Grain Boundary Control of Organic Semiconductors via Solvent Vapor Annealing for High-Sensitivity NO2 Detection

The microstructure of the organic semiconductor (OSC) active layer is one of the crucial topics to improve the sensing performance of gas sensors. Herein, we introduce a simple solvent vapor annealing (SVA) process to control 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) OSC films morphology and thus yields high-sensitivity nitrogen organic thin-film transistor (OTFT)-based nitrogen dioxide (NO2) sensors. Compared to pristine devices, the toluene SVA-treated devices exhibit an order of magnitude responsivity enhancement to 10 ppm NO2, further with a limit of detection of 148 ppb. Systematic studies on the microstructure of the TIPS-pentacene films reveal the large density grain boundaries formed by the SVA process, improving the capability for the adsorption of gas molecules, thus causing high-sensitivity to NO2. This simple SVA processing strategy provides an effective and reliable access for realizing high-sensitivity OTFT NO2 sensors

Effect of Vertical Annealing on the Nitrogen Dioxide Response of Organic Thin Film Transistors

Nitrogen dioxide (NO2) sensors based on organic thin-film transistors (OTFTs) were fabricated by conventional annealing (horizontal) and vertical annealing processes of organic semiconductor (OSC) films. The NO2 responsivity of OTFTs to 15 ppm of NO2 is 1408% under conditions of vertical annealing and only 72% when conventional annealing is applied. Moreover, gas sensors obtained by vertical annealing achieve a high sensing performance of 589% already at 1 ppm of NO2, while showing a preferential response to NO2 compared with SO2, NH3, CO, and H2S. To analyze the mechanism of performance improvement of OTFT gas sensors, the morphologies of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) films were characterized by atomic force microscopy (AFM) in tapping mode. The results show that, in well-aligned TIPS-pentacene films, a large number of effective grain boundaries inside the conducting channel contribute to the enhancement of NO2 gas sensing performance

Exploiting Na2MnPO4F as a high-capacity and well-reversible cathode material for Na-ion batteries

A Na2MnPO4F/C nanocomposite material is successfully synthesized via spray drying, followed by a high-temperature sintering method. It is shown that the highly phase-pure Na2MnPO4F with symmetry of the P21/n space group is uniformly embedded in the carbon networks, which play a key role in building up a highly efficient, electron-flow channel and elevating the electronic conductivity of the nanocomposites. The electrochemical measurements show that the initial discharge capacity of Na2MnPO4F reaches up to 140 and 178 mA h g-1at 30 °C and 55 °C, respectively. Furthermore, the capacity still maintains 135 mA h g-1after 20 cycles at 55 °C. The Na+diffusion coefficient in Na2MnPO4F is calculated at about 10-17cm2s-1by the GITT method. The impressive cycling performance of the material is ascribed to the good structural reversibility and stability of Na2MnPO4F, which are confirmed by the ex situ XRD measurements during the first cycle and after 30 cycles. This journal is ? the Partner Organisations 2014

A hierarchical porous Fe-N impregnated carbon-graphene hybrid for high-performance oxygen reduction reaction

A Fe-N impregnated carbon in a hybrid with in-situ grown graphene from hierarchical porous carbon has been obtained for high-performance oxygen reduction reaction (ORR) catalysis. This hybrid material combines the desirable characteristics for the ORR, including Fe-N active sites, high surface area, good electron conductivity, and hierarchical channels for mass diffusion. As a result, this catalyst exhibits a very positive reaction onset potential ( 0.05 V vs. Ag/AgCl), a high ORR current density, and a complete four-electron ORR pathway, which are even better than a commercial 20% Pt/C catalyst. We further reveal the synergistic ORR enhancement from the controlled Fe-N impregnation in the doped carbon-graphene hybri

A wheat flour derived hierarchical porous carbon/graphitic carbon nitride composite for high-performance lithium–sulfur batteries

© 2020 Elsevier Ltd To buffer the volume variation of sulfur and suppress the shuttle effect of long-chain lithium polysulfides during the cycling of Li-S batteries, it is essential to simultaneously design suitable pore structures and tune the surface chemistry of carbon-based sulfur hosts. However, the associated low yield and high cost of such delicately constructed carbon materials have been the major bottleneck for their practical utilization. Herein, we present a hundred-gram fabrication of a graphitic carbon nitride@hierarchical porous carbon (g-C3N4@HPC) composite, which is derived from low-cost biomass and used as the sulfur host for Li-S batteries. On this material, interconnected and hierarchical porosity of HPC physically traps the polysulfides and buffers the volume variation, and in the meantime, the uniformly dispersed g-C3N4 nanoparticles and N dopants on it provide strong chemical affinity to further immobilize the polysulfides. Therefore, the g-C3N4@HPC/S cathode delivers a high initial capacity of 1150.1 mAh g−1 and excellent cycling stability with a very small capacity decay of 0.024% cycle−1 for 250 cycles, at a high sulfur loading of 64.5 wt%. Importantly, this g-C3N4@HPC composite is derived from very cheap and eco-friendly precursors, enabling the hundred-gram production at bench-top scale, which shows significant viability for practical Li-S battery application

A wheat flour derived hierarchical porous carbon/graphitic carbon nitride composite for high-performance lithium–sulfur batteries

© 2020 Elsevier Ltd To buffer the volume variation of sulfur and suppress the shuttle effect of long-chain lithium polysulfides during the cycling of Li-S batteries, it is essential to simultaneously design suitable pore structures and tune the surface chemistry of carbon-based sulfur hosts. However, the associated low yield and high cost of such delicately constructed carbon materials have been the major bottleneck for their practical utilization. Herein, we present a hundred-gram fabrication of a graphitic carbon nitride@hierarchical porous carbon (g-C3N4@HPC) composite, which is derived from low-cost biomass and used as the sulfur host for Li-S batteries. On this material, interconnected and hierarchical porosity of HPC physically traps the polysulfides and buffers the volume variation, and in the meantime, the uniformly dispersed g-C3N4 nanoparticles and N dopants on it provide strong chemical affinity to further immobilize the polysulfides. Therefore, the g-C3N4@HPC/S cathode delivers a high initial capacity of 1150.1 mAh g−1 and excellent cycling stability with a very small capacity decay of 0.024% cycle−1 for 250 cycles, at a high sulfur loading of 64.5 wt%. Importantly, this g-C3N4@HPC composite is derived from very cheap and eco-friendly precursors, enabling the hundred-gram production at bench-top scale, which shows significant viability for practical Li-S battery application