基于“认识规律”的电化学原理课程教学设计——电子转移步骤动力学

电化学原理课程是化学、化工、材料、环境工程和新能源等专业常开的一门课程,普遍使用的教材常以“学科思维”进行编写,不符合学生的认知规律。笔者基于“认知规律”对电化学原理课程中电子转移步骤动力学章节进行了重构,将有助于学生学习目标的达成,体现了新工科建设的思维和内涵。

Atomic Dispersed Hetero‑Pairs for Enhanced Electrocatalytic CO_(2)Reduction

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)involves a variety of intermediates with highly correlated reaction and ad-desorption energies,hindering optimization of the catalytic activity.For example,increasing the binding of the*COOH to the active site will generally increase the*CO desorption energy.Breaking this relationship may be expected to dramatically improve the intrinsic activity of CO_(2)RR,but remains an unsolved challenge.Herein,we addressed this conundrum by constructing a unique atomic dispersed hetero-pair consisting of Mo-Fe di-atoms anchored on N-doped carbon carrier.This system shows an unprecedented CO_(2)RR intrinsic activity with TOF of 3336 h−1,high selectivity toward CO production,Faradaic efficiency of 95.96%at−0.60 V and excellent stability.Theoretical calculations show that the Mo-Fe diatomic sites increased the*COOH intermediate adsorption energy by bridging adsorption of*COOH intermediates.At the same time,d-d orbital coupling in the Mo-Fe di-atom results in electron delocalization and facilitates desorption of*CO intermediates.Thus,the undesirable correlation between these steps is broken.This work provides a promising approach,specifically the use of di-atoms,for breaking unfavorable relationships based on understanding of the catalytic mechanisms at the atomic scale.

新兴的二维金属烯:结构调控和电催化应用进展

得益于超高的比表面积、高密度的表面活性原子和高度可调的微观结构,二维材料受到研究者的广泛关注.金属烯作为一种简化的、定义明确的模型体系,可以作为良好的载体固定单原子或金属纳米颗粒以获得高效的催化剂.其中,二维金属烯具有类石墨烯结构,是厚度小于5 nm的二维金属基纳米材料,已经在多种电化学反应中表现出较好的电催化性能.本文综述了金属烯在结构调控方面的最新进展,包括缺缺陷工程、相工程、应变工程、界面工程、掺杂和合金工程策略.(1)缺陷工程:缺陷的存在往往能调控材料的电子结构和配位状态,进而改善其催化活性,甚至缺陷位可以直接作为活性位来调控反应进程;(2)相工程:相工程策略包括晶相工程、无定型相工程和异质相工程,区别于热力学稳定的常规相,独特的原子排布方式赋予了非常规相较好的催化活性;(3)应变工程:应变工程不同于配位效应,它是一种长程作用,可大幅度提升材料的性能;(4)界面工程:界面是两种或多种物相的交界,通过各物种强有力的协同效应实现超高的活性;(5)掺杂与合金化:作为一种常规的调控策略,掺杂与合金化在提升材料性能上仍然发挥着巨大的作用.各类调控策略的发展,使得二维金属烯在能源电催化反应中展现出极具前景的应用,包括氧还原反应、二氧化碳还原反应、氢析出反应和小分子氧化反应.最后,本文提出了这一新兴领域的未来挑战和发展方向.

Cell Segmentation and Tracking in Microfluidic Platform

In this research, we have concentrated on trajectory extraction based on image segmentation and data association in order to provide an economic and complete solution for rapid microfluidic cell migration experiments. We applied region scalable active contour model to segment the individual cells and then employed the ellipse fitting technique to process touching cells. Subsequently, we have also introduced a topology based technique to associate the cells between consecutive frames. This scheme achieves satisfactory segmentation and tracking results on the datasets acquired by our microfluidic platform.

3D free-assembly modular microfluidics inspired by movable type printing

Reconfigurable modular microfluidics presents an opportunity for flexibly constructing prototypes of advanced microfluidic systems.Nevertheless,the strategy of directly integrating modules cannot easily fulfill the requirements of common applications,e.g.,the incorporation of materials with biochemical compatibility and optical transparency and the execution of small batch production of disposable chips for laboratory trials and initial tests.Here,we propose a manufacturing scheme inspired by the movable type printing technique to realize 3D free-assembly modular microfluidics.Double-layer 3D microfluidic structures can be produced by replicating the assembled molds.A library of modularized molds is presented for flow control,droplet generation and manipulation and cell trapping and coculture.In addition,a variety of modularized attachments,including valves,light sources and microscopic cameras,have been developed with the capability to be mounted onto chips on demand.Microfluidic systems,including those for concentration gradient generation,droplet-based microfluidics,cell trapping and drug screening,are demonstrated.This scheme enables rapid prototyping of microfluidic systems and construction of on-chip research platforms,with the intent of achieving high efficiency of proof-of-concept tests and small batch manufacturing.

Highly conductive polymer nanocomposites for emerging high voltage power cable shields:experiment,simulation and applications

High voltage power cables play a critical role in global electricity transmission and distribution.The currently used power cables cannot fulfil the green and sustainable requirement of modern society because of the thermoset nature of cable insulation and shields.This study is aimed at developing thermoplastic shields for high voltage power cable,which is one bottleneck restricting the development of environmental-friendly cables.Using carbon black(CB)as the main conductive component and a small amount of carbon nanotubes(CNTs)or graphene as the second filler,highly conductive polypropylene based composite materials were prepared for potential shield applications.It was found that,at a fixed conductive filler loading,the replacement of a small amount CB by CNTs can significantly enhance the electrical conductivity and suppress its temperature dependence.However,when CB was replaced by graphene,only limited enhancement of electrical conductivity could be achieved and the electrical conductivity is still highly dependent on temperature.Dissipative particle dynamics simulations demonstrated that the enhanced conduction property in the CNTs-containing composites could be understood by the shorter average distance between CB and CNTs.Finally,the coordination between the newly developed conductive composites and the environmental-friendly thermoplastic polypropylene insulation was evaluated via high voltage direct current measurements,and the results revealed that the CNTs-containing composites showed excellent suppression effect on the space charge injection and accumulation in the insulation.This research paved a new way for developing environmental-friendly high voltage power cable shields.

Recent advances in acoustofluidic separation technology in biology

Acoustofluidic separation of cells and particles is an emerging technology that integrates acoustics and microfluidics.In the last decade,this technology has attracted significant attention due to its biocompatible,contactless,and labelfree nature.It has been widely validated in the separation of cells and submicron bioparticles and shows great potential in different biological and biomedical applications.This review first introduces the theories and mechanisms of acoustofluidic separation.Then,various applications of this technology in the separation of biological particles such as cells,viruses,biomolecules,and exosomes are summarized.Finally,we discuss the challenges and future prospects of this field.

Mobility-limited charge injection in cross-linked polyethylene under extra high electric field

In this study,characteristics of charge injection under extra high electric field(above 100 kV/mm)in cross‐linked polyethylene(XLPE)were investigated by experiments of conduction current and space charge.The results show that current density from low electric field to sample breakdown corresponds to space charge limited current(SCLC)theory.More specifically,Schottky current is similar to experiment current before 100 kV/mm,while the J–E curve conforms to a modified SCLC theory after 100 kV/mm.Besides,the non‐linear coefficient of J–E curve from 100 kV/mm to extra high electric field is smaller than theoretical value,and the injection depth of space charge is restricted as the field becomes higher than 100 kV/mm,which may be caused by the negative differential mobility of charge.Driven by extra high electric field,charge collides with lattice of dielectric and scatters.As a result,mean free time of charge decreases and charge mobility is reduced with the increased field.Conse-quently,considering the decrease in charge mobility,a mobility‐limited charge injec-tion equation is proposed,and the validity of the proposed equation under extra high electric field is demonstrated by space charge simulation.

Insulation condition forewarning of form-wound winding for electric aircraft propulsion based on partial discharge and deep learning neural network

Form-wound windings in electric machines designed for electric aircraft propulsion face reliability challenges due to the severe operating environment,such as high temperature and low pressure.This study proposes a forewarning method for insulation condition monitoring of form-wound windings based on partial discharge(PD)and deep learning neural network.Three PD features are extracted from the PD profile,which provides information about physics-of-failure and reflects the degree of insulation degradation.An algorithm fusion extracted from auto-encoder and long short-term recurrent neural network is proposed to synthesize one failure precursor from these three features and make multi-time-step prediction through historical data to provide forewarning.An electrical and thermal accelerated ageing test is performed on the form-wound windings at 0.2 atm to simulate working environment of electric aircraft.The proposed method is validated on the accelerated ageing dataset and shows better prediction accuracy than some existing time-series prediction methods,indicating the advantages of the proposed method.Moreover,an on-line hardware setup using a deep learning processor is rec-ommended to implement the forewarning method.The proposed approach has the potential to be widely applied to other insulation systems and contribute to work on condition monitoring.