大电流密度过渡金属硫族化合物析氢催化剂界面工程展望

氢能是未来可持续社会中理想的能量载体,利用可再生能源电解水制取绿氢的技术受到研究人员的广泛关注.电解水制绿氢技术由实验室向工业应用跨越的前提是发展大电流密度下性能优异且稳定的电催化剂.析氢反应(HER)是一种非均相反应,涉及催化剂-基底、催化剂-电解液、催化剂-气体三个界面.界面性质会影响电化学传质行为、电荷传输行为和催化剂的力学性质,从而影响大电流密度下制氢性能.因此,优化界面结构和性质是提升大电流密度下电解水催化剂性能并解决电解水技术工业应用挑战的关键.二维过渡金属硫族化合物(TMDCs)具有电子结构可调、活性位点丰富、合成方法多样等优势,自1976年首次应用于光电催化水分解反应、加氢脱硫反应以来,已有大量工作报道了TMDCs催化剂应用于HER.本文以TMDCs催化剂为例研究界面工程对大电流密度下HER的提升作用及机制.探讨了电化学反应中上述三个界面上发生的物理化学过程,系统分析了大电流密度下质量传输、电荷传输速率受限和力学强度不足三方面挑战,并总结了适用于大电流密度的催化剂性能描述符.分别归纳了针对以上三个界面的界面工程策略及相应作用,简要概括为:(1)催化剂-基底界面结合力增强、界面电阻降低、界面电子结构调控等策略;(2)催化剂-电解液界面形貌调控、表面化学、电解液环境调控等策略;(3)催化剂-气体界面疏气性调控、外场作用等策略.从反应机理研究、膜电极界面设计及电解槽界面性质调控三个角度对电解水反应界面工程未来的发展与应用提出了建议及展望.在反应机理方面,大电流条件下的界面性质如界面电阻、传质行为等仍需更深入的认识.在膜电极中,催化剂、离子交换膜、离子型聚合物、气体扩散层所形成的多元界面,尤其是催化剂-膜界面、催化剂-气体扩散层界面的结构仍需进一步优化以提升膜电极的活性及稳定性.在电解槽界面性质调控方面,催化剂-基底界面结合力等参数与催化剂寿命间的关系,电解过程中界面处的温度场及流场分布,适配于实际生产系统的电流密度等仍需深入研究.综上,本文从基本物理化学过程、策略及作用、挑战与展望等多个方面介绍了界面工程.本文有助于研究人员理解非均相电化学反应过程中界面的重要作用,提出催化剂、膜电极、电解槽界面设计新策略,并开发新型表征方法以深入对界面性质的认识,推动高效电解水技术的开发及应用.

摩擦力显微镜表征二维材料晶格结构研究

摩擦力显微镜(friction force microscopy,FFM)是一种基于摩擦力信号的原子力显微镜,能够对二维材料晶格进行快速、无损的高分辨成像.然而,由于热漂移、黏附力、表面静电等因素的影响,环境条件下二维材料的高分辨FFM成像仍面临着巨大挑战.基于以上问题,本文以高定向热解石墨为标准样品,通过对探针在样品表面黏滑行为的分析,系统研究了探针弹性常数、正应力和扫描速度对高分辨FFM成像的影响,并建立了一套可靠的二维材料晶格结构表征方法.该方法能够获得精确的结构信息,所测得的二维材料晶格常数平均误差小于2.3%.此外,该方法还适用于化学气相沉积法和剥离法制备的多种二维材料,展现出较高的普适性.本文的研究结果为环境条件下二维材料晶格结构的精确表征提供了新思路.

Homologous gradient heterostructure-based artificial synapses for neuromorphic computation

Gradient heterostructure is one of fundamental interfaces and provides an effective platform to achieve gradually changed properties in mechanics,optics,and electronics.Among different types of heterostructures,the gradient one may provide multiple resistive states and immobilized conductive fila-ments,offering great prospect for fabricating memristors with both high neuromorphic computation capability and repeatability.Here,we invent a memristor based on a homologous gradient heterostructure(HGHS),compris-ing a conductive transition metal dichalcogenide and an insulating homolo-gous metal oxide.Memristor made of Ta–TaS_(x)O_(y)–TaS 2 HGHS exhibits continuous potentiation/depression behavior and repeatable forward/backward scanning in the read-voltage range,which are dominated by multi-ple resistive states and immobilized conductive filaments in HGHS,respec-tively.Moreover,the continuous potentiation/depression behavior makes the memristor serve as a synapse,featuring broad-frequency response(10^(-1)–10^(5) Hz,covering 106 frequency range)and multiple-mode learning(enhanced,depressed,and random-level modes)based on its natural and moti-vated forgetting behaviors.Such HGHS-based memristor also shows good unifor-mity for 5?7 device arrays.Our work paves a way to achieve high-performance integrated memristors for future artificial neuromorphic computation.

Why do platinum catalysts show diverse electrocatalytic performance?

As one of the best electrocatalysts for the hydrogen evolution reaction,platinum catalysts are a benchmark for the performance evaluation of new catalysts.However,platinum catalysts reported in the literature show diverse electrocatalytic performances,resulting in the lack of a common reference standard.In this study,we investigated several factors that affect the performance of platinum catalysts by performing experimental measurements and data processing.These factors included the solution resistance,electrolyte temperature,loading quantity,catalyst microstructure,and normalization method of the current density.Finally,we recommended criteria for the performance evaluation of electrocatalysts.

Iodine-assisted ultrafast growth of high-quality monolayer MoS_(2) with sulfur-terminated edges

Two-dimensional(2D)semiconductors have attracted great attention to extend Moore’s law,which motivates the quest for fast growth of high-quality materials.However,taking MoS_(2) as an example,current methods yield 2D MoS_(2) with a low growth rate and poor quality with vacancy concentrations three to five orders of magnitude higher than silicon and other commercial semiconductors.Here,we develop a strategy of using an intermediate product of iodine as a transport agent to carry metal precursors efficiently for ultrafast growth of high-quality MoS_(2).The grown MoS_(2) has the lowest density of sulfur vacancies(~1.41×10^(12) cm^(−2))reported so far and excellent electrical properties with high on/off current ratios of 108 and carrier mobility of 175 cm^(2) V^(−1) s^(−1).Theoretical calculations show that by incorporating iodine,the nucleation barrier of MoS_(2) growth with sulfur-terminated edges reduces dramatically.The sufficient supply of precursor and low nucleation energy together boost the ultrafast growth of sub-millimeter MoS_(2) domains within seconds.This work provides an effective method for the ultrafast growth of 2D semiconductors with high quality,which will promote their applications.

Biomolecule capturing and sensing on 2D transition metal dichalcogenide canvas

Since the isolation of graphene in 2004,two-dimensional(2D)materials such as transition metal dichalcogenide(TMD)have attracted numerous interests due to their unique van der Waals structure,atomically thin body,and thickness-dependent properties.In recent years,the applications of TMD in public health have emerged due to their large surface area and high surface sensitivities,as well as their unique electrical,optical,and electrochemical properties.In this review,we focus on state-of-the-art methods to modulate the properties of 2D TMD and their applications in biosensing.Particularly,this review provides methods for designing and modulating 2D TMD via defect engineering and morphology control to achieve multi-functional surfaces for molecule capturing and sensing.Furthermore,we compare the 2D TMD-based biosensors with the traditional sensing systems,deepening our understanding of their action mechanism.Finally,we point out the challenges and opportunities of 2D TMD in this emerging area.

Mass production of two-dimensional materials beyond graphene and their applications

Two-dimensional(2D)materials are promising candidates in wide applications including energy storage and conversion,sensors,flexible devices,etc.The low-cost production of 2D materials with large quantities and demanded quality is the precondition for their commercial uses.For graphene and its derivatives,relatively mature techniques have been established for their scalable preparation and industrial applications.Whereas the mass production of 2D materials beyond graphene is still in its early age and it lacks a summary on this topic.This review systematically describes the state-of-the-art approaches for high-yield preparation of 2D materials beyond graphene,including“top-down”exfoliation and“bottom-up”synthetic approaches.In particular,each method is discussed from the perspectives of its principle,optimization attempts,characteristics of the obtained 2D materials,and its scalability potential.The applications that require massively-produced 2D materials are highlighted,including electrocatalysis,batteries,supercapacitors,mechanical and chemical sensors,as well as electromagnetic interference shielding and microwave absorption devices.Finally,we propose the challenges and opportunities for scalable preparation and commercial applications of 2D materials.

用于先进聚合物电解质水电解槽的膜电极工程

作为碳中和的重要能源载体,利用可再生能源电解水制取的“绿色氢能”受到了全世界的关注.聚合物电解质水电解槽因其优越的性能,有望成为未来绿色制氢市场的主流.当前,聚合物电解质水电解槽的发展受到膜电极发展缓慢的制约.膜电极是聚合物电解质水电解槽的重要组成部分,在很大程度上决定了水电解槽系统的成本和性能.因此,必须从降低成本和提高性能方面对膜电极组件进行优化,以促进其发展.在这篇综述中,我们首先讨论了膜电极材料的最新进展及现有的设计策略,包括催化剂的成本、活性和稳定性、离聚物的分布和厚度以及离子交换膜的离子传输效率.然后分析了所有组分和层间界面对膜电极中离子、电子和物质传输的影响,以及对电解槽性能的影响.最后,本论文就催化剂活性、离子交换膜稳定性、相邻组分之间的界面以及性能评估方法等方面提出了相关建议和展望.