As a new generation electrode materials for energy storage, perovskites have attracted wide attention because of their unique crystal structure, reversible active sites, rich oxygen vacancies, and good stability. In this review, the design and engineering progress of perovskite materials for supercapacitors (SCs) in recent years is summarized. Specifically, the review will focus on four types of perovskites, perovskite oxides, halide perovskites, fluoride perovskites, and multi-perovskites, within the context of their intrinsic structure and corresponding electrochemical performance. A series of experimental variables, such as synthesis, crystal structure, and electrochemical reaction mechanism, will be carefully analyzed by combining various advanced characterization techniques and theoretical calculations. The applications of these materials as electrodes are then featured for various SCs. Finally, we look forward to the prospects and challenges of perovskite-type SCs electrodes, as well as the future research direction. 

Emerging perovskite materials for supercapacitors: Structure, synthesis, modification, advanced characterization, theoretical calculation and electrochemical performance

Planar semiconductor InGaAs/InP single photon avalanche diodes with high responsivity and low dark count rate are preferred single photon detectors in near-infrared communication. However, even with well-designed structures and well-controlled operational conditions, the performance of InGaAs/InP SPADs is limited by the inherent characteristics of avalanche process and the growth quality of InGaAs/InP materials. It is difficult to ensure high detection efficiency while the dark count rate is controlled within a certain range at present. In this paper, we fabricated a device with a thick InGaAs absorption region and an anti-reflection layer. The quantum efficiency of this device reaches 83.2%. We characterized the single-photon performance of the device by a quenching circuit consisting of parallel-balanced InGaAs/InP single photon detectors and single-period sinusoidal pulse gating. The spike pulse caused by the capacitance effect of the device is eliminated by using the characteristics of parallel balanced common mode signal elimination, and the detection of small avalanche pulse amplitude signal is realized. The maximum detection efficiency is 55.4% with a dark count rate of 43.8 kHz and a noise equivalent power of 6.96 × 10−17 W/Hz1/2 at 247 K. Compared with other reported detectors, this SPAD exhibits higher SPDE and lower noise-equivalent power at a higher cooling temperature.

High photon detection efficiency InGaAs/InP single photon avalanche diode at 250 K

Ultra-high energy density battery-type materials are promising candidates for supercapacitors (SCs); however, slow ion kinetics and significant volume expansion remain major barriers to their practical applications. To address these issues, hierarchical lattice distorted α-/γ-MnS@Cox Sy core-shell heterostructure constrained in the sulphur (S), nitrogen (N) co-doped carbon (C) metal-organic frameworks (MOFs) derived nanosheets (α-/γ-MnS@Cox Sy @N, SC) have been developed. The coordination bonding among Cox Sy , and α-/γ-MnS nanoparticles at the interfaces and the π-π stacking interactions developed across α-/γ-MnS@Cox Sy and N, SC restrict volume expansion during cycling. Furthermore, the porous lattice distorted heteroatom-enriched nanosheets contain a sufficient number of active sites to allow for efficient electron transportation. Density functional theory (DFT) confirms the significant change in electronic states caused by heteroatom doping and the formation of core-shell structures, which provide more accessible species with excellent interlayer and interparticle conductivity, resulting in increased electrical conductivity. . The α-/γ-MnS@Cox Sy @N, SC electrode exhibits an excellent specific capacity of 277 mA hg-1 and cycling stability over 23 600 cycles. A quasi-solid-state flexible extrinsic pseudocapacitor (QFEPs) assembled using layer-by-layer deposited multi-walled carbon nanotube/Ti3 C2 TX nanocomposite negative electrode. QFEPs deliver specific energy of 64.8 Wh kg-1 (1.62 mWh cm-3 ) at a power of 933 W kg-1 and 92% capacitance retention over 5000 cycles.

Electronic Structure Engineered Heteroatom Doped All Transition Metal Sulfide Carbon Confined Heterostructure for Extrinsic Pseudocapacitor.

The hydrogen recirculation ejector plays a pivotal role in proton exchange membrane fuel cell systems. Nevertheless, a comprehensive grasp of the intricate two-phase flow characteristics within hydrogen recirculation ejectors remains elusive. This investigation delves into the condensation and droplet behaviors of an ejector designed for a 100 kW fuel cell stack. The analysis relies on a two-phase flow model that takes into account both homogeneous and heterogeneous condensation. The findings reveal that homogeneous condensation nuclei manifest within the mixing chamber when the stack power surpasses 31 kW. The average median diameter of homogeneous droplets at the ejector outlet measures 0.367 μm, whereas that of heterogeneous droplets stands at 1.265 μm, signifying a 26.5 % augmentation compared to their initial size. Additionally, two crucial factors impact droplet size: residence time and subcooling degree. At the 100 kW condition, the droplet residence time is a mere 0.272 ms, yielding a meager droplet flow rate of merely 1.79 mg/s. In contrast, at the 53 kW condition, the downstream of the mixing chamber exhibits the maximum subcooling degree, resulting in the maximum droplet flow rate of 22.12 mg/s. A temperature elevation of 2.68 K at the ejector outlet is observed due to the latent heat of condensation. Furthermore, condensation has a marginal impact on the entrainment ratio, with the most significant reduction being 4.18 %, averaging at 1.42 %. 

Condensation and droplet characteristics in hydrogen recirculation ejectors for PEM fuel cell systems

Ternary transition metal nitrides are emerging pseudocapacitive materials for the development of high-energy-density flexible supercapacitors. The present report demonstrates a facile, scalable, and binderless fabrication of unique nickel molybdenum nitride (Ni-Mo-N) nanocomposite directly on stainless-steel mesh (SSM) via reactive magnetron cosputtering technology for flexible symmetric supercapacitor (FSSC) application. Benefiting from the advanced synergism between multiple integrated phases, the ternary Ni-Mo-N/SSM electrode exhibits highly pseudocapacitive characteristics and delivers a maximum specific capacitance of ∼43.11 mF cm–2 in comparison to pristine Ni3N/SSM (∼2.32 mF cm–2) and Mo2N/SSM (∼34.94 mF cm–2) electrodes. An extensive b-value and Dunn's investigation reveal the dominance of surface-limited capacitive and pseudocapacitive mechanisms over diffusion-limited redox processes at the Ni-Mo-N nanocomposite. The as-assembled FSSC device (Ni-Mo-N/SSM||Ni-Mo-N/SSM) attains an impressive cell capacitance of ∼37.89 mF cm–2 (or 229.64 F g–1) at 0.15 mA cm–2 together with remarkable cycling performance, retaining ∼95.12% capacitance after 10,000 continuous galvanostatic charge–discharge (GCD) cycles. Moreover, the FSSC renders a superior combination of high energy, ∼4.26 μWh cm–2 (or 25.83 Wh kg–1), and power density, ∼1.07 mW cm–2 (or 6.50 kW kg–1), while displaying state-of-the-art stable flexibility, maintaining ∼95.3% and ∼94.5% capacitance after 1500 GCD cycles at +90 and −90° bending angles, respectively. Therefore, the current fabrication strategy of reactively cosputtering a Ni-Mo-N nanocomposite presents a promising avenue for developing high-energy-density and ultrastable flexible supercapacitors. 

Pseudocapacitance Powered Nickel Molybdenum Nitride Nanocomposite Reactively Cosputtered on Stainless-Steel Mesh toward Advanced Flexible Supercapacitors

Origin of superior pseudocapacitive mechanism of transition metal nitrides

Transient numerical study of CO2 two-phase flow in a needle adjustable ejector

In this study, the influence of laser energy and pressure on propulsion performance of zinc and acrylonitrile butadiene styrene (ABS) is investigated by impulse measurement, fast exposure images, spectral diagnostics and target ablation. A Q-switched Nd:YAG laser with the wavelength of 1064 nm and pulse width of 6 ns is employed. The impulse and coupling coefficient generated by laser ablation ABS are greater than that of Zn, and they exhibit a similar variation trend with pressure. However, at higher pressure levels, the change in impulse versus laser energy is not completely coincident between Zn and ABS samples. The target property plays a significant role in the generation and propagation of plume related to the plasma parameters such as electron density and temperature. The temporal evolution images indicate that the plasma plume of laser-induced Zn presents a faster decay in comparison with that of ABS, which is ascribed to the fact that the gas temperature of ABS is higher than the electron temperature of Zn plasma in the local thermodynamical equilibrium. Also, the electron density is lower for Zn due to the rapid heat diffusion and higher ablation threshold of metal. It is found that the surface absorption is dominant for metal because the ablated crater of Zn performs larger diameter and shallower depth. On the contrary, the shrinkage in diameter but enhancement in depth of crater is observed from ABS surface, and the ablation mass is larger, suggesting the obvious volume absorption for polymer. The results reveal that the target property can engender an important effect on the energy conversion between laser, target and plasma.

https://iopscience.iop.org/article/10.1088/1361-6463/acbe08/pdf

A comparative study on the characteristics of nanosecond laser ablation zinc and acrylonitrile butadiene styrene targets

http://www.cell.com/article/S2405844022018187/pdf

Numerical simulation of the magnetically gain-switched chemical oxygen-iodine laser

InGaAs/InP single-photon avalanche diodes have proven to be the most practical solution for quantum key distribution and long-distance 3-D imaging. In this paper, to further improve the device performance, a new reflector involving the metal layer and <inline-formula><tex-math notation="LaTeX">$S\mathrm{i}{O_2}$</tex-math></inline-formula>/<inline-formula><tex-math notation="LaTeX">$\text{Ti}{O_2}$</tex-math></inline-formula> distributed Bragg reflector has been applied together with a micro-lens to increase the absorption efficiency by 58%. The normalized dark count rate is 127 Hz, 361 Hz, and 665 Hz for 10%, 20%, 30% photon detection efficiency, respectively, when it is operated under the gated mode with a pulse repetition rate of 50 MHz and pulse width of 1 ns at 233 K temperature. The normalized dark count rate is nearly an order of magnitude lower than commercial devices at 233 K, reflecting the high performance of the proposed near-infrared single-photon detectors.

High Performance InGaAs/InP Single-Photon Avalanche Diode Using DBR-Metal Reflector and Backside Micro-Lens

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