Deactivation, reactivation and super-activation of Fe-N/C oxygen reduction electrocatalysts: Gas sorption, physical and electrochemical investigation using NO and O2
Deactivation, reactivation and super-activation of Fe-N/C oxygen reduction electrocatalysts: Gas sorption, physical and electrochemical investigation using NO and O2
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DOI：
10.1016/j.apcatb.2021.120169
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发表时间：
2021-04-21
影响因子：
22.1
通讯作者：
Kucernak, Anthony
中科院分区：
文献类型：
--
作者：
Boldrin, Paul;Malko, Daniel;Kucernak, Anthony
结果表明，气态一氧化氮(NO)和氧(O-2)是揭示Fe-N/C催化剂复杂表面过程的有用分子探针。我们揭示了在程序升温脱附实验中使用气态NO和在电化学实验中使用NO(及其前体)之间的区别。气相O-2吸附几乎完全以二氧化碳的形式解吸，持续暴露在氧气中会增加表面化学吸附的氧物种的数量。碳表面的氧化状态是一个重要的活性决定因素，在正常的“电化学”条件下，许多活性中心被阻断。只有在600℃的Ar中处理才能释放这些位置以供氧吸附，然而在大气储存下，特别是在氧还原反应(ORR)中，表面很快就会被化学吸附的氧物种和水失活。我们证明，无论是在电化学三电极电池中还是在燃料电池中，都可以通过还原电化学处理来实现材料的超活化。治疗后获得的能量明显大于能量成本。
We show that gaseous nitric oxide (NO) and oxygen (O-2) are useful molecular probes to uncover complex surface processes in Fe-N/C catalysts. We unravel the difference between using gaseous NO in a temperature programmed desorption experiment and using NO (and progenitors) in an electrochemical experiment. Gas phase O-2 adsorption is almost exclusively desorbed as CO2, and continued exposure to oxygen increases the amount of chemisorbed oxygen species on the surface. The oxidation state of the carbon surface is an important activity determining factor, and under normal "electrochemical" conditions many of the active sites are blocked. Only by treatment at 600 degrees C in Ar can we free those sites for oxygen adsorption, however under atmospheric storage, and especially during the oxygen reduction reaction (ORR), the surface quickly becomes deactivated with chemisorbed oxygen species and water. We demonstrate that the material can be super-activated by reductive electrochemical treatment, both in an electrochemical three electrode cell and in a fuel cell. The energy gained following the treatment is significantly larger than the energetic cost.