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3D nanoflower-like CuxO/multilayer graphene composites (CuMGCs) have been successfully synthesized as a new type of room temperature NOx gas sensor. Firstly, the expanded graphite (EG) was activated by KOH and many moderate functional groups were generated; secondly, Cu(CH3COO)2 and CTAB underwent full infusion into the interlayers of activated EG (aEG) by means of a vacuum-assisted technique and then reacted with the functional groups of aEG accompanied by the exfoliation of aEG via reflux. Eventually, the 3D nanoflower consisting of 5-9 nm CuxO nanoparticles homogeneously grow in situ on aEG. The KOH activation of EG plays a key role in the uniform formation of CuMGCs. When being used as gas sensors for detection of NOx, the CuMGCs achieved a higher response at room temperature than that of the corresponding CuxO. In detail, the CuMGCs show a higher NOx gas sensing performance with low detection limit of 97 ppb, high gas response of 95.1% and short response time of 9.6 s to 97.0 ppm NOx at room temperature. Meanwhile, the CuMGC sensor presents a favorable linearity, good selectivity and stability. The enhancement of the sensing response is mainly attributed to the improved conductivity of the CuMGCs. A series of Mott-Schottky and EIS measurements demonstrated that the CuMGCs have much higher donor densities than CuxO and can easily capture and migrate electrons from the conduction band, resulting in the enhancement of electrical conductivity.

In this paper, highly mesoporous hierarchical nickel and cobalt double hydroxide composites (NCDHs) have been synthesized via a simple reflux method. The synthesized NCDH composites with a mass ratio of 100 : 20 for Ni(NO 3 ) 2 $6H 2 O/Co(NO 3 ) 2 $6H 2 O (NCDH-20) contained a lot of oxygen defect sites, and chemisorbed water connects the adjacent Ni(OH) 2 layers. The porous hierarchical nanostructures provide natural channels for the effective and fast transportation of carriers. Furthermore, the NCDH-20 sensor exhibits excellent gas-sensing properties, such as a low detection limit of 0.97 ppm and short response time of 0.6 s to 97 ppm NO x , due to the layered single crystal structure and unique gallery pathway. The NCDH-20 sensor with ultrafast NO x sensing has significant applications for gas sensing.

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Biomass derivative carbonaceous materials are extremely fascinating for developing advanced energy storage devices according to unique architecture. Here, inspired by dandelion with consecutive hollow channel, nitrogen-doped hollow carbon framework (NHCF) as sulfur host was obtained via a simple thermal calcination in ammonia atmosphere for lithium–sulfur battery. The NHCF can effectively confine polysulfides and electrochemical reaction within the hollow channel and expedite lithium ion diffusion and electrode transport through porous nitrogen-doped carbon rampart. With this strategy, a high-level active sulfur loading of 80% and high sulfur utilization can be realized. As a result, the NHCF/S delivered an advanced initial capacity of 950 mAh g–1 at the rate of 0.5 C with small capacity fading rates of 0.049% per cycle after 500 cycles. Additionally, an average reversible areal capacity of nearly 5 mAh cm–2 was realized under raised sulfur mass loading of 5.5 mg cm–2. This superior electrochemical energy storage property endows renewable biomass derived carbon host with promising potential for low-cost rechargeable battery application.

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