摘要
The quest for low‐cost yet efficient non‐Pt electrocatalysts for the oxygen reduction reaction(ORR)has become one of the main focuses of research in the field of catalysis,which has implications for the development of the next generation of greener fuel cells.Here,we comprehensively describe the'big picture'of recent advances made in the rational design of ORR electrocatalysts,including molecule‐based,metal‐oxide‐based,metal‐nanomaterial‐based and two‐dimensional electrocatalysts.Transition metals can fabricate molecular electrocatalysts with N4‐macrocycles such as porphyrin‐class compounds and the so‐formed M-N-C active centre plays a crucial role in determining the catalytic performances towards the ORR.Group‐IV and‐V Transition metal oxides represent another class of promising alternative of Pt‐based catalysts for the ORR which catalytic activity largely depends on the surface structure and the introduction of surface defects.Recent advances in synthesis of metallic nanoparticles(NPs)allow for precise control over particle sizes and shapes and the crystalline facets exposed to enhance the ORR performance of electrocatalysts.Two‐dimensional materials such as functionalized grapheme or MoS2are emerging as novel electrocatalysts for the ORR.This review covers various aspects towards the design of future ORR electrocatalysts,including the catalytic performance,stability,durability and cost.Some novel electrocatalysts even surpass commercial Pt/C systems,demonstrating their potential to be alternatives in industrial applications.Despite the encouraging progress,challenges,which are also described,remain to be overcome before the real‐world application of novel ORR electrocatalysts.
燃料电池可以在接近室温条件下将氢或烃类中蕴含的巨大化学能通过电化学途径直接转化为清洁、稳定、可持续的电能,因而被视为极有前景的、能够满足日益增长的世界能源需求的终极解决方案之一.在一个典型的氢燃料电池中,氢在正极氧化而氧在负极还原,从动力学角度说,氧还原反应(ORR)比氢氧化反应进行的慢得多.无论是在酸性还是碱性条件下,氧的还原都可以一个四电子过程或是两个双电子过程进行,当然在酸性和碱性环境中反应的机理不同.铂一直是最有效的ORR催化剂,但受到价格昂贵、稳定性差和易中毒等因素的制约,目前非铂催化剂成为越来越引人瞩目的发展方向.本综述试图从分子催化剂、金属纳米材料催化剂、金属氧化物催化剂和新兴的二维材料催化剂等方面,选取近十年来最能代表ORR电化学催化剂方面成就的例子分析其优缺点,并为今后该领域的研究提供一些有益的思路.典型的分子催化剂是卟啉类化合物,当这种四齿的N4配体与过渡金属特别是铁、钴络合时,往往显示出良好的ORR催化性能,多数情况下其中的过渡金属中心、配体和碳支撑体系共同组成催化剂的活性中心.在另一些报道中,邻菲罗啉或是连吡啶型N_2化合物也可以作为配体使用.第四和第五副族的很多金属形成的不同价态的氧化物都具有氧还原活性,比如MnO_x,CoO_x,TiO_x,ZrO_x,IrO_x等.金属氧化物表现出易于修饰,不容易团聚和抗腐蚀等诸多优点,而其良好的ORR性能与表面的缺陷密切相关,因此钙钛矿型氧化物ABO_x也引起人们的广泛关注,人们可以通过调节氧化物的晶型、尺寸和组成来获得更好的催化性能.近年来随着液相合成技术的发展,人们可以制备出理想形状和尺寸的单分散纳米粒子,然后通过旋涂、自组装等手段将其修饰到合适的电极上以获得增强性能的ORR催化剂.通过形状�
基金
supported by the Australian Research Councile Discovery Projects(DP140100052,DP150103750)
Advanced Study and Training Program of Jiangsu Vocational Education(2016TDFX013)
High Level Talent Fund of Yancheng Vocational Institute of Health Sciences and Scientific Innovation Team Project of Yancheng Vocational Institute of Health Sciences~~
