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Single atom catalysts exhibit particularly high catalytic activities in contrast to regular nanomaterial-based catalysts. Until recently, research has been mostly focused on single atom catalysts, and it remains a great challenge to synthesize bimetallic dimer structures. Herein, we successfully prepare high-quality one-to-one A-B bimetallic dimer structures (Pt-Ru dimers) through an atomic layer deposition (ALD) process. The Pt-Ru dimers show much higher hydrogen evolution activity (more than 50 times) and excellent stability compared to commercial Pt/C catalysts. X-ray absorption spectroscopy indicates that the Pt-Ru dimers structure model contains one Pt-Ru bonding configuration. First principle calculations reveal that the Pt-Ru dimer generates a synergy effect by modulating the electronic structure, which results in the enhanced hydrogen evolution activity. This work paves the way for the rational design of bimetallic dimers with good activity and stability, which have a great potential to be applied in various catalytic reactions., Atomically precise control over elemental distributions presents a challenge in the preparation of catalytic nanomaterials. Here the authors report Pt-Ru bimetallic dimer structures through atomic layer deposition process and identify the roles of Pt and Ru in hydrogen evolution reaction.

Pt single-atom catalysts are receiving more and more attention due to their different properties compared with nanostructures. As one typical kind of single-atom catalysts, Pt-based single-atom all...

Glycerol partial electrooxidation was studied on NixPd1–x (x = 100, 95, 90, and 80 atom %) nanoparticles synthesized using a polyol method. The shape-controlled urchin-like monometallic Ni and sphe...

Decreasing Pt loading in the anode layer below ∼0.025 mg·cm–2 is found to reduce the hydrogen oxidation reaction rate during polymer electrolyte membrane fuel cells (PEMFCs) normal operation, when using conventional Pt/C catalysts and electrode coating methods. To achieve extremely low Pt loading in the anode catalyst layer while maintaining high PEMFC performance and durability, a series of membrane electrode assemblies (MEAs) with low Pt loading in the anode layer are successfully prepared using an atomic layer deposition (ALD) technique. When the ALD cycle number is controlled, the Pt nanoparticles (NPs) with different sizes and loadings are directly deposited on the carbon layer to form the anode catalyst layer. The ALDPt NPs with uniform particle sizes are highly distributed on the carbon surface, which promotes the ALDPt with high electrochemical active surface area and enables enhanced performance of ALDPt-MEAs. Particularly, the 50ALDPt-MEA with the anode Pt prepared by 50ALD cycles shows excellen...

Configuring metal single-atom catalysts (SACs) with high electrocatalytic activity and stability is one efficient strategy in achieving the cost-competitive catalyst for fuel cells' applications. Herein, the atomic layer deposition (ALD) strategy for synthesis of Pt SACs on the metal-organic framework (MOF)-derived N-doped carbon (NC) is proposed. Through adjusting the ALD exposure time of the Pt precursor, the size-controlled Pt catalysts, from Pt single atoms to subclusters and nanoparticles, are prepared on MOF-NC support. X-ray absorption fine structure spectra determine the increased electron vacancy in Pt SACs and indicate the Pt-N coordination in the as-prepared Pt SACs. Benefiting from the low-coordination environment and anchoring interaction between Pt atoms and nitrogen-doping sites from MOF-NC support, the Pt SACs deliver an enhanced activity and stability with 6.5 times higher mass activity than that of Pt nanoparticle catalysts in boosting the oxygen reduction reaction (ORR). Density functional theory calculations indicate that Pt single atoms prefer to be anchored by the pyridinic N-doped carbon sites. Importantly, it is revealed that the electronic structure of Pt SAs can be adjusted by adsorption of hydroxyl and oxygen, which greatly lowers free energy change for the rate-determining step and enhances the activity of Pt SACs toward the ORR.

The dissolution of transition metal ions from positive electrodes and loss of (both electroactive and transport) Li+ ions seriously impair the durability of lithium ion batteries. We show herein that the improvement in the cycle life of lithium manganate spinel-graphite cells effected by multifunctional separators results from smaller interfacial resistances at both positive and negative electrodes, that can in turn be traced back to thinner, more uniform, and chemically different surface films, due to lessened parasitic reactions and a decreased accumulation of parasitic reaction products at electrode surfaces, as evidenced by HR-SEM, FIB-SEM, EDX, 19F MAS NMR, and ICP-OES data.

Lithium-rich layered oxides are promising cathode candidates because of their exceptional high capacity. The commercial application of these high-energy cathodes, however, is thwarted by the undesired rapid performance decay during cycling. Surface degradation has been widely considered to correlate with the performance decay of the cathodes, whereas, in this work, we demonstrate that the degradation of Li-rich high-energy Li1.2Ni0.13Mn0.54Co0.13O2 (HENMC) cathode material not only takes place at surfaces but also proceeds from its internal structure. In addition to demonstrating the surface reconstruction and the formation of a cathode–electrolyte interphase (CEI) layer of cycled HENMC cathode, this study uncovers the irreversible bulk phase transition from a Li-excess monoclinic (C2/m) solid solution into a conventional “layered” (R3m) phase, accompanied by complete loss of Li+ from the TM layers during cycling. Furthermore, the internal grains of HENMC bear lattice distortions, leading to the formatio...

Nowadays, lithium-ion batteries (LIBs) have been widely used in the automotive industry as power sources for electric vehicles (EVs). Nevertheless, the rapid development of EVs requires LIBs to enable higher energy density, enhanced safety, lower cost and longer cycle life. Ni-rich LiNixMnyCo1-x-yO2 (NMC) layered oxides have attracted great attention due to their high specific capacity (≈ 200 mAh/g), which are promising cathode materials for high-energy-density LIBs. The capability of high-voltage operation of the cathode can largely influence the energy density of LIB. Whereas, it is reported that Ni-rich cathode materials are unstable at high-voltage cycling conditions, leading to severe performance deterioration. (1, 2) Attempts have been made in developing synthesis and modification methods of Ni-rich cathode materials in order to improve their high-voltage performance.(3, 4) However, the design of better materials relies intensively on the deep understanding of the cycling behavior of cathode. There are a few studies looking into the degradation process of Ni-rich cathodes upon high-voltage cycling. Most of the work mainly focuses on investigating structural changes of the active material, for example, phase transformation at the surface,(2) crack generation within active particles.(5) Whereas, less attention was paid to the evolutions within the whole electrode. Herein, we study the cycling behavior of LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode at high cut-off voltages and look into the structural evolutions of cathode. In this work, Ni-rich NMC811 cathodes were cycled at different upper cut-off voltages to investigate their charge-discharge behavior under high-voltage cycling conditions. The NMC811 cathodes were assembled into coin cells with Li foil as counter electrode. The cells were cycled under different upper cut-off voltages of 4.3V, 4.6V and 4.8V with a C/10 cycling rate. Electrochemical impedance spectroscopy (EIS) measurements were conducted to analyze the ionic conduction and charge transfer at the electrolyte/particle interface of coin cells cycled at different cut-off voltages. The microstructure of pristine and cycled NMC811 cathodes were characterized in order to understand the structural evolution among different phases during high-voltage cycling. Our results show that high cut-off voltages have a negative influence on cell performance. The specific capacity of the cells cycled at 4.6V upper cut-off voltage showed a faster decrease compared to the 4.3V cells. In addition, more severe voltage decay is observed from cells cycled at 3.0V-4.6V. Whereas, when increasing the upper cut-off voltage from 4.6V to 4.8V, the cells exhibited less pronounced voltage decay, comparing to the difference observed between 4.3V and 4.6V cells. Significant increases in the charge transfer resistance (Rct) of cells cycling under higher voltages were observed from EIS measurements, which may indicate an elevated irreversible phase transformation of the active materials under high voltage cycling.(2) The microstructural evolution of NMC811 cathodes were observed under higher cycling voltages which could contribute to the poor performance of the high-voltage cells. The different behaviors of NMC811 cathode at high-voltages were analyzed in order to understand the degradation mechanisms of NMC811 cathodes under increasing cycling voltages. References: J. Li, L. E. Downie, L. Ma, W. Qiu and J. R. Dahn, Journal of The Electrochemical Society, 162, A1401 (2015). S.-K. Jung, H. Gwon, J. Hong, K.-Y. Park, D.-H. Seo, H. Kim, J. Hyun, W. Yang and K. Kang, Advanced Energy Materials, 4 (2014). X. Dong, J. Yao, W. Zhu, X. Huang, X. Kuai, J. Tang, X. Li, S. Dai, L. Shen, R. Yang, L. Gao and J. Zhao, Journal of Materials Chemistry A, 7, 20262 (2019). J. Zhang, J. Zhang, X. Ou, C. Wang, C. Peng and B. Zhang, ACS Appl Mater Interfaces, 11, 15507 (2019). Y. Mao, X. Wang, S. Xia, K. Zhang, C. Wei, S. Bak, Z. Shadike, X. Liu, Y. Yang, R. Xu, P. Pianetta, S. Ermon, E. Stavitski, K. Zhao, Z. Xu, F. Lin, X. Q. Yang, E. Hu and Y. Liu, Advanced Functional Materials, 29 (2019).

Indium (In) doped zinc oxide (ZnO) nanowires-gated AlGaAs/GaAs high electron mobility transistor (HEMT) was demonstrated for the detection of lactic acid. The In-doped ZnO nanowires were synthesized via chemical vapor deposition (CVD) method. Such In-doped ZnO nanowires offered an effective surface area with high surface area-to-volume ratio as well as a favorable environment for the immobilization of lactate oxidase (LOX) on the HEMT gate area. The In-doped ZnO nanowires have better conductivity than pure ZnO nanowires and retained the electroactivity of enzymes. Due to the novel structure of the Si-doped GaAs cap layer, the drain–source current of the AlGaAs/GaAs HEMT sensor showed a rapid response when lactic acid solutions at various concentrations were introduced to the gate area of the HEMT. The fabricated sensor exhibited a wide detection range from 3 pM to 3 mM and a low detection limit of 3 pM. The result indicated that a portable, fast response and high sensitivity lactic acid detector can be realized by AlGaAs/GaAs HEMT sensor.

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A ZnO nanowire (NW) array ultraviolet photodetector (PD) with Pt Schottky contacts has been fabricated on a glass substrate. Under UV light illumination, this PD showed a high photo-to-dark current ratio of 892 at 30 V bias. Interestingly, it was also found that this PD had a high sensitivity of 475 without external bias. This phenomenon could be explained by the asymmetric Schottky barrier height (SBH) at the two ends causing different separation efficiency of photogenerated electron–hole pairs, which resulted in the formation of photocurrent. It is anticipated to have potential applications in self-powered UV detection field.

In this paper, we aim to discover the mechanics-related novel phenomena on high-quality ZnO microwires through nanoindentation method. The mechanical property parameters of ZnO microwires were determined and a distinctive creep damage phenomenon was revealed. By using the cycles load mode in the nanoindentation experiments, the indentation size effect was demonstrated to exist in the ZnO microwires: the elastic modulus ranged from 65.9 GPa to 12.3 GPa and the hardness changed from 11.1 GPa to 1.8 GPa with the increase of indentation depth. Furthermore, the indentation-induced mechanical and electrical damage caused a permanent plastic deformation and an increase of 41% in the longitudinal conductance of the ZnO microwires.

The synergistic scale inhibition effect of rare-earth permanent magnetic material and polyaspartic acid is studied. The performance of synergistic scale inhibition is studied in different magnetic field intensity, water hardness and rate of concentration. Static and dynamic scale inhibition tests show that the two water treatment ways have good synergistic scale inhibition effect. The scale inhibition performance of polyaspartic acid can be increased greatly by the magnetization of water.

Polyaspartic acid (PASP) composite material, a scale and corrosion inhibitor, is prepared from PASP, acrylic acid-acrylic ester- itaconic acid tripolymer (IA-AA-AE) and 2-phosphonobutane- 1,2,4-tricarboxylic acid (PBTCA). The scale inhibition effects of PASP and PASP composite are investigated. Calcium carbonate crystals in scale samples are characterized by means of SEM. Experimental results show that the scale inhibition rate can reach 98.7 % and corrosion inhibition rate 96.5 % under the conditions of Ca2+ 639 mg.L-1 and PASP composite material 40 mg.L-1. SEM results show that calcite and aragonite can be transformed into vaterite completely by using PASP composite material.

A novel two-step surface modification method that includes atomic layer deposition (ALD) of TiO2 followed by post-annealing treatment on spinel LiNi0.5 Mn1.5 O4 (LNMO) cathode material is developed to optimize the performance. The performance improvement can be attributed to the formation of a TiMn2 O4 (TMO)-like spinel phase resulting from the reaction of TiO2 with the surface LNMO. The Ti incorporation into the tetrahedral sites helps to combat the impedance growth that stems from continuous irreversible structural transition. The TMO-like spinel phase also alleviates the electrolyte decomposition during electrochemical cycling. 25 ALD cycles of TiO2 growth are found to be the optimized parameter toward capacity, Coulombic efficiency, stability, and rate capability enhancement. A detailed understanding of this surface modification mechanism has been demonstrated. This work provides a new insight into the atomic-scale surface structural modification using ALD and post-treatment, which is of great importance for the future design of cathode materials.

An excellent biosensor with ZnO nanowires-gated AlGaAs/GaAs high electron mobility transistor (HEMT) was used to detect lactic acid. Due to the new structure, addition of the Si-doped GaAs cap layer, the HEMT biosensor could detect a wide range of lactic acid concentrations from 0.03 nM to 300 mM. The novel biosensor exhibiting good performance along with fast response, high sensitivity, wide detection range, and long-term stability, can be integrated with a commercially available transmitter to realize lactic acid detection.