查看更多>>摘要：? 2022 Elsevier B.V.Improving the efficiency of photocatalytic water splitting hydrogen production of iron-containing metal oxide photocatalysts is still a huge challenge. Herein, the new application of K2Fe4O7 for photocatalytic hydrogen production was proposed, and its photocatalytic performance was studied. Moreover, NiO was loaded on the surface of the K2Fe4O7, and improved the photocatalytic performance of K2Fe4O7. To understand the reason for the performance improvement, electrochemical impedance spectra, Surface photovoltage (SPV) and Transient photovoltage (TPV) were used to investigate the photogenerated carrier transportation mechanism of the samples. The result shows that the excellent photocatalytic performance of the samples was mainly due to the photogenerated electrons of K2Fe4O7 transferred to NiO, which enhanced the separation and transport of photogenerated carriers.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the effect of Ti addition on microstructure and corrosion properties of high entropy CoCuFeNiMnTix (x = 0.0–0.5) produced by the vacuum arc melting method was investigated. According to X-ray diffraction analysis, it has been found that Ti-free CoCuFeNiMn and CoCuFeNiMnTix HEAs had FCC crystal structures. It was understood from the SEM images that the CoCuFeNiMn and CoCuFeNiMnTix alloys were dendritically solidified. While the CoCuFeNiMn alloy had a homogeneous chemical composition in dendritic and interdendritic regions, Ti-rich regions were formed in the interdendritic regions with the Ti addition to the CoCuFeNiMn. The ratio of the Ti-rich region formed in the interdendritic region increased with the increase of Ti in the CoCuFeNiMnTix alloy. The corrosion resistance of the CoCuFeNiMnTix alloy decreased with the increase of Ti addition. The Ecorr and icorr values for CoCuFeNiMn alloy were found to be as ?0.322 V (vs. Ag/AgCl) and 6.30 × 10?7 A.cm?2, and these values were measured as ?0.982 V and 1.16 × 10?3 A.cm?2 for CoCuFeNiMnTi0.5 alloy, respectively. From the Nyquist and phase angle plots, it was understood that the 0.3% Ti ratio was the critical value for the formation of the passive TiO2 layer on the alloy surface. Ti addition's most important effect on the CoCuFeNiMn alloy's corrosion properties was determined as the transformation of pitting corrosion type to galvanic corrosion.
查看更多>>摘要：? 2022 Elsevier B.V.Multicomponent high entropy carbide ceramics (HECCs) have drawn increasing attention because of their potential applications as ultra-high temperature and super-hard materials. In this work, the stability, mixing behavior, mechanical, and temperature-dependent properties of rock-salt (TiZrHfTaM)C (M = Nb, Mo, W, V, or Cr) HECCs were first systematically investigated by density functional theory (DFT) and Debye-Grüneisen model methods. The five HECCs are thermodynamically stable owing to the negative formation enthalpies and cohesive energies. They could form the single-phase high entropy solid solution ceramics, owing to the evaluation of atom size and lattice differences, as well as mixing enthalpy criteria. Except for the system containing Cr, the others have already been confirmed by experimental findings. Among these, (TiZrHfTaNb)C most readily forms homogeneous solid solution phase, and is the most stable, brittlest, and hardest HECC material. Significantly, (TiZrHfTaV)C behaves slightly better than (TiZrHfTaNb)C with increasing temperature, owing to the comparable bulk modulus and Debye temperature, smaller volumetric expansion, and lower anharmonic effects. This work provides the instructive information for predicting and designing the high-performance ultra-high temperature ceramic materials applicable in extreme environments.
查看更多>>摘要：? 2022 Elsevier B.V.Typically, the high electrochemical performance of cathode materials is achieved by fine-tuning the surface morphology and particle size of the nano-electrode materials. Two-dimensional (2D) nanomaterials like nanoplates show astounding advantages of high surface area and shorter diffusion path-length, inducing improved Li-ion kinetics compared to bulk and 1D cathodes. This study reports the fabrication of 2D-nanoplates of LiMn1.5Ni0.5O4 via the solid-state method using α-MnO2 nanorods prepared from EMD, as a highly stable and long-cycle life cathode for lithium-ion battery (LIBs) applications. The fabricated 2D-LMNO nanoplates delivered an exceptional specific capacity of 88 mAh g?1 at a high current rate of 1 C and 98% retention of its initial capacity upon 1000 consecutive cycles. The nanoplates rendered a specific capacity of 77 mAh g?1 even at a high current rate of 7 C. The aligned LMNO stacked nanoplates with exposed {111} facets, and large Mn4+ concentration revealed high lithium-ion coefficient, decreased Mn dissolution, and high interfacial stability, which resulted in enhanced cycle stability and rate capability. The remarkable electrochemical performance of the LMNO cathode was attributed to its unique 2D-nanoplates structure, which is favourable for accommodating volume changes during the repeated insertion and de-insertion of lithium ions.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, we studied the switching mechanisms of Ni/SiOx/ITO devices before and after experiencing a reversible switching. And we also investigated its application for neuromorphic computing systems. First, we checked the composition of the device and progressed the electrical measurements. The device had two operating properties that are affected by an external applied voltage, and thus, we divided it into two distinct I-V curves to experimentally investigate the features. Even if they originated from the same RRAM devices, they exhibited different electrical measurements such as a retention, threshold voltages, and the conductance ratio. The I-V curve with an abrupt switching showed a good retention time of 7000 s and a wide conductance ratio of about ~41. On the other hand, the other I-V curve that shows progressive operation displayed a low retention time of 5000 s and a narrow conductance ratio of about ~3.43. We discussed the different results that were identified on the same device and concluded that it was caused by a change of switching mechanisms induced by a reversible switching in negative polarity. The overshoot current and large fluctuation in threshold voltage were used as evidence for our discussions. After identifying the electrical features, we progressed the biological processes such as potentiation/depression, paired-pulse facilitation (PPF) and spike-timing-dependent plasticity (STDP) to implement the neural networks.
查看更多>>摘要：? 2022 Elsevier B.V.A CuO/ZnO (C/Z) bilayer thin film was fabricated with a porous top CuO layer to facilitate a sensitive and selective response towards CO2 gas. Such a sensor architecture allowed optimum oxygen and CO2 gas adsorption in the interfacial region. The C/Z thin-film sensor exhibited a good response (47%) for 2500 ppm CO2 at 375 °C as opposed to CuO (15%) at 300 °C and ZnO (16%) at 350 °C. The sensor was selective to CO2 in respect of CO and CH4 gases at 375 °C with selectivity factor κCO2 ～ 5 and ～ 8 for CO and CH4 respectively. By analyzing the conductance-time transients for the gas, the adsorption behavior of CO2 on the heterogenous C/Z bilayer thin-film sensor was established. CO2 obeyed an extended Freundlich model of adsorption. Theoretical analysis of the said adsorption model was performed through which the activation energy (EA) and heat of adsorption (Q) of CO2 gas were estimated. A complementary relationship between EA and Q was established. It was shown that EA decreases with increasing concentration from 123.95 to 108.36 kJ/mol for 1000–2500 ppm CO2 for energetically heterogeneous surfaces. Alternatively, Q values increase with increasing concentration from 59.73 to 71.65 kJ/mol for 500–2500 ppm CO2. The CO2 sensing mechanism was elucidated based on surface defects for CuO and ZnO. CO2 sensing in the C/Z bilayer thin-film sensor was controlled by the adsorption of oxygen forming a space charge layer at the surface and interface of the p-n heterojunction and by band-bending as a result of the change of electron concentration across the junction.
查看更多>>摘要：? 2022 Elsevier B.V.Artificial photonic synapse devices (PSDs) hold great promise for the realization of next-generation artificial vision systems and processing units through a synergistic combination of brain-inspired neuromorphic computing and high levels of parallelism. Here, we demonstrate artificial PSDs based on solution-processed In-Sn-Zn-O (indium-tin-zinc oxide, ITZO) thin films capable of mimicking various neuromorphic functions. In particular, a transistor structure was adopted for PSDs to enable a facile control of the photo-response characteristics by gate biasing. With optimized gate bias condition, enhanced electrical conductance modulation was possible which can improve the energy efficiency of PSDs. In addition, we investigated the dependency of photo-response characteristics on light pulse waveforms to find out the correlation between various pulse parameters and the photo-current generation. Based on these findings, we demonstrated the emulation of associative learning which is one of the important cognitive functions of the brain. Moreover, to verify the translation of optically derived synaptic behaviors of ITZO PSDs into artificial neuromorphic computing, pattern recognition of handwritten digit patterns was demonstrated showing an accuracy up to 90.3%.
查看更多>>摘要：? 2022 Elsevier B.V.The development of efficient non-precious-metal catalysts for oxygen reduction reaction (ORR) is greatly important for accelerating the commercial application of fuel cells. Herein, polystyrene (PS) nanospheres are used as templates for the growth of zeolitic imidazolate framework (ZIF) complex precursors with variable molar ratios of Fe3+ to Zn2+ in situ. Through carbonization at a high temperature, the hierarchical porous carbon (HPC) materials with different proportions (xFeyZn-HPC, x + y = 100) have been prepared. The typical product 5Fe95Zn-HPC is composed of nitrogen (N)-doped hierarchical porous carbon loaded with Fe/Fe5C2 nanoparticles obtained at optimal molar ratio. As an electrocatalyst, the 5Fe95Zn-HPC shows a positive onset potential of 0.92 V (vs. RHE), half-wave potential of 0.77 V (vs. RHE) and limiting current density of 5.60 mA cm?2 at 0.055 V (vs. RHE). The hydrogen peroxide yield is less than 4.2%, and the electron transfer numbers are between 3.91 and 3.99 at 0.055 V~1.055 V in the catalytic ORR, which indicate that the reaction is dominated by four-electron reduction. The 5Fe95Zn-HPC has higher stability and methyl alcohol resistance in alkaline and acidic solutions. The above results indicate the excellent catalytic ORR performance of the 5Fe95Zn-HPC, almost as the commercial Pt/C. Additionally, 5Fe95Zn-HPC has the capacity to catalyze oxygen evolution reaction (OER) and adsorb methylene blue pollutants. Therefore, this work provides a practical method to design the hierarchical porous carbon-based material with outstanding multi-functions.
查看更多>>摘要：? 2022 Elsevier B.V.The aim of these comments is to bring attention of the scientific community to significant errors reported in the commented paper. The authors of the commented paper claimed the preparation of solid solutions Bi1?xHoxFeO3 with x = 0, 0.2, 0.4, 0.6, and 0.8. The obtained samples have been intensively characterized by different methods. However, the reported X-ray diffraction data unambiguously showed that single-phase solid solutions Bi1?xHoxFeO3 have not been obtained, and mixtures of other phases have been studied.
查看更多>>摘要：? 2022 Elsevier B.V.This paper reports the performance improvement of heterojunction channel field-effect transistor using an atomic-layer-deposited InGaZnO (IGZO) channel on basis of a band alignment. The heterojunction stack consisted of a 5 nm-thick In0.61Ga0.16Zn0.23O confinement layer (CL) and a 2 nm-thick In0.52Ga0.32Zn0.15O barrier layer (BL). Band-gap engineering through cation composition and thickness modulation of each layers allowed free electron diffusion from the In0.52Ga0.32Zn0.15O BL to the In0.61Ga0.16Zn0.23O CL and carriers confinement in CL, leading to the improvement in field-effect mobility. The control transistor with 5 nm-thick IGZO CL layer had a mobility of 33.4 cm2/Vs, whereas the heterojunction transistor with 2 nm-thick IGZO BL exhibited a higher mobility of 50.7 cm2/Vs as well as low gate swing of 89 mV/decade as a result of carrier transporting boosting. Moreover, the corresponding heterojunction channel transistors exhibited better gate bias stability due to the mitigation of gap states creation and passivating behavior by introducing the 2 nm-thick IGZO BL.
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