Vacancy-assisted oxygen reduction reaction on cobalt-based catalysts in direct borohydride fuel cell revealed by in-situ XAFS and XRD
Vacancy-assisted oxygen reduction reaction on cobalt-based catalysts in direct borohydride fuel cell revealed by in-situ XAFS and XRD
复制标题
原位 XAFS 和 XRD 揭示直接硼氢化物燃料电池中钴基催化剂上的空位辅助氧还原反应
DOI：
10.1016/j.electacta.2017.09.102
复制
发表时间：
2017
影响因子：
6.6
通讯作者：
Liu Jiabin
中科院分区：
文献类型：
--
作者：
Wang Juan;Lin Longxia;He Yan;Qin Haiying;Yan Shuai;Yang Ke;Li Aiguo;Liu Jiabin
氧还原反应机理是设计新型非铂H2-O2燃料电池电催化剂的关键问题。虽然Men+/Me（n+1）+氧化还原模型已被广泛接受，但在本工作中发现Men+的价态保持不变。采用浸渍-化学法制备了聚吡咯修饰的碳载氢氧化钴催化剂（CoOOH-PPy-BP），并将其用作直接硼氢化物燃料电池的阴极催化剂。CoOOH-PPy-BP具有与Co（OH）2-PPy-BP相容的电化学性能和近4 e的氧转移还原反应。通过原位X射线吸收精细结构（XAFS）和X射线衍射（XRD）分析了放电过程中Co离子周围局域结构的变化。原位XRD未发现新相，原位XAFS检测到氧空位。CoOOH表面的氧空位为O2的吸附提供了有利的位置，加速了O2的活化。由于CoOOH中的氧空位而产生的电子空穴可以从阳极捕获电子以形成激发阳离子态[Co 3 ++ e]。然后通过从[Co 3 ++ e]捕获电子来还原吸收氧分子。提出了一种新的基于氧空位的氧还原反应机理，取代了以前的Con+/Co（n+1）+模型.本工作为通过人为引入氧空位缺陷来设计性能优良的新型催化剂提供了思路。
The oxygen reduction reaction mechanism is the key issue for designing novel non-Pt electrocatalysts of H2-O2fuel cells. Although the Men+/Me(n+1)+redox model has been widely accepted, the valence state of the Men+was found to keep unchanged in this work. Polypyrrole-modified carbon-supported cobalt oxyhydroxide catalyst (CoOOH-PPy-BP) was prepared by impregnation-chemical method and used as cathode catalyst in direct borohydride fuel cells. The CoOOH-PPy-BP exhibited compatible electrochemical properties with Co(OH)2-PPy-BP and a near 4e transfer oxygen reduction reaction. The variation of the local structure around Co ions during discharging was analyzed byin-situX-ray absorption fine structure (XAFS) and X-ray diffraction (XRD) measurements. No new phase was detected byin-situXRD while oxygen vacancies were detected byin-situXAFS. Oxygen vacancies at the surface of CoOOH provided favorable sites for the O2absorption, accelerating the activation of the O2. The electron holes generated due to the oxygen vacancies in the CoOOH can capture electrons from the anode to form excited cationic states [Co3++ e]. Then the absorption oxygen molecule is reduced by capturing electrons from [Co3++ e]. A new oxygen reduction reaction mechanism based on the oxygen vacancy instead of the previous Con+/Co(n+1)+model is proposed. This work provides lights for the design of novel catalysts with excellent performance by introducing defects of oxygen vacancies artificially.