Xuemei Mu

Molybdenum Dioxide-Anchored Graphene Foam as a Negative Electrode Material for Supercapacitors

Molybdenum dioxide nanoparticles of diameter 100 nm were anchored uniformly to a three-dimensional (3D) graphene foam using an ultrasonication-assisted deposition method. X-ray diffraction and Raman spectroscopy indicated that the molybdenum dioxide nanoparticles had a monoclinic crystal structure. The 3D graphene/MoO2 nanoparticle composite showed excellent pseudocapacitive ability as its specific capacitance reached 404 F g−1 at a scan rate of 2 mV s−1 in the negative potential range, −1.0 to −0.2 V, in a neutral solution. Overall, the 3D graphene/MoO2 nanoparticle composite has great potential as an anode material for the next generation of high-performance supercapacitors.

Construction of Hierarchical CNT/rGO-Supported MnMoO4 Nanosheets on Ni Foam for High-Performance Aqueous Hybrid Supercapacitors

Rationally designed conductive hierarchical nanostructures are highly desirable for supporting pseudocapacitive materials to achieve high-performance electrodes for supercapacitors. Herein, manganese molybdate nanosheets were hydrothermally grown with graphene oxide (GO) on three-dimensional nickel foam-supported carbon nanotube structures. Under the optimal graphene oxide concentration, the obtained carbon nanotubes/reduced graphene oxide/MnMoO4 composites (CNT/rGO/MnMoO4) as binder-free supercapacitor cathodes perform with a high specific capacitance of 2374.9 F g-1 at the scan rate of 2 mV s-1 and good long-term stability (97.1% of the initial specific capacitance can be maintained after 3000 charge/discharge cycles). The asymmetric device with CNT/rGO/MnMoO4 as the cathode electrode and the carbon nanotubes/activated carbon on nickel foam (CNT-AC) as the anode electrode can deliver an energy density of 59.4 Wh kg-1 at the power density of 1367.9 W kg-1. These superior performances can be attributed to the synergistic effects from each component of the composite electrodes: highly pseudocapacitive MnMoO4 nanosheets and three-dimensional conductive Ni foam/CNTs/rGO networks. These results suggest that the fabricated asymmetric supercapacitor can be a promising candidate for energy storage devices.

A low temperature and highly sensitive ethanol sensor based on Au modified In2O3 nanofibers by coaxial electrospinning

Gas sensing is a powerful tool for detecting the leakage of some hazardous gases and monitoring human health. However, most of the sensors based on metal oxide semiconductors can only function at elevated operating temperatures, which leads to high power consumption and poor durability. Here, Au nanoparticle decorated In2O3 nanofibers (IO-Au NFs) have been successfully synthesized by one-step coaxial electrospinning for efficient sensing of ethanol gas at low temperature. The temperature and gas concentration effects on the sensing properties of the IO-Au NFs confirm that the Au decoration can remarkably improve the response, reduce the detection limit down to 1 ppm, and lower the sensors’ optimal operating temperature down to 175 °C. The IO-Au-0.42 sensor with the optimized Au concentration presents a superior response of 116.13 to 100 ppm ethanol at 175 °C, which is six times larger than that of the pristine In2O3 sensor. Moreover, the IO-Au-0.42 sensor exhibits a much shorter response/recovery time of 2 s/152 s to 100 ppm ethanol gas at 175 °C than the pristine In2O3. Surprisingly, even at room temperature, the IO-Au-0.42 sensor still presents a high response of 11.12 to 100 ppm ethanol, which is 5.4 times larger than that of the pristine In2O3 sensor, and shows a short response/recovery time of 47 s/351 s. This enhanced sensing performance at low temperature can be mainly ascribed to the synergistic action of the catalytic effect, spillover effect, electronic sensitization effect, and deficient oxygen concentration.