碱性阴离子膜燃料电池和电解水制氢技术对氢能的高效循环利用非常关键.然而,碱性条件下析氢反应（HER）和氢氧化反应（HOR）动力学缓慢,大大降低了燃料电池和电解池的能量转换效率.因此,开发综合性能优异的电催化剂以提高碱性环境下HER和HOR动力学至关重要.传统电催化剂的一个典型设计思路是将活性材料负载于具有高导电性和大比表面积的碳载体上.一般来说,碳载体能够促进活性材料的均匀分散并显著增加其催化活性位点的暴露,但是碳载体本身往往很难参与电催化反应,导致复合催化剂活性位点单一,不利于高效催化涉及较多中间体的复杂反应（碱性条件下的HOR和HER）.另一方面,当前电催化剂研究通常局限于调控活性材料和载体的界面结构或者专注于调控活性材料本征结构,对催化剂载体进行调控并作为助催化剂的研究尚不多见.本文采用过渡金属单原子对碳载体进行功能化及电子结构调控,并研究此类碳载体在碱性HER和HOR反应中的助催化作用,合成了一系列金属单原子修饰的碳载体M-N-C （过渡金属包括Mn,Fe,Co,Ni,Cu,Mo,Ag）,并系统研究了M-N-C在Pt电催化HOR和HER中的作用.结果表明,过渡金属单原子修饰的碳载体的催化促进作用与过渡金属的电负性以及3d轨道电子填充度密切相关.一方面,不同过渡金属M与氧的亲和力不同,并可以通过界面M-O-Pt键调节Pt的电子结构.过渡金属电负性越小,Pt表面的电子密度则越大,有助于加速Had在Pt表面的结合/解离步骤,因此提升了HOR和HER反应速率.另一方面,过渡金属的3d轨道未填充程度越高,则越有利于增强其与氧2p轨道的耦合作用,所形成的M-N4结构对于水分子和OHad的吸附也大大增强,最终通过促进Volmer步骤加快氢的电催化反应速率.结果显示,除Cu和Ag单原子修饰的碳载体之外,其它几种过渡金属功能化的碳载体均能够通过促进Volmer反应步骤以加快碱性条件下Pt的HOR和HER电催化反应速率,其中效果最为显著的是锰单原子修饰的碳载体.Mn-N-C/Pt (1.48 mA cmPt-2)的质量比交换电流密度比商业化20%Pt/C (0.26 mA cmPt-2)提高了约4.7倍.综上所述,本工作证明了开发多功能碳载体用于异相催化反应的重要性,并且为未来开发高效电催化剂提供了新的思路.
Two-dimensional(2D)heterostructures based on layered transition metal dichalcogenides(TMDs)have attracted increasing attention for the applications of the nextgeneration high-performance integrated electronics and ***...
详细信息
Two-dimensional(2D)heterostructures based on layered transition metal dichalcogenides(TMDs)have attracted increasing attention for the applications of the nextgeneration high-performance integrated electronics and *** various TMD heterostructures have been successfully fabricated,epitaxial growth of such atomically thin metal-semiconductor heterostructures with a clean and sharp interface is still *** addition,photodetectors based on such heterostructures have seldom been ***,we report the synthesis of high-quality vertical NbS2/MoS2metallic-semiconductor *** using NbS2as the contact electrodes,the field-effect mobility and current on-off ratio of MoS2can be improved at least 6-fold and two orders of magnitude compared with the conventional Ti/Au contact,*** using NbS2as contact,the photodetector performance of MoS2is much improved with higher responsivity and less response *** facile synthesis of atomically thin metal-semiconductor heterostructures by a simple chemical vapor deposition strategy and its effectiveness as ultrathin 2D metal contact open the door for the future application of electronics and optoelectronics.
暂无评论