In recent years, there has been increasing interest in synthesis of reduced graphene oxide (rGO)-metal oxide semiconductor (MOS) nanocomposites for room temperature gas sensing applications. Generally, the sensitivity of a MOS can be obviously enhanced by the incorporation of rGO. However, a lack of knowledge regarding how rGO can enhance gas-sensing performances of MOSs impedes its sensing applications. Herein, in order to get an insight into the sensing mechanism of rGO-MOS nanocomposites and further improve the sensing performances of NiO-based sensors at room temperature, an rGO-NiO nanocomposite was synthesized. Through a comparison study on room temperature NO2 sensing of rGO-NiO and pristine NiO, an inverse gas-sensing behavior in different NO2 concentration ranges was observed and the sensitivity of rGO-NiO was enhanced obviously in the high concentration range (7-60 ppm). Significantly, the stimulating effect of rGO on the recovery rate was confirmed by the sensing characteristics of rGO-NiO that was advantageous for the development of NO2 sensors at room temperature. By comprehending the electronic interactions between the rGO-MOS nanocomposite and the target gas, this work may open up new possibilities for further improvement of graphene-based hybrid materials with even higher sensing performances.

Rare-earth-based AB2-type compounds with Laves phase structure are readily subject to hydrogen-induced amorphization and disproportionation upon hydrogenation. In this work, we conducted the Sc alloying on Y0.95Ni2 to improve its hydrogen storage properties. The results show that the amorphization degree of Y0.95Ni2 deepens with the increasing hydrogenation time, pressure, and temperature. The Y(Sc)0.95Ni2 ternary compounds show a significant improvement in reversibility and dehydriding thermodynamics due to the reduced atomic radius ratio RA/RB and cell volume. Hydrogen-induced amorphization is fully eliminated in the Y0.25Sc0.7Ni2. The Y0.25Sc0.7Ni2 delivers a reversible hydrogen storage capacity of 0.94 wt.% and the dissociation pressure of 0.095 MPa at the minimum dehydrogenation temperature of 100 °C.

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