Ultra-narrowband interference circuits enable low-noise and high-rate photon counting for InGaAs/InP avalanche photodiodes.

Afterpulsing noise in InGaAs/InP single photon avalanche photodiodes (APDs) is caused by carrier trapping and can be suppressed successfully through limiting the avalanche charge via sub-nanosecond gating. Detection of faint avalanches requires an electronic circuit that is able to effectively remove the gate-induced capacitive response while keeping photon signals intact. Here we demonstrate a novel ultra-narrowband interference circuit (UNIC) that can reject the capacitive response by up to 80 dB per stage with little distortion to avalanche signals. Cascading two UNIC's in a readout circuit, we were able to enable a high count rate of up to 700 MC/s and a low afterpulsing of 0.5 % at a detection efficiency of 25.3 % for 1.25 GHz sinusoidally gated InGaAs/InP APDs. At a temperature of -30 ∘C, we measured an afterpulsing probability of 1 % at a detection efficiency of 21.2 %.

Suppression of Adverse Phase Transition of Layered Oxide Cathode via Local Electronic Structure Regulation for High-Capacity Sodium-Ion Batteries.

Advancing the high-voltage stability of the O3-type layered cathodes for sodium-ion batteries is critical to boost their progress in energy storage applications. However, this type of cathode often suffers from intricate phase transition and structural degradation at high voltages (i.e., >4.0 V vs Na+/Na), resulting in rapid capacity decay. Here, we present a Li/Ti cosubstitution strategy to modify the electronic configuration of oxygen elements in the O3-type layered oxide cathode. This deliberate modulation simultaneously mitigates the phase transitions and counteracts the weakening of the shielding effect resulting from the extraction of sodium ions, thus enhancing the electrostatic bonding within the TM layer and inducing and optimizing the O3-OP2 phase transition occurring in the voltage range of 2.0-4.3 V. Consequently, the cosubstituted NaLi1/9Ni1/3Mn4/9Ti1/9O2 exhibits an astounding capacity of 161.2 mAh g-1 in the voltage range of 2.0-4.3 V at 1C, and stable cycling up to 100 cycles has been achieved. This work shows the impact mechanism of element substitution on interlayer forces and phase transitions, providing a crucial reference for the optimization of O3-type materials.

Strong morphological effect of Mn3O4 nanocrystallites on the catalytic activity of Mn3O4 and Au/Mn3O4 in benzene combustion.

Gold nanoparticles (3-4 nm) were deposited on Mn3O4 nanocrystallites with three distinct morphologies (cubic, hexagonal, and octahedral). The resulting structures were characterized, and their activities for benzene combustion were evaluated. The dominant exposed facets for the three kinds of Mn3O4 polyhedrons show the activity order: (103)≈(200)>(101). A similar activity order was derived for the interfaces between the Au and the Mn3O4 facet: Au/(200)≈Au/(103)>Au/(101). The metal-support interactions between the Au nanoclusters and specific facets of the Mn3O4 polyhedrons lead to a unique interfacial synergism in which the electronic modification of the Au nanoparticles and the morphology of the Mn3O4 substrate have a joint effect that is responsible for a significant enhancement in the catalytic activity of the Au/Mn3O4 system.

High-efficiency and durable V-Ti-Nb ternary catalyst prepared by a wet-solid mechanochemical method for sustainably producing acrylic acid via acetic acid-formaldehyde condensation.

Based on the precise phase control V species adjustment of vanadium phosphorus oxides (VPOs), a series of metal oxides (Nb2O5, MoO3, WO3, and Bi2O3) were selected as modification agents to further enhance the catalytic activity and retain the excellent durability of VPO-TiO2-based catalysts for the new procedure of producing acrylic acid via acetic acid-formaldehyde condensation. At an elevated liquid hourly space velocity (LHSV), the (AA + MA) selectivity reached 92.3% with a (MA + AA) formation rate of 63.8 µmol-1 gcat -1 min-1 over the Nb-decorated catalyst (catalyst VTi-Nb), and it maintained good durability for up to 100 h. The detailed characterization results of XRD, Raman, XPS, NH3-TPD, CO2-TPD, and H2-TPR, demonstrated that the addition of Nb2O5 could observably enhance the catalytic efficiency of the VPO-TiO2 catalyst. It not only improved the catalyst durability by enhancing prereduction of the V5+ species, but also enhanced the active site density to improve the catalytic activity.

High-Performance NixCo3-xO4/Ti3C2Tx-HT Interfacial Nanohybrid for Electrochemical Overall Water Splitting.

This study highlights the facet structure control of regular NixCo3-xO4 nanoplates and interfacial modulation through elemental doping and morphologically fitted assembly of Ti3C2Tx nanosheets for high performances in OER/HER and overall water splitting. Over the resulting Ni0.09Co2.91O4/Ti3C2Tx-HT in a solution of 1 M KOH, the OER and HER overpotentials of 262 and 210 mV, respectively, are achievable at a current density of 10 mA cm-2. In the case of the overall water splitting by using Ni0.09Co2.91O4/Ti3C2Tx-HT as anode and cathode catalysts, only a potential of 1.66 V is needed to obtain a current density of 10 mA cm-2, and the catalysts can stand for a period of 70 h, remarkably outperforming the RuO2-Pt/C-based catalyst and benefiting from the intensive association and interfacial function between the Ti3C2Tx and NixCo3-xO4 nanosheets. Interestingly, a surface reconstruction from the (112) to (111) facet structure occurred upon the fine-tuned Ni doping of regular NixCo3-xO4 hexagonal nanoplates and led to a highly active catalyst surface. At x = 0.09, the amount of Ni3+ becomes the highest, which is favorable for the generation of the critical OH intermediates on NixCo3-xO4/Ti3C2Tx-HT. The current study documented the significance of the well-controlled interfacial assembly of transition-metal oxide/MXenes as an effective electrocatalyst in the OER/HER and overall water splitting processes and provided the insights into the structure-performance correlation over such kinds of precious metal-free catalysts.

Achieving a Stable Solid Electrolyte Interphase and Enhanced Thermal Stability by a Dual-Functional Electrolyte Additive toward a High-Loading LiNi0.8Mn0.1Co0.1O2 /Lithium Pouch Battery.

Li metal batteries with high-capacity cathodes emerge as promising candidates for next-generation battery technologies. However, the poor reversibility of the Li deposition/stripping process severely reduces its lifespan, and safety also remains a major issue for the Li metal anodes. Herein, we propose (ethoxy)-penta-fluoro-cyclo-triphosphazene (DFA) as a dual-functional electrolyte additive to solve the engineering problem of balancing the cycle life and thermal stability of Li metal batteries. The NCM811/lithium metal pouch batteries (2900 mA h) are assembled using the commercial high areal capacity cathode (3.5 mA h cm-2). Compared with the NCM811/Li batteries without DFA, the heat generation and heat generation power of lithium metal batteries with DFA are significantly reduced by half during charging. Moreover, the NCM811/Li pouch batteries with DFA show excellent stability in both hot-oven and adiabatic rate calorimeter experiments. Furthermore, a nonlinear phase field simulation is carried out for mechanism investigation, which confirms that the stable solid electrolyte interphase formed by DFA will improve the cycle life of the NCM811/Li pouch. The DFA is verified to be an effective additive to improve the cycle stability and safety simultaneously, providing new opportunities for developing high energy density Li metal batteries.

Novel hierarchical urchin-like hollow SnO2 nanostructures with enhanced gas sensing performance.

Novel hierarchical urchin-like hollow SnO2 nanostructures have been synthesized via a facile one-pot template-free hydrothermal approach. The size and density of the SnO2 prickles as well as the morphology of the SnO2 spheres can be modified by tuning the synthetic parameters such as temperature, time, concentration, as well as pH value. The novel hierarchical nano-sized SnO2 hollow urchins possess enriched prickles with diameters of 5-20 nm and lengths of < 70 nm and high surface area up to 116 m2 g(-1), exhibiting advanced sensing performance to the ethanol vapor due to the special hierarchical nanostructures and being promising for the potential gas sensor material.

How to achieve a highly selective yet simply available vanadium phosphorus oxide-based catalyst for sustainable acrylic acid production via acetic acid-formaldehyde condensation.

A series of unsupported and supported vanadium phosphorus oxide catalysts were prepared by employing a new strategy, which significantly reduced the complexity of catalyst preparation. The greatly simplified catalyst fabrication benefits a greener and lower-cost process for practical applications. The currently fabricated systems showed ca. 90% target product(s) selectivity with a promising yield as well as catalyst durability.

Vanadium Phosphorus Oxide/Siliceous Mesostructured Cellular Foams: efficient and selective for sustainable acrylic acid production via condensation route.

A new type of supported vanadium phosphorus oxide (VPO) with self-phase regulation was simply fabricated (organic solvent free) for the first time by depositing the specific VPO precursor NH4(VO2)HPO4 onto the Siliceous Mesostructured Cellular Foams (MCF) with controlled activation. The resulting materials were found to be highly efficient and selective for sustainable acrylic acid (AA) plus methyl acrylate (MA) production via a condensation route between acetic acid (HAc) and formaldehyde (HCHO). A (AA + MA) yield of 83.7% (HCHO input-based) or a (AA + MA) selectivity of 81.7% (converted HAc-based) are achievable at 360 °C. The systematic characterizations and evaluations demonstrate a unique surface regulation occurring between the MCF and the NH4(VO2)HPO4 precursor. NH3 release upon activation of NH4(VO2)HPO4 precursor together with adsorption of NH3 by MCF automatically induces partial reduction of V5+ whose content is fine-tunable by the VPO loading. Such a functionalization simultaneously modifies phase constitution and surface acidity/basicity of catalyst, hence readily controls catalytic performance.

Strategy for nano-catalysis in a fixed-bed system.

For industry applications of nano-catalysts, the main bottlenecks are the low loading per unit support area and the slow flow rate through the support particles. By growing a dense Au nanowire forest on a loose network of glass fibers, continuous-flow catalysis can be achieved with a processing rate about 100 times that of the best literature rate.

Morphology-directed synthesis of Co3O4 nanotubes based on modified Kirkendall effect and its application in CH4 combustion.

We reported the morphology-directed synthesis of Co(3)O(4) nanotubes via interfacial reaction of NaOH with pre-fabricated CoC(2)O(4)·2H(2)O nanorods based on modified Kirkendall effect. The as-obtained Co(3)O(4) nanotubes showed excellent activity and durability in catalytic combustion of CH(4).

Core-shell structured microcapsular-like Ru@SiO2 reactor for efficient generation of CO(x)-free hydrogen through ammonia decomposition.

The core-shell structured microcapsular-like Ru@SiO(2) reactor is proved to be the most efficient material known to date for CO(x)-free hydrogen production via ammonia decomposition for fuel cells application. The very active Ru core particles can retain good stability even at high temperatures (up to 650 degrees C) thanks to the protection of the inert SiO(2) nano-shell.

In situ TA-MS study of the six-membered-ring-based growth of carbon nanotubes with benzene precursor.

By using the in situ thermal analysis-mass spectroscopic technique, combined with transmission electron microscopic characterization of the carbon nanotube (CNT) product, we have studied the chemical vapor deposition (CVD) growth of CNTs with Fe-Co/gamma-Al2O3 catalyst and benzene precursor in the range of room temperature to 700 degrees C. The growth process has been clearly illuminated, which starts from the reduction of catalyst around 645 degrees C followed by the dissociation of carbon-hydrogen bonds of benzene and the sequential growth of CNTs. A surprising fact is that no possible hydrocarbon species derived from benzene was detected, indicating that the carbon-carbon bond was not broken under our experimental conditions. All of the experimental results strongly reinforce the six-membered-ring-based growth model, and a schematic elucidation is presented accordingly. This in situ study not only reveals the unique and convincing information directly related to the growth mechanism from the involved chemistry, but also provides a powerful way to clarify the mechanism of CVD synthesis of CNTs with other precursors.