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991.
The discovery of stable and noble‐metal‐free catalysts toward efficient electrochemical reduction of nitrogen (N2) to ammonia (NH3) is highly desired and significantly critical for the earth nitrogen cycle. Here, based on the theoretical predictions, MoS2 is first utilized to catalyze the N2 reduction reaction (NRR) under room temperature and atmospheric pressure. Electrochemical tests reveal that such catalyst achieves a high Faradaic efficiency (1.17%) and NH3 yield (8.08 × 10?11 mol s?1 cm?1) at ?0.5 V versus reversible hydrogen electrode in 0.1 m Na2SO4. Even in acidic conditions, where strong hydrogen evolution reaction occurs, MoS2 is still active for the NRR. This work represents an important addition to the growing family of transition‐metal‐based catalysts with advanced performance in NRR.  相似文献   
992.
Using memristor crossbar arrays to accelerate computations is a promising approach to efficiently implement algorithms in deep neural networks. Early demonstrations, however, are limited to simulations or small‐scale problems primarily due to materials and device challenges that limit the size of the memristor crossbar arrays that can be reliably programmed to stable and analog values, which is the focus of the current work. High‐precision analog tuning and control of memristor cells across a 128 × 64 array is demonstrated, and the resulting vector matrix multiplication (VMM) computing precision is evaluated. Single‐layer neural network inference is performed in these arrays, and the performance compared to a digital approach is assessed. Memristor computing system used here reaches a VMM accuracy equivalent of 6 bits, and an 89.9% recognition accuracy is achieved for the 10k MNIST handwritten digit test set. Forecasts show that with integrated (on chip) and scaled memristors, a computational efficiency greater than 100 trillion operations per second per Watt is possible.  相似文献   
993.
Stem cells have attracted increasing research interest in the field of regenerative medicine because of their unique ability to differentiate into multiple cell lineages. However, controlling stem cell differentiation efficiently and improving the current destructive characterization methods for monitoring stem cell differentiation are the critical issues. To this end, multifunctional graphene–gold (Au) hybrid nanoelectrode arrays (NEAs) to: (i) investigate the effects of combinatorial physicochemical cues on stem cell differentiation, (ii) enhance stem cell differentiation efficiency through biophysical cues, and (iii) characterize stem cell differentiation in a nondestructive real‐time manner are developed. Through the synergistic effects of physiochemical properties of graphene and biophysical cues from nanoarrays, the graphene‐Au hybrid NEAs facilitate highly enhanced cell adhesion and spreading behaviors. In addition, by varying the dimensions of the graphene‐Au hybrid NEAs, improved stem cell differentiation efficiency, resulting from the increased focal adhesion signal, is shown. Furthermore, graphene‐Au hybrid NEAs are utilized to monitor osteogenic differentiation of stem cells electrochemically in a nondestructive real‐time manner. Collectively, it is believed the unique multifunctional graphene‐Au hybrid NEAs can significantly advance stem‐cell‐based biomedical applications.  相似文献   
994.
Porous Ni(OH)2 nanoflakes are directly grown on the surface of nickel foam supported Ni3Se2 nanowire arrays using an in situ growth procedure to form 3D Ni3Se2@Ni(OH)2 hybrid material. Owing to good conductivity of Ni3Se2, high specific capacitance of Ni(OH)2 and its unique architecture, the obtained Ni3Se2@Ni(OH)2 exhibits a high specific capacitance of 1689 µAh cm?2 (281.5 mAh g?1) at a discharge current of 3 mA cm?2 and a superior rate capability. Both the high energy density of 59.47 Wh kg?1 at a power density of 100.54 W kg?1 and remarkable cycling stability with only a 16.4% capacity loss after 10 000 cycles are demonstrated in an asymmetric supercapacitor cell comprising Ni3Se2@Ni(OH)2 as a positive electrode and activated carbon as a negative electrode. Furthermore, the cell achieved a high energy density of 50.9 Wh L?1 at a power density of 83.62 W L?1 in combination with an extraordinary coulombic efficiency of 97% and an energy efficiency of 88.36% at 5 mA cm?2 when activated carbon is replaced by metal hydride from a commercial NiMH battery. Excellent electrochemical performance indicates that Ni3Se2@Ni(OH)2 composite can become a promising electrode material for energy storage applications.  相似文献   
995.
Structure engineering of ultrathin metal–organic framework (MOF) nanosheets to self‐supporting and well‐aligned MOF superstructures is highly desired for diverse applications, especially important for electrocatalysis. In this work, a facile layered double hydroxides in situ transformation strategy is developed to synthesize ultrathin bimetal‐MOF nanosheets (BMNSs) arrays on conductive substrates. This approach is versatile, and applicable to obtain various BMNSs or even trimetal‐MOF nanosheets arrays on different substrates. As a proof of concept application, the obtained ultrathin NiCo‐BDC BMNSs array exhibits an excellent catalytic activity toward the oxygen evolution reaction with an overpotential of only 230 mV to reach a current density of 10 mA cm?2 in 1 m KOH. The present work demonstrates a strategy to prepare ultrathin bimetal‐MOF nanosheets arrays, which might open an avenue for various promising applications of MOF materials.  相似文献   
996.
Ultralow power chemical sensing is essential toward realizing the Internet of Things. However, electrically driven sensors must consume power to generate an electrical readout. Here, a different class of self‐powered chemical sensing platform based on unconventional photovoltaic heterojunctions consisting of a top graphene (Gr) layer in contact with underlying photoactive semiconductors including bulk silicon and layered transition metal dichalcogenides is proposed. Owing to the chemically tunable electrochemical potential of Gr, the built‐in potential at the junction is effectively modulated by absorbed gas molecules in a predictable manner depending on their redox characteristics. Such ability distinctive from bulk photovoltaic counterparts enables photovoltaic‐driven chemical sensing without electric power consumption. Furthermore, it is demonstrated that the hydrogen (H2) sensing properties are independent of the light intensity, but sensitive to the gas concentration down to the 1 ppm level at room temperature. These results present an innovative strategy to realize extremely energy‐efficient sensors, providing an important advancement for future ubiquitous sensing.  相似文献   
997.
The CO2 reduction reaction (CO2RR) driven by renewable electricity represents a promising strategy toward alleviating the energy shortage and environmental crisis facing humankind. Cu species, as one type of versatile electrocatalyst for the CO2RR, attract tremendous research interest. However, for C2 products, ethanol formation is commonly less favored over Cu electrocatalysts. Herein, AuCu alloy nanoparticle embedded Cu submicrocone arrays (AuCu/Cu‐SCA) are constructed as an active, selective, and robust electrocatalyst for the CO2RR. Enhanced selectivity for EtOH is gained, whose Faradaic efficiency (FE) reaches 29 ± 4%, while ethylene formation is relatively inhibited (16 ± 4%) in KHCO3 aqueous solution. The ratio between partial current densities of EtOH and C2H4 (jEtOH/jC2H4) can be tuned in the range from 0.15 ± 0.27 to 1.81 ± 0.55 by varying the Au content of the electrocatalysts. The combined experimental and theoretical calculation results identify the importance of Au in modifying binding energies of key intermediates, such as CH2CHO*, CH3CHO*, and CH3CH2O*, which consequently modify the activity and selectivity (jEtOH/jC2H4) for the CO2RR. Moreover, AuCu/Cu‐SCA also shows high durability with both the current density and FEEtOH being largely maintained for 24 h electrocatalysis.  相似文献   
998.
以风能和太阳能为代表的新能源具有随机性、间歇性和波动性,对新能源发电功率进行预测是有效解决以上问题的途径。在确定性预测中充分考虑风电出力和预测模型特性,提出分段支持向量机(piecewise support vector machine,PSVM)和神经网络(neural network,NN)预测算法;充分考虑天气特征对光伏出力的影响,提出基于气象特性分析的光伏出力预测算法。通过若干风电场的算例分析,证明了上述几种预测模型的实用性,为功率预测的可靠性分析提供支持。  相似文献   
999.
An ideal photoelectrochemical (PEC) anode should process effective light absorption, charge transport, and separation efficiency. Here, a novel 3D brochosomes‐like TiO2/WO3/BiVO4 array as an efficient photoanode by combining a colloid polystyrene sphere template and electrochemical deposition routes for PEC hydrogen generation is reported. The as‐fabricated 3D TiO2/WO3/BiVO4 brochosomes photoanode yields excellent PEC performance with photocurrent densities of ≈3.13 and ≈4.27 mA cm?2 with FeOOH/NiOOH catalyst, respectively, measured in 0.5 m Na2SO4 solution with 0.1 m Na2SO3 at 1.23 V versus reversible hydrogen electrode (RHE) under simulated AM1.5 light illumination, which is ≈6 times the reference sample of a planar WO3/BiVO4 film electrode. The significantly improved performance could be benefited from the ordered hollow porous structure that provides enhanced light absorption and efficient charge transport as well as improved charge separation efficiency by WO3/BiVO4 “host–guest” heterojunctions.  相似文献   
1000.
使用有机无机杂化钙钛矿材料作为光吸收层的钙钛矿太阳能电池自进入人们的视野以来,其制备工艺和器件结构不断得到优化,短短几年内效率取得了非常可观的增长。与此同时,这种基于三维钙钛矿材料的电池的缺点也越来越突出,尤其是材料的不稳定性,严重阻碍了其发展。低维钙钛矿材料具有有机胺层与无机层(金属卤化物钙钛矿晶体)之间相互交替的低维(层状)结构,其中被有机胺隔开的独立钙钛矿层中八面体的层数n越小,钙钛矿越接近二维结构。相比传统三维钙钛矿结构,低维钙钛矿材料应用于光伏器件具有两大优势:(1)耐湿性、光热稳定性大大增强;(2)可以通过改变n和插入的有机胺的种类来实现光学及电学性质的可调性。然而,低维钙钛矿具有较大的光学带隙,有机胺的引入降低了载流子迁移率,导致低维钙钛矿电池的效率明显低于三维钙钛矿电池。因此,近三年来除研究钙钛矿层数对材料性质和器件性能的影响外,研究者们主要从选择合适的有机胺和优化薄膜制备工艺方面不断尝试,并取得了丰硕的成果,在充分发挥低维钙钛矿稳定性优势的同时大幅提升了器件效率。目前,低维钙钛矿太阳能电池的光电转换效率已由2014年的4.37%跃升至13.7%。在较高效率的低维钙钛矿太阳能电池中已取得成功应用的有机胺类包括苯乙胺(PEA)、正丁胺(n-BA)、异丁胺(iso-BA)、聚乙烯亚胺(PEI)等。其中PEA应用得最早;n-BA是运用在目前为止最高效的低维钙钛矿电池中的有机胺;而PEI插层形成的低维钙钛矿拥有相对更小的光学带隙和更高的耐湿性,但载流子的传输会受到更大的限制。低维钙钛矿薄膜的制备起初主要采用简单的一步旋涂法,但此法所得的低维钙钛矿平行于基底生长,器件效率很低。近两年的研究工作将基底预热、浸泡、反溶剂滴加等手段引入到钙钛矿旋涂工艺中,实现了低维钙钛矿优先垂直基底生长,为突破低效率瓶颈提供了可能。此外,以三维钙钛矿为基础,以有机胺为添加剂,制得的二维和三维混合的钙钛矿结构,也可以实现器件效率和稳定性的双提升。本文归纳了低维钙钛矿光伏器件的研究进展,分别对低维钙钛矿的分子结构、插入的有机胺的选择、钙钛矿薄膜的制备方法等进行介绍,分析了低维钙钛矿太阳能电池面临的问题并展望其前景,以期为制备稳定和环境友好的新型钙钛矿太阳能电池提供参考。  相似文献   
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