In the past ten years, carbon dots-decorated, carbon-based, metal-free catalysts (CDs-C-MFCs) have become the fastest-growing branch in the metal-free materials for energy storage field. However, the further development of CDs-C-MFCs needs to clear up the electronic transmission mechanism rather than primarily relying on trial-and-error approaches. This review presents systematically and comprehensively for the first time the latest advances of CDs-C-MFCs in supercapacitors and metal-air batteries. The structure-performance relationship of these materials is carefully discussed. It is indicated that carbon dots (CDs) can act as the electron-rich regions in CDs-C-MFCs owing to their unique properties, such as quantum confinement effects, abundant defects, countless functional groups, etc. More importantly, specific doping can effectively modify the charge/spin distribution and then facilitate electron transfer. In addition, present challenges and future prospects of the CDs-C-MFCs are also given.
This review systematically summarizes the recent advances in two-dimensional nanomaterials for photocatalytic reduction of CO2 and its related mechanisms.
The commonly used planar phased array radar has a number of issues in making polarimetric measurements, including increase of beam width, sensitivity loss and polarization coupling. The Cylindrical Polarimetric Phased Array Radar (CPPAR) with commutating scan is proposed to avoid these deficiencies.
The construction of a heterojunction photocatalyst as an effective method to enhance the charge separation has attracted great attention from researchers. Herein, a novel BiVO4/self-assembled perylene diimide (BiVO4/PDIsa) organic supermolecule photocatalyst was successfully constructed via an in situ electrostatic assembling method. Various characterization methods were employed to systematically study the phase structure, morphology, and photoelectrochemical properties of BiVO4/PDIsa. Among the different ratios of composites, the 20%BiVO4/PDIsa exhibited the optimal photocatalytic activity under visible-light irradiation, and its degradation efficiency for tetracycline (TC) could reach 81.75% within 30 min. In addition, the corresponding TC degradation rate constant was 0.0545 min–1, which was 1.69 times and 3.61 times that of the pure PDIsa and BiVO4, respectively. Subsequently, the radical trapping experiments and electron spin response (ESR) test indicated that 1O2, •O2–, and h+ were the primary reactive species in the photocatalytic process. Importantly, the efficient electron migration path and photocatalytic mechanism of the catalyst were inferred by experimental study and density functional theory (DFT) calculations. In brief, this work provides a promising approach in designing an inorganic–organic Z-scheme heterojunction photocatalyst for environmental remediation.
β-Zn4Sb3 has one of the highest ZT reported for binary compounds, but its practical applications have been hindered by a reported poor stability. Here we report the fabrication of nearly dense single-phase β-Zn4Sb3 and a study of its thermoelectric transport coefficients across a wide temperature range. Around 425 K we find an abrupt decrease of its thermal conductivity. Past this point, Zn atoms can migrate from crystalline sites to interstitial positions; β-Zn4Sb3 becomes metastable and gradually decomposes into Zn(hcp) and ZnSb. However, above 565 K it recovers its stability; in fact, the damage caused by decomposition can be repaired completely. This is key to its excellent thermoelectric performance at high temperature: the maximum ZT reaches 1.4. Molecular dynamics simulations are used to shed light on the microscopic behavior of the material.
Abstract The quality of polarimetric radar data degrades as the signal-to-noise ratio (SNR) decreases. This substantially limits the usage of collected polarimetric radar data to high SNR regions. To improve data quality at low SNRs, multilag correlation estimators are introduced. The performance of the multilag estimators for spectral moments and polarimetric parameters is examined through a theoretical analysis and by the use of simulated data. The biases and standard deviations of the estimates are calculated and compared with those estimates obtained using the conventional method.
Abstract MXenes, an innovative class of two‐dimensional (2D) materials composed of transition‐metal carbides and/or nitrides, have garnered significant interest for their potential in energy storage and conversion applications, which is largely attributed to their modifiable surface terminations, exceptional conductivity, and favorable hydrophilic characteristics. MXenes show various ion transport behaviors in applications like electrochemical catalysis, supercapacitors, and batteries, encompassing processes like electrostatic adsorption of surface ions, redox reactions of ions, and interlayer ion shuttle. This review aims to present a summary of advancements in the comprehension of ion transport behaviors of Ti 3 C 2 T x MXenes. First, the composition, properties, and synthesis techniques of MXenes are concisely summarized. Subsequently, the discussion delves into the mechanisms of ion transport in MXenes during CO 2 reduction, water splitting, supercapacitor operation, and battery performance, elucidating the factors determining the electrochemical behaviors and efficacy. Furthermore, a compilation of strategies used to optimize ion transport behaviors in MXenes is presented. The article concludes by presenting the challenges and opportunities for these fields to facilitate the continued progress of MXenes in energy‐related technologies.
Abstract In order to study the current characteristics of corona discharge in high voltage transmission, the time-domain characteristics and volt ampere characteristics of corona discharge under different high voltage are tested and analyzed. The actual test results show that: in the whole process of corona discharge, with the increase of inter electrode voltage, the frequency of pulse current increases, and the duration of current remains unchanged; negative corona discharge is more likely to occur, and with the increase of voltage, the average current growth rate is higher than positive corona discharge. Under the same interelectrode voltage, the negative corona current is stronger than the positive one. The nonlinearity of equivalent resistance between positive corona discharge electrodes is stronger than that of negative corona discharge.
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