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

Trace removal of benzene vapour using double-walled metal–dipyrazolate frameworks

Abstract: Abstract In principle, porous physisorbents are attractive candidates for the removal of volatile organic compounds such as benzene by virtue of their low energy for the capture and release of this pollutant. Unfortunately, many physisorbents exhibit weak sorbate–sorbent interactions, resulting in poor selectivity and low uptake when volatile organic compounds are present at trace concentrations. Herein, we report that a family of double-walled metal–dipyrazolate frameworks, BUT-53 to BUT-58, exhibit benzene uptakes at 298 K of 2.47–3.28 mmol g −1 at <10 Pa. Breakthrough experiments revealed that BUT-55, a supramolecular isomer of the metal–organic framework Co(BDP) (H 2 BDP = 1,4-di(1 H -pyrazol-4-yl)benzene), captures trace levels of benzene, producing an air stream with benzene content below acceptable limits. Furthermore, BUT-55 can be regenerated with mild heating. Insight into the performance of BUT-55 comes from the crystal structure of the benzene-loaded phase (C 6 H 6 @BUT-55) and density functional theory calculations, which reveal that C–H···X interactions drive the tight binding of benzene. Our results demonstrate that BUT-55 is a recyclable physisorbent that exhibits high affinity and adsorption capacity towards benzene, making it a candidate for environmental remediation of benzene-contaminated gas mixtures.

A review of flywheel energy storage systems: state of the art and opportunities

Abstract: Thanks to the unique advantages such as long life cycles, high power density, minimal environmental impact, and high power quality such as fast response and voltage stability, the flywheel/kinetic energy storage system (FESS) is gaining attention recently. There is noticeable progress in FESS, especially in utility, large-scale deployment for the electrical grid, and renewable energy applications. This paper gives a review of the recent developments in FESS technologies. Due to the highly interdisciplinary nature of FESSs, we survey different design approaches, choices of subsystems, and the effects on performance, cost, and applications. This review focuses on the state of the art of FESS technologies, especially those commissioned or prototyped. We also highlighted the opportunities and potential directions for the future development of FESS technologies.

Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution

Abstract: Polymeric carbon nitride (C3N4) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H2O2) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C3N4 nanosheets to form a homojunction structure (HJ-C3N4), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H2O2 yield of the HJ-C3N4 reached 115 μmol·L−1·h−1 in pure water by visible light, which has an 8.6x higher production than g-C3N4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment.

High-spin state Fe(III) doped TiO2 for electrocatalytic nitrogen fixation induced by surface F modification

Abstract: It is a challenging task to overcomes the bottleneck of N2 adsorption and activation in N2 reduction reaction (NRR). Regulating the catalyst surface electronic state is treated as a potential strategy to prevail over the barrier. Here, Incorporating Fe as a dopant in the TiO2 nanoparticles can generate oxygen vacancies and dopant energy levels, promoting the adsorption and activation of N2 molecules. F surface modification induces Fe (III) in the high spin state and upshifts the dopant energy level. That facilitates Fe 3d electrons backdonation to N 1πg* orbital promotes the activation of N2 molecule and reduces the limiting potential of NRR. Therefore, F-Fe: TiO2 electrocatalyst achieved the highest Faradaic efficiency and maximum NH3 production rate of 27.67% and 27.86 µg h 1 mgcat. 1 at −0.5 V v.s. reversible hydrogen electrode. This work provides deep insights into the design surface electronic state of catalyst toward efficient N2 to NH3 conversion.

High-spin state Fe(III) doped TiO2 for electrocatalytic nitrogen fixation induced by surface F modification

Abstract: It is a challenging task to overcomes the bottleneck of N2 adsorption and activation in N2 reduction reaction (NRR). Regulating the catalyst surface electronic state is treated as a potential strategy to prevail over the barrier. Here, Incorporating Fe as a dopant in the TiO2 nanoparticles can generate oxygen vacancies and dopant energy levels, promoting the adsorption and activation of N2 molecules. F surface modification induces Fe (III) in the high spin state and upshifts the dopant energy level. That facilitates Fe 3d electrons backdonation to N 1πg* orbital promotes the activation of N2 molecule and reduces the limiting potential of NRR. Therefore, F-Fe: TiO2 electrocatalyst achieved the highest Faradaic efficiency and maximum NH3 production rate of 27.67% and 27.86 µg h1 mgcat.1 at −0.5 V v.s. reversible hydrogen electrode. This work provides deep insights into the design surface electronic state of catalyst toward efficient N2 to NH3 conversion.

Adaptive Decentralized Asymptotic Tracking Control for Large-Scale Nonlinear Systems With Unknown Strong Interconnections

Abstract: An adaptive decentralized asymptotic tracking control scheme is developed in this paper for a class of large-scale nonlinear systems with unknown strong interconnections, unknown time-varying parameters, and disturbances. First, by employing the intrinsic properties of Gaussian functions for the interconnection terms for the first time, all extra signals in the framework of decentralized control are filtered out, thereby removing all additional assumptions imposed on the interconnections, such as upper bounding functions and matching conditions. Second, by introducing two integral bounded functions, asymptotic tracking control is realized. Moreover, the nonlinear filters with the compensation terms are introduced to circumvent the issue of “explosion of complexity”. It is shown that all the closed-loop signals are bounded and the tracking errors converge to zero asymptotically. In the end, a simulation example is carried out to demonstrate the effectiveness of the proposed approach.

The Impact of Green Technology Innovation on Carbon Emissions in the Context of Carbon Neutrality in China: Evidence from Spatial Spillover and Nonlinear Effect Analysis

Abstract: The Paris agreement is a unified arrangement for the global response to climate change and entered into force on 4 November 2016. Its long-term goal is to hold the global average temperature rise well below 2 °C. China is committed to achieving carbon neutrality by 2060 through various measures, one of which is green technology innovation (GTI). This paper aims to analyze the levels of GTI in 30 provinces in mainland China between 2001 and 2019. It uses the spatial econometric models and panel threshold models along with the slack based measure (SBM) and Global Malmquist-Luenberger (GML) index to analyze the spatial spillover and nonlinear effects of GTI on regional carbon emissions. The results show that GTI achieves growth every year, but the innovation efficiency was low. China's total carbon dioxide emissions were increasing at a marginal rate, but the carbon emission intensity was declining year by year. Carbon emissions were spatially correlated and show significant positive agglomeration characteristics. The spatial spillover of GTI plays an important role in reducing carbon dioxide emissions. In the underdeveloped regions in China, this emission reduction effect was even more significant.

Recovery of spent LiCoO2 lithium-ion battery via environmentally friendly pyrolysis and hydrometallurgical leaching

Abstract: LiCoO2 (LCO) lithium-ion battery (LIB) is rich in valuable metals (cobalt and lithium), which has high recycling value. The existing process has basically realized the extraction of cobalt, but there are still shortcomings in harmless disposal of fluorine-containing electrolyte, binder and other organic matters, selective extraction of lithium and low-cost extraction of cobalt. In this context, a novel process was developed to realize the full-component recovery of spent LiCoO2 battery via environmentally friendly pyrolysis and hydrometallurgical leaching. The organic matters were recovered in the form of pyrolytic oil and gas, in which the harmful fluorine element was absorbed by Ca(OH)2 solution. The current collectors (copper and aluminum) were recovered after the easy separation of electrode materials due to the degradation of binders. During pyrolysis the cathode material was deconstructed and reduced under the synergistic effect of pyrolytic gas and anode graphite. Selective recovery of lithium and cobalt was achieved through carbonated water leaching and reductant-free acid leaching. The leaching efficiencies of lithium and cobalt were respectively 87.9% and 99.1% under the optimal conditions. Lithium carbonate and cobalt sulfate were obtained by evaporative crystallization, respectively. The remaining residue was only graphite without impurity entrainment. The results in this research suggest that the process consisting of pyrolysis and hydrometallurgical leaching is inexpensive, efficient, and eco-friendly for full-component recycling of spent LiCoO2 battery.

Hierarchical mesoporous zinc oxide microspheres for ethanol gas sensor

Abstract: The increasing demand for hazardous gas detections has triggered the enormous efforts for the development of mesoporous materials for gas sensors. Especially, a universal method to synthesize such structure for semiconductor oxides is highly desirable. In this work, ZnO microspheres assembled by mesoporous nanosheets are prepared via a one-step hydrothermal method successfully. It is found that the morphology of ZnO and the thickness of ZnO mesoporous nanosheets, which affect the gas sensing response to ethanol, can be regulated by adjusting the amount of PVP. In addition, this method is also suitable for the synthesis of NiO, CuO and Co3O4 mesoporous nanosheets and the repeatability is excellent. Gas sensing investigation indicates that the gas sensors based on mesoporous ZnO nanospheres synthesized with 3.3 g PVP have the highest response (~58.4) to 100 ppm ethanol at 250°C, which is about 9.4 times higher than that of the ZnO nanosheets obtained without PVP under the same test conditions (~6.2). Furthermore, the detection limit could reach the ppb level with the response of 1.17–500 ppb ethanol. The possible mechanism of the formed structures and the enhanced ethanol sensing properties are discussed systematically.