by using atomic layer deposition (ALD) to prepare an ultrathin vanadium oxide (VOx) layer as an efficient hole injection interlayer for organic field-effect transistors (OFETs). Since organic materials are generally delicate, a gentle low-temperature ALD process is necessary for compatibility. Therefore, a new low-temperature ALD process is developed for VOx at 50 °C using a highly volatile vanadium precursor of tetrakis(dimethylamino)vanadium and non-oxidizing water as the oxygen source. The process is able to prepare highly smooth, uniform, and conformal VOx thin films with precise control of film thickness. With this ALD process, it is further demonstrated that the ALD VOx interlayer is able to remarkably reduce the interface contact resistance, and, therefore, significantly enhance the device performance of OFETs. Multiple combinations of the metal/VOx/organic interface (i.e., Cu/VOx/pentacene, Au/VOx/pentacene, and Au/VOx/BOPAnt) are examined, and the results uniformly show the effectiveness of reducing the contact resistance in all cases, which, therefore, highlights the broad promise of this ALD approach for organic devices applications in general.
Co-reporter:Hao Li, Youdong Shao, Yantao Su, Yuanhong Gao, and Xinwei Wang
Chemistry of Materials 2016 Volume 28(Issue 4) pp:1155
Publication Date(Web):January 27, 2016
DOI:10.1021/acs.chemmater.5b04645
Vapor-phase atomic layer deposition (ALD) of nickel sulfide (NiSx) is comprehensively reported for the first time. The deposition process employs bis(N,N′-di-tert-butylacetamidinato)nickel(II) and H2S as the reactants and is able to produce fairly smooth, pure, godlevskite-structured NiSx thin films following an ideal layer-by-layer ALD growth fashion for a relatively wide process temperature range from 90–200 °C. Excellent conformal coating is demonstrated for this ALD process, as the deposited NiSx films are able to uniformly and conformally cover deep narrow trenches with aspect ratio as high as 10:1, which highlights the general and broad applicability of this ALD process for fabricating complex 3D-structured nanodevices. Further, we demonstrate the applications of this ALD NiSx for oxygen-evolution reaction (OER) electrocatalysis. The ALD NiSx is found to convert to nickel (oxy)hydrate after electrochemical aging, and the aged product shows a remarkable electrocatalytic activity and long-term stability, which is among the best electrocatalytic performance reported for nonprecious OER catalysts. Considering that ALD can be easily scaled up and integrated with 3D nanostructures, we believe that this ALD NiSx process will be highly promising for a variety of applications in future energy devices.
Co-reporter:Hao Li, Yuanhong Gao, Youdong Shao, Yantao Su, and Xinwei Wang
Nano Letters 2015 Volume 15(Issue 10) pp:6689-6695
Publication Date(Web):August 27, 2015
DOI:10.1021/acs.nanolett.5b02508
Atomic layer deposition (ALD) of cobalt sulfide (Co9S8) is reported. The deposition process uses bis(N,N′-diisopropylacetamidinato)cobalt(II) and H2S as the reactants and is able to produce high-quality Co9S8 films with an ideal layer-by-layer ALD growth behavior. The Co9S8 films can also be conformally deposited into deep narrow trenches with aspect ratio of 10:1, which demonstrates the high promise of this ALD process for conformally coating Co9S8 on high-aspect-ratio 3D nanostructures. As Co9S8 is a highly promising electrochemical active material for energy devices, we further explore its electrochemical performance by depositing Co9S8 on porous nickel foams for supercapacitor electrodes. Benefited from the merits of ALD for making high-quality uniform thin films, the ALD-prepared electrodes exhibit remarkable electrochemical performance, with high specific capacitance, great rate performance, and long-term cyclibility, which highlights the broad and promising applications of this ALD process for energy-related electrochemical devices, as well as for fabricating complex 3D nanodevices in general.
Co-reporter:Zheng Guo, Hao Li, Qiang Chen, Lijun Sang, Lizhen Yang, Zhongwei Liu, and Xinwei Wang
Chemistry of Materials 2015 Volume 27(Issue 17) pp:5988
Publication Date(Web):August 14, 2015
DOI:10.1021/acs.chemmater.5b02137
Agglomeration is a critical issue for depositing copper (Cu) thin films, and therefore, the deposition should be preferably performed below 100 °C. This work explores an atomic layer deposition (ALD) process for copper thin films deposited at temperature as low as 50 °C. The process employs copper(I)-N,N′-diisopropylacetamidinate precursor and H2 plasma, which are both highly reactive at low temperature. The deposition process below 100 °C follows an ideal self-limiting ALD fashion with a saturated growth rate of 0.071 nm/cycle. Benefitting from the low process temperature, the agglomeration of Cu thin films is largely suppressed, and the Cu films deposited at 50 °C are pure, continuous, smooth, and highly conformal, with the resistivity comparable to PVD Cu films. In-situ reaction mechanism studies by using quartz crystal microbalance and optical emission spectroscopy are followed, and the results confirm the high reactivity of the Cu amidinate precursor at low temperature. To the best of our knowledge, this is the first successful implementation of metal amidinate precursors for low-temperature (∼50 °C) ALD process. The strategy of using metal amidinate precursors in combination with highly reactive H2 plasma is believed to be extendable for the depositions of other pure metals at low temperature.
Co-reporter:Yantao Su, Suihan Cui, Zengqing Zhuo, Wanli Yang, Xinwei Wang, and Feng Pan
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 45) pp:25105
Publication Date(Web):October 26, 2015
DOI:10.1021/acsami.5b05500
High-voltage (>4.3 V) operation of LiNixMnyCozO2 (NMC; 0 ≤ x, y, z < 1) for high capacity has become a new challenge for next-generation lithium-ion batteries because of the rapid capacity degradation over cycling. In this work, we investigate the performance of LiNi0.5Mn0.3Co0.2O2 (NMC532) electrodes with and without an atomic-layer-deposited (ALD) Al2O3 layer for charging/discharging in the range from 3.0 to 4.5 V (high voltage). The results of the electrochemical measurements show that the cells with ALD Al2O3-coated NMC532 electrodes have much enhanced cycling stability. The mechanism was investigated by using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electrochemical methods. We find that the ultrathin ALD Al2O3 film can reduce the interface resistance of lithium-ion diffusion and enhance the surface stability of NMC532 by retarding the reactions at NMC532/electrolyte interfaces for preventing the formation of a new microstructure rock-salt phase NiO around the NMC532 surfaces.Keywords: atomic layer deposition; cathode materials; cycling performance; interfacial reaction; lithium-ion battery
Co-reporter:Ceming Wang, Qibin Fu, Xinwei Wang, Delin Kong, Qian Sheng, Yugang Wang, Qiang Chen, and Jianming Xue
Analytical Chemistry 2015 Volume 87(Issue 16) pp:8227
Publication Date(Web):July 23, 2015
DOI:10.1021/acs.analchem.5b01501
Nanopore-based devices have recently become popular tools to detect biomolecules at the single-molecule level. Unlike the long-chain nucleic acids, protein molecules are still quite challenging to detect, since the protein molecules are much smaller in size and usually travel too fast through the nanopore with poor signal-to-noise ratio of the induced transport signals. In this work, we demonstrate a new type of nanopore device based on atomic layer deposition (ALD) Al2O3 modified track-etched conical nanochannels for protein sensing. These devices show very promising properties of high protein (bovine serum albumin) capture rate with well time-resolved transport signals and excellent signal-to-noise ratio for the transport events. Also, a special mechanism involving transient process of ion redistribution inside the nanochannel is proposed to explain the unusual biphasic waveshapes of the current change induced by the protein transport.
Co-reporter:Qian Sheng, Yanbo Xie, Jun Li, Xinwei Wang and Jianming Xue
Chemical Communications 2017 - vol. 53(Issue 45) pp:NaN6127-6127
Publication Date(Web):2017/05/12
DOI:10.1039/C7CC01047H
Synthetic conical nanochannels have gained attention for their ion rectification behavior, which can be used to mimic the functionalities of biological ion channels. Employing these nanochannels and inspired by biological synaptic dynamics, we herein demonstrate a new nanofluidic device as a memristor, the ion transport conductance of which depends on the history of its ion flow. The nanofluidic memristors show excellent repeatability, high ON/OFF ratios, and sufficiently long retention times, which are highly desirable for logic control and neuromorphic engineering applications in nanofluidic systems as well as for fundamental transport studies of ionic liquids on a nanoscale.
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