催化学报 ›› 2020, Vol. 41 ›› Issue (5): 839-846.DOI: 10.1016/S1872-2067(19)63488-1

• 电催化专栏 • 上一篇    下一篇

利用MOF-253衍生氮掺杂碳限域效应促进Pt纳米单晶电催化剂的氧析出反应

Hellen Gabriela Rivera Monestela, Ibrahim Saana Amiinua, Andrés Alvarado Gonzálezb, 蒲宗华a, BibiMaryam Mousavib, 木士春a   

  1. a 武汉理工大学材料复合新技术国家重点实验, 湖北武汉 430070;
    b 武汉理工大学化学化工与生命科学学院, 湖北武汉 430070
  • 收稿日期:2019-10-06 修回日期:2019-11-23 出版日期:2020-05-18 发布日期:2019-12-31
  • 通讯作者: 木士春
  • 基金资助:
    国家自然科学基金(51672204);国家重点研发计划课题(2016YFA0202603).

Robust MOF-253-derived N-doped carbon confinement of Pt single nanocrystal electrocatalysts for oxygen evolution reaction

Hellen Gabriela Rivera Monestela, Ibrahim Saana Amiinua, Andrés Alvarado Gonzálezb, Zonghua Pua, BibiMaryam Mousavib, Shichun Mua   

  1. a State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, Hubei, China;
    b School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, Hubei, China
  • Received:2019-10-06 Revised:2019-11-23 Online:2020-05-18 Published:2019-12-31
  • Contact: S1872-2067(19)63488-1
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (51672204), and the National Key Research and Development Program of China (2016YFA0202603).

摘要: 目前,为了有效解决电化学能量转化反应动力学过程缓慢和商业化应用等问题,需要大力提高催化剂的电催化活性和稳定性,并大幅降低贵金属催化剂的用量.通常,铂(Pt)基催化剂对燃料电池的氧还原反应(ORR)和水电解过程的氢析出反应(HER)表现出很高的活性.然而,对于高效的金属-空气电池和水电解装置,其中的氧析出反应(OER)则需要高活性的非Pt电催化剂来降低电化学过电位及提高其对高电位的耐受性.虽然相较于Pt催化剂,IrO2和RuO2等贵金属催化剂表现出了更高的OER活性,然而,它们的稳定性差,难以满足实际应用需求,严重阻碍了其在金属-空气电池和水电解中的应用.通常,Pt对OER的低效催化主要归因于在OER电催化过程中Pt与电解液直接接触,导致Pt表面快速被氧化,形成Pt氧化物(Pt+4O2和Pt+2O)层.形成的Pt氧化物对OER不起催化作用,从而降低了Pt的利用率和总的水电解效率.
为了避免Pt表面的快速氧化,实现高的OER性能,我们将Pt金属纳米粒子有效地限域在超薄功能多孔碳层内.前期,已有大量的有关金属基ORR和HER催化剂研究证明,这种策略对于稳定金属纳米颗粒非常有效,可有效避免金属催化剂的快速氧化,而且还可抑制金属颗粒迁移和团聚;此外,还有利于增强催化剂的导电性和离子物种的扩散能力,从而提高催化剂的电催化性能.然而,要达到提高金属催化剂OER电催化性能的目的,还需要设计一种具有优良结构的功能化异质原子掺杂多孔碳基限域材料.金属有机框架(MOF),特别是MOF-253,由于具有较高的柔韧性、丰富的孔、可控的几何结构和高比表面积,被认为是制备功能多孔碳基限域材料的理想前驱体.
为此,通过结合功能多孔碳基材料的限域作用及MOF-253和超细Pt纳米单晶的优势,本文合成了MOF-253衍生氮掺杂碳(N/C)限域的Pt纳米单晶(Pt@N/C)核壳型电催化剂.制备的Pt-N-C框架不仅具有超薄的氮掺杂活性多孔碳保护层壳体(平均厚度为0.51nm),还有具高度分散和稳定化的Pt纳米单晶核体;值得指出的是,因受到碳层的限域作用,即使经900℃的高温处理,Pt纳米单晶仍保持了较小的晶体尺寸(平均粒径仅为6.7nm);此外,该催化剂的Pt载量较低,仅为6.1wt%(Pt@N/C-10).将其作为OER电催化剂,表现出优异的OER性能:在10mA cm-2电流密度下,其过电位仅为298mV,低于商业IrO2催化剂(353mV);而且,经2000周加速电位扫描后,其电位仅降低19.4mV,也低于IrO2(23.3mV).本文很好地证明了通过构建空间限域结构可以有效解决Pt等金属催化剂因表面氧化而导致OER动力学活性和稳定性低的问题.

关键词: Pt, MOF-253, 碳限域, 氧析出反应, 电催化剂

Abstract: Although carbon-supported platinum (Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), its applications in metal-air batteries as a cathode catalyst, or for oxygen generation via water splitting electrolysis as an anode catalyst is mainly constrained by the insufficient kinetic activity and stability in the oxygen evolution reaction (OER). Here, MOF-253-derived nitrogen-doped carbon (N/C)-confined Pt single nanocrystals (Pt@N/C) have been synthesized and shown to be efficient catalysts for the OER. Even with low Pt mass loading of 6.1 wt% (Pt@N/C-10), the catalyst exhibits greatly improved activity and long-time stability as an efficient OER catalyst. Such high catalytic performance is attributed to the core-shell structure relationship, in which the active N-doped-C shell not only provides a protective shield to avoid rapid Pt nanocrystal oxidation at high potentials and inhibits the Pt migration and agglomeration, but also improves the conductivity and charge transfer kinetics.

Key words: Pt, MOF-253, Carbon confinement, Oxygen evolution reaction, Electrocatalyst