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首页> 外文期刊>Catalysis science & technology >The joint effect of electrical conductivity and surface oxygen functionalities of carbon supports on the oxygen reduction reaction studied over bare supports and Mn-Co spinel/carbon catalysts in alkaline media
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The joint effect of electrical conductivity and surface oxygen functionalities of carbon supports on the oxygen reduction reaction studied over bare supports and Mn-Co spinel/carbon catalysts in alkaline media

机译：导电性的联合效应表面的碳氧功能支持氧还原反应的研究裸露的支持和Mn-Co尖晶石/碳催化剂在碱性介质

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摘要

Supported manganese-cobalt spinel catalysts and the corresponding mesoporous carbon supports were examined in order to reveal the effect of electrical conductivity and surface oxygen functionalities on the oxygen reduction reaction (ORR) in alkaline media. Carbon replicas of comparable porosity were obtained from sucrose by nano-replication of a silica template followed by carbonization at different temperatures (650-1050 degrees C). The degree of their graphitization was assessed by deconvolution of the Raman spectra (1000-1800 cm(-1)), whereas relative electrical conductivity measurements were performed by means of the contactless microwave cavity quality factor perturbation technique. The electrocatalytic activities of the obtained materials towards the ORR (gauged by the ORR onset potential and the number of transferred electrons) were tested in alkaline media using standard hydrodynamic methods. It was found that with increasing carbonization temperature, the electrical conductivity of the examined carbon materials increased, in parallel with their growing crystallinity. For the carbon samples calcined in the temperature range 650-850 degrees C, the ORR onset potential initially rises as the electrical conductivity increases, passes through a maximum at around 850 degrees C, and then falls. Such a volcano-type shape was found also in the case of manganese-cobalt spinel catalysts deposited on the examined carbon supports. The observed non-monotonous electrocatalytic behavior was accounted for by two descriptors: the carbon support electrical conductivity and the amount of surface carbonyl and quinone groups, changing in the opposite way with the carbonization temperature. It was shown that variation of the electrical conductivity multiplied by the amount of carboxyl and quinone groups with the carbon calcination temperature exhibits the same behavior as the number of electrons exchanged in the ORR, confirming that an optimal conjunction of these properties plays a decisive role. The prime advantage of the dispersed spinel active phase lies in a significant enhancement of the 4-electron reduction pathway. To the best of our knowledge, the role of electrical conductivity and the nature of the surface oxygen-bearing functional groups in the ORR were elucidated for the first time.
机译：钴锰尖晶石催化剂和支持相应的介孔碳支持检查是为了揭示的效果电导率和表面的氧气功能上的氧还原反应(ORR)在碱性介质。类似的孔隙度从蔗糖中获得的其次是nano-replication的硅模板在不同温度(650 - 1050年碳化度),其石墨化程度反褶积是评估的拉曼吗光谱(1000 - 1800厘米(1)),而相对的电导率测量通过非接触式微波执行的腔品质因数摄动技术。electrocatalytic活动获得的材料向奥尔(测量由奥尔爆发潜力和转移的数量电子)碱性介质中进行了测试标准水动力的方法。随着碳化温度,碳导电性的研究材料增加,并行的结晶度增加。煅烧温度范围650 - 850度C,奥尔发病最初上涨的潜力导电性增加,穿过最多在850摄氏度左右,然后瀑布。在钴锰尖晶石催化剂沉积在研究碳支持。观察non-monotonous electrocatalytic行为占了两个描述符:碳呢导电性和支持羰基和醌组织表面,改变与碳化相反的方向温度。导电率乘以数量羧基和醌团体的碳煅烧温度的展品是一样的行为的电子交换数量奥尔,确认一个最佳的结合的这些性质起着决定性的作用。主要利用分散的尖晶石活跃阶段是一个重要的增强4电还原途径。知识,导电性的作用和表面含氧的性质官能团或者被阐明这已经不是第一次了。

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