Near-infrared sensitive differential Helmholtz-based hydrogen sulfide photoacoustic sensors.

A near-infrared (NIR) sub-ppm level photoacoustic sensor for hydrogen sulfide (H2S) using a differential Helmholtz resonator (DHR) as the photoacoustic cell (PAC) was presented. The core detection system was composed of a NIR diode laser with a center wavelength of 1578.13 nm, an Erbium-doped optical fiber amplifier (EDFA) with an output power of ∼120 mW, and a DHR. Finite element simulation software was used to analyze the influence of the DHR parameters on the resonant frequency and acoustic pressure distribution of the system. Through simulation and comparison, the volume of the DHR was 1/16 that of the conventional H-type PAC for a similar resonant frequency. The performance of the photoacoustic sensor was evaluated after optimizing the DHR structure and modulation frequency. The experimental results showed that the sensor had an excellent linear response to the gas concentration and the minimum detection limit (MDL) for H2S detection in differential mode can reach 460.8 ppb.

Amorphous Ge/C Composite Sponges: Synthesis and Application in a High-Rate Anode for Lithium Ion Batteries.

A Ge/C spongelike composite is prepared by the facile and scalable single-step pyrolysis of the GeOx/ethylenediamine gel process, which has a feature with three-dimensional interconnected pore structures and is hybridized with nitrogen-doped carbon. A detailed investigation shows that the pore in the sponge is formed for the departure of the gaseous products at the evaluated temperature. As an anode for lithium ion batteries, the obtained composite exhibits superior specific capacity in excess of 1016 mA h g-1 at 100 mA g-1 after 100 cycles. Moreover, the amorphous Ge/C sponge electrode also has a good rate capacity and stable cycling performance. The obtained amorphous Ge/C sponges are a good candidate anode for next-generation lithium ion batteries.

Oxygen vacancy-mediated amorphous GeOx assisted polysulfide redox kinetics for room-temperature sodium-sulfur batteries.

The practical applications of room-temperature sodium-sulfur (RT Na-S) batteries have been greatly hindered by the natural sluggish reaction kinetics of sulfur and the shuttle effect of sodium polysulfide (NaPSs). Herein, oxygen vacancy (OV)-mediated amorphous GeOx/nitrogen doped carbon (donated as GeOx/NC) composites were well designed as sulfur hosts for RT Na-S batteries. Experimental and density functional theory studies show that the introduction of oxygen vacancies on GeOx/NC can effectively immobilize polysulfides and accelerate the redox kinetics of polysulfides. Meanwhile, the micro-and mesoporous framework, acting as a reactor for storing active S, is conducive to alleviating the expansion of S during the charging/discharging process. Consequently, the S@GeOx/NC cathode affords a reversible capacity of 1017 mA h g-1 at 0.1 A g-1 after 100 cycles, outstanding rate capability of 333 mA h g-1 at 10.0 A g-1 and long lifespan cyclability of 385 mAh g-1 at 1 A g-1 after 1200 cycles. This work furnishes a new way for the rational design of metal oxides with oxygen vacancies and boosts the application for RT Na-S batteries.

Gallate-MOF derived CoS2/C composites as an accelerated catalyst for room-temperature sodium-sulfur batteries.

CoS2/C microprisms with adsorption-catalysis synergistic effects were designed to be sulfur hosts in room-temperature sodium-sulfur batteries. CoS2/C can act as a polysulfide mediator to inhibit the shuttle effect and as a catalyst to accelerate polysulfide redox kinetics, achieving enhanced capabilities of 623 mA h g-1 after 870 cycles at 1 A g-1.

Rational nanostructured FeSe2 wrapped in nitrogen-doped carbon shell for high-rate capability and long cycling sodium-ion storage.

Transition metal selenides (TMSs) have drawn substantial attention as promising anode materials for sodium-ion batteries (SIBs) on account oftheir rapid reaction kinetics and high reversible capacity. However, the undesirable capacity decay and inferior rate performance still hamper their large-scale application. Herein, an anode material comprising combination of olivary nanostructure FeSe2 core and nitrogen-doped carbon shell (designated as FeSe2@NC) is well designed by in-situ polymerization and selenization method. The well-designed nitrogen-doped carbon shell can not only alleviate the volume variation during the electrode cycling but also provide an optimized ion/electron transport pathway. The resulting FeSe2@NC electrodes exhibit a superior rate capability of 228.4 mA h g-1 at 10 A g-1 and a long cycling performance of 246.5 mA h g-1 at 5 A g-1 after 1000 cycles, which can be assigned to the enhanced structural integrity and improved electrical conductivity. The strategy would present a promising thought for structure design of TMSs as anode materials, which could enhance high-rate and long-lasting cycle performances for SIBs.