长春应化所金属氮碳氧还原催化剂的研究进展

氧还原反应是燃料电池的核心,开发高性能催化剂一直是燃料电池技术面临的严峻挑战. 近年来,热解M-N-C催化剂的发展和以金属有机骨架材料为前驱体的运用让非贵金属氧还原催化剂的性能大幅度提升,但催化活性位点、反应机理等方面仍不甚清晰,需要分子水平上进一步的研究. 在这里,作者总结了本课题组近些年来在氧还原方向上的研究成果,首先是对催化剂活性位点进行的相关探索,提出了新的活性位点结构,为开发新型催化剂提供了帮助,并对金属氮碳催化剂进行了细致的微观调控,探讨了最佳的合成方法;其次开发了高效的双原子Co₂N₅催化剂,并在理论计算的指导下合成出了更为高效的FeCo双原子催化剂,具备了替代铂基催化剂的性能;最后针对芬顿反应引发的稳定性问题而开发的低芬顿反应活性的单原子Cr和单原子Ru催化剂,表现出了较高的活性和稳定性,为解决催化剂实际应用问题开辟了新的研究思路与方向. 作者相信,通过对催化剂活性位点的不断认知和对新型催化剂的不断开发,终会让非贵金属催化的商业化应用成为现实.     

Co，Cu共掺杂ZnO薄膜的结构及发光特性

采用电子束蒸发沉积成膜工艺在单晶Si(111)衬底上制备出Co,Cu共掺杂的Zn0.85-xCo0.15CuxO(x=0,0.04,0.06)多晶膜。采用X射线衍射(XRD)研究了Co、Cu掺杂对其微结构的影响;室温下测量了Zn0.85-xCo0.15CuxO薄膜的光致发光谱,发现随着Cu掺杂量的增加,样品发光增强,当Cu掺杂x=0.06时,Zn0.85-xCo0.15CuxO薄膜的PL谱中出现了较强的双峰蓝光发射;分析了掺杂含量对其发光性能的影响,并对样品的发光机制进行了探讨,并推断出蓝光峰来源于电子由导带底到锌空位(VZn)能级的跃迁及锌填隙(Zni)能级到价带顶的跃迁。     

Fe,Cu-codoped metal-nitrogen-carbon catalysts with high selectivity and stability for the oxygen reduction reaction

Metal-nitrogen-carbon materials(M-N-C) are non-noble-metal-based alternatives to platinum-based catalysts and have attracted tremendous attention due to their low-cost,high abundance,and efficient catalytic performance towards the oxygen reduction reaction(ORR).Among them,Fe-based materials show remarkable ORR activity,but they are limited by low selectivity and low stability.To address these issues,herein,we have synthesized FeCu-based M-N-C catalysts,inspired by the bimetal center of cytochrome c oxidase(CcO).In acidic media,the selectivity was notably improved compared with Febased materials,with peroxide yields less than 1.2%(<1/3 of the hydrogen peroxide yields of Fe-N-C catalysts).In addition to Cu-N-C catalysts which can catalytically reduce hydrogen peroxide,the reduction current of hydrogen peroxide using FeCu-N-C-20 exceeded that of Fe-N-C by about 6% when the potential was greater than 0.4 V.Furthermore,FeCu-based M-N-C catalysts suffered from only a15 mV attenuation in their half-wave potentials after 10,000 cycles of accelerated degradation tests(ADT),while there was a 30 mV negative shift for Fe-N-C.Therefore,we propose that the H₂O₂ released from Fe-Nx sites or N-doped carbon sites would be reduced by adjacent Cu-Nx sites,re sulting in low H₂O₂ yields and high stability.     

基于内嵌钴/氮掺杂多孔碳三维石墨烯笼的抗团聚高效氧还原电催化剂

氧还原反应是决定燃料电池、金属-空气电池等多种新型清洁能源存储与转化技术之性能与应用的关键反应. 铂及其合金是目前催化活性最好的氧还原反应催化剂,但其高昂的成本限制了规模化应用. 在小尺寸效应作用下,微纳米结构催化剂颗粒在电极制备与电化学反应过程中的团聚限制了催化剂本征催化活性的充分发挥. 本文基于喷雾热解技术,发展了一种基于内嵌钴/氮掺杂多孔碳三维石墨烯笼的高活性、抗团聚非贵金属氧还原反应催化剂. 此结构中,金属有机骨架化合物ZIF-67衍生的钴/氮掺杂多孔碳纳米结构是催化氧还原反应的活性中心,包覆其外的三维石墨烯笼不仅可在钴/氮掺杂碳纳米结构之间构建连续的三维载流子传导网络,且可高效抑制其在催化剂制备与电化学反应过程中的团聚与活性损失. 在碱性电解液中,此类非贵金属催化剂表现出可与铂基催化剂媲美的氧还原反应活性和优异的稳定性.     

Caging Porous Co-N-C Nanocomposites in 3D Graphene as Active and Aggregation-Resistant electrocatalyst for Oxygen Reduction Reaction北大核心CSCD

Oxygen reduction reaction (ORR) is the cornerstone reaction of many renewable energy technologies such as fuel cells and rechargeable metal-air batteries.The Pt-based electrocatalysts exhibit the highest activity toward ORR, but their large implementation is greatly prohibiting by unaffordable cost and inferior durability.During electrode manufacturing and electrochemical reaction, severe aggregation of catalyst nanoparticles induced by size effect further limits the operational performance of electrocatalysts.We report a new strategy for fabrication of active and aggregation-resistant ORR electrocatalyst by caging metal-organic frameworks derived Co-N-C nanocomposites in permeable and porous 3D graphene cages via sprayed drying the mixed colloids of ZIF-67 nanoparticles and graphene oxide, followed by annealing.The 3D graphene cages around Co-N-C nanocomposites not only provide a continuous conductive network for charge transfer, but also prevent the active phase from aggregation during electrode manufacturing and electrochemical reactions.When evaluated as an ORR electrocatalyst, the material exhibited comparable activity but superior stability to commercial Pt/C catalyst in an alkaline electrolyte. © 2018 Chinese Chemical Society. All rights reserved.