Showing papers by "University of Science and Technology Beijing published in 2022"

High-temperature polyimide dielectric materials for energy storage: theory, design, preparation and properties

Abstract: Dielectric capacitors with a high operating temperature applied in electric vehicles, aerospace and underground exploration require dielectric materials with high temperature resistance and high energy density.

Lithiophilic N-doped carbon bowls induced Li deposition in layered graphene film for advanced lithium metal batteries

Abstract: Lithium (Li) metal with high theoretical capacity and low electrochemical potential is the most ideal anode for next-generation high-energy batteries. However, the practical implementation of Li anode has been hindered by dendritic growth and volume expansion during cycling, which results in low Coulombic efficiency (CE), short lifespan, and safety hazards. Here, we report a highly stable and dendrite-free Li metal anode by utilizing N-doped hollow porous bowl-like hard carbon/reduced graphene nanosheets (CB@rGO) hybrids as three-dimensional (3D) conductive and lithiophilic scaffold host. The lithiophilic carbon bowl (CB) mainly works as excellent guides during the Li plating process, whereas the rGO layer with high conductivity and mechanical stability maintains the integrity of the composite by confining the volume change in long-range order during cycling. Moreover, the local current density can be reduced due to the 3D conductive framework. Therefore, CB@rGO presents a low lithium metal nucleation overpotential of 18 mV, high CE of 98%, and stable cycling without obvious voltage fluctuation for over 600 cycles at a current density of 1 mA·cm−2. Our study not only provides a good CB@rGO host and pre-Lithiated CB@rGO composite anode electrode, but also brings a new strategy of designing 3D electrodes for those active materials suffering from severe volume expansion.

Emerging frontiers of Z-scheme photocatalytic systems

Abstract: Solar-driven fuel production is considered a promising strategy to solve the growing global energy demands and environmental problems. Z-scheme heterojunctions have been reported to exhibit considerably improved photocatalytic fuel production due to enhanced light harvesting, spatially separated reductive and oxidative active sites, and strong redox capability. Understanding the fundamental principles of Z-scheme photocatalytic systems and mastering their improvement strategies will help greatly with the further development of highly efficient Z-scheme photocatalysts for solar-driven fuel production and other photocatalytic applications. Z-scheme photocatalysts have recently received tremendous attention because of their strong light utilization and redox ability. This cutting-edge photocatalytic platform allows photocatalysts to convert light into chemical energy with high activity, selectivity, and stability. In this review, we highlight some of the recent key contributions in the field, including fundamental principles, advanced characterization methods, and a series of photocatalytic applications (e.g., water splitting, CO2 reduction, N2 fixation, H2O2 production). Significant improvement strategies for Z-scheme photocatalysts are also discussed and summarized. With increasing achievements, Z-scheme photocatalytic systems (PSs) will make a historic breakthrough in activity, solar utilization, selectivity, and fabrication cost and move toward practical production in the near future. Z-scheme photocatalysts have recently received tremendous attention because of their strong light utilization and redox ability. This cutting-edge photocatalytic platform allows photocatalysts to convert light into chemical energy with high activity, selectivity, and stability. In this review, we highlight some of the recent key contributions in the field, including fundamental principles, advanced characterization methods, and a series of photocatalytic applications (e.g., water splitting, CO2 reduction, N2 fixation, H2O2 production). Significant improvement strategies for Z-scheme photocatalysts are also discussed and summarized. With increasing achievements, Z-scheme photocatalytic systems (PSs) will make a historic breakthrough in activity, solar utilization, selectivity, and fabrication cost and move toward practical production in the near future. a typical layered 2D material with puckered layers of phosphorus stacked together via van der Waals forces. the energy band formed by free electrons. a unique class of materials that combine extended π-conjugation with a permanently microporous skeleton. one of the most widely used theoretical calculation technologies. a Z-scheme photocatalyst that shows photocatalytic activity under all wavelengths of light. an emerging 2D layered transition-metal carbide/carbonitride/nitride. metal–semiconductor contact that has a negligible contact resistance relative to the bulk or series resistance of the semiconductor. the charge-transfer route in S-scheme mode resembles a macroscopic ‘step’ (from low CB to high VB; Figure 1D). MoS2 with unsaturated S atoms on exposed edges as reactive sites forms three stacked atomic layers. the energy band formed by valence electrons. the minimum energy required to move an electron from the interior of a solid to its surface. the photogenerated carrier transfer route looks like the letter Z.

A new understanding of the effect of Cr on the corrosion resistance evolution of weathering steel based on big data technology

Abstract: In this work, we studied the effect of Cr element on the corrosion resistance evolution of weathering steel based on corrosion big data technology. It suggested that corrosion big data technology is suitable for evaluation of the effect of microalloying Cr element on the corrosion evolution behavior of weathering steel. New understandings prove that the effect of Cr on the corrosion process is dynamic rather than static, the processes is affected by both of the environmental factors and the electrochemical or chemical reactions in the rust layer. Besides, Cr element has both beneficial effect and detrimental effect on the corrosion resistance of weathering steel. The beneficial effect is that the general corrosion resistance of Cr-additional steel is better than that of Cr-free steel, while the detrimental effect is that localized corrosion is intensified as the increase of Cr content in the Cr-additional steel.

Boosting photocatalytic hydrogen evolution: Orbital redistribution of ultrathin ZnIn2S4 nanosheets via atomic defects

Abstract: Defect engineering, inducing photo-excited electrons and holes to different surfaces of semiconductor photocatalyst, is an efficient strategy to improve the photocatalytic activity. A rapid heating-up hydrothermal technique is developed to regulate ZnIn2S4 crystal growth, then, ultrathin ZnIn2S4 nanosheets with In defect-rich [InS]6 interlayer but perfect [InS]4 and [ZnS]4 surface layers are successfully prepared (ultra-ZIS-VIn). Interestingly, the In defect, inducing the redistribution of the orbitals near the valence band maximum, separates the oxidation and reduction sites on the opposite sides of the ultra-ZIS-VIn nanosheets. Simultaneously, In defects increase the density of states (near the valence band maximum and conduction band minimum) and delocalize the electron around In defects. Accordingly, the photocatalytic hydrogen evolution rate is optimized to 13.4 mmol h−1 g−1, which is 8.9 times higher than that of defect-free ZnIn2S4 (pristine-ZIS).

Waste cooking oil used as carbon source for microbial lipid production: Promoter or inhibitor

Abstract: In this study, waste cooking oil (WCO) co-fermentation with food waste by variable pH strategy was developed for microbial lipid production. Results showed that when WCO substitution rate within the range of 1.56-4.68% (corresponding to the WCO content in food waste), lipid production from Rhodosporidium toruloides 2.1389 could be increased by 7.2 g/kg food waste because of the better synergistic effect. Mechanism analysis revealed that the fatty acid salt produced from WCO under alkaline condition, as a surface active agent, could improve lipid production, but excessive WCO (29.2 g/L) would inhibit the lipid production due to its hindrance to the oxygen. The lipid composition analysis found that the produced lipid could be used as raw material for biodiesel production. It was estimated that 15.0 million tonnes of biodiesel could be produced from global food waste yearly by adopting the proposed WCO co-fermentation with variable pH strategy, together with reduction of about 0.31 million tonnes of CO2 equivalents and 1435 tonnes of SO2. It is expected that this study may lead to the paradigm shift in future biodiesel production from food waste.

Excellent heat transfer and phase transformation performance of erythritol/graphene composite phase change materials

Abstract: As a phase change material, erythritol has two main disadvantages: low thermal conductivity and high supercooling degree. In this study, we proposed a novel erythritol/graphene composite phase change material, and its thermal properties were predicted by molecular dynamics simulation. The effects of the graphene mass fraction, size and number of layers on the thermal conductivity and phase transition characteristics, including the melting point and supercooling degree, were analyzed. The mechanism behind the above phenomena was revealed from a micro perspective. The results show that graphene can not only improve the thermal conductivity of the composites but also reduce the supercooling degree, thus improving the thermal properties of erythritol. The thermal conductivity of the composites increases with increasing graphene amount, size and number of layers. When the mass fraction of graphene increased to 8 wt%, the thermal conductivity doubled. The melting point of erythritol can be effectively controlled by changing the amount, size and number of layers of graphene. This study can provide guidance for the design and application of erythritol-based composite phase change materials.

Enhanced oxygen reduction kinetics of IT-SOFC cathode with PrBaCo₂O_5+<i>δ</i>/Gd_0.1Ce_1.9O_{2−<i>δ</i>} coherent interface

Abstract: A PBC–GDC composite with coherent interface structure shows remarkable ORR activity and low polarization resistance under IT-SOFC service conditions.