Role of Oxygen Vacancy Defects in the Electrocatalytic Activity of Substoichiometric Molybdenum Oxide
Role of Oxygen Vacancy Defects in the Electrocatalytic Activity of Substoichiometric Molybdenum Oxide
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DOI：
10.1021/acs.jpcc.8b03536
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发表时间：
2018-08-16
影响因子：
3.7
通讯作者：
Pettes, Michael Thompson
中科院分区：
文献类型：
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作者：
Kashfi-Sadabad, Raana;Yazdani, Sajad;Pettes, Michael Thompson
介孔α-MoO 3-x与聚（二烯丙基二甲基氯化铵）-官能化的还原氧化石墨烯（PDDA-rGO）组合被引入作为廉价且高效的氧还原反应（ORR）催化剂。介孔催化剂通过由PDDA介导的静电相互作用被导电rGO片包裹。PDDA与MoO 3的热相互作用在400- Time（6）600 ℃下有效地将金属氧化物还原为MoO 3-x，产生表面氧空位。通过密度泛函理论和实验相结合，确定了MoO 3-x表面氧空位在ORR活性中的作用。首次计算了无氧空位的MoO_3和表面有氧空位的MoO（3-x）在每一步的势垒。结果表明，Mo ~（4+）-v（O）（center dot center dot）氧空位的存在显著降低了反应途径中的能垒。该催化剂的过电位为0.86 V（相对于可逆氢电极），具有良好的电化学稳定性，17 h后活性仅下降9%。这些结果提供了一个新的范例，在缺陷工程的金属氧化物与潜在的合成稳定和活性的贵金属无ORR电催化剂。
Mesoporous alpha-MoO3-x combined with poly(diallyldimethylammonium chloride)-functionalized reduced graphene oxide (PDDA-rGO) is introduced as an inexpensive and efficient oxygen reduction reaction (ORR) catalyst. The mesoporous catalysts are wrapped by conductive rGO sheets via an electrostatic interaction induced by a PDDA polyelectrolyte. The thermal interaction of PDDA with MoO3 efficiently reduces the metal oxide to MoO3-x at 400- Time (6) 600 degrees C, creating a surface oxygen vacancy. Through a combination of density functional theory and experiments, the role of the surface oxygen vacancy sites in the ORR activity of MoO3-x is identified. For the first time, all the energy barriers against ORR are calculated at each step for MoO3 with no oxygen vacancies and MoO(3-x )with surface oxygen vacancies. It is shown that the presence of an Mo4+-v(O)(center dot center dot) oxygen vacancy site on the surface significantly reduces the energy barriers against ORR in the reaction pathways. An overpotential of 0.86 V (vs a reversible hydrogen electrode) with excellent electrochemical stability was obtained with the newly designed catalyst, with only a 9% decrease in the activity after similar to 17 h. These results offer a new paradigm in the defect engineering of metal oxides with a potential for the synthesis of stable and active noble metal-free ORR electrocatalysts.