Density functional study of hydrogen evolution on cobalt-embedded carbon nanotubes: effects of doping and surface curvature
Density functional study of hydrogen evolution on cobalt-embedded carbon nanotubes: effects of doping and surface curvature
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钴嵌入碳纳米管析氢的密度泛函研究：掺杂和表面曲率的影响
DOI：
10.1021/acsanm.8b01466
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发表时间：
2018
影响因子：
5.9
通讯作者：
Guo Wenyue
中科院分区：
文献类型：
--
作者：
Zhao Lianming;Guo Sheng;Liu Haijun;Zhu Houyu;Yuan Saifei;Guo Wenyue
探索廉价、高效、稳定的铂基非贵金属催化剂替代物对酸性环境下的析氢反应具有重要意义。先前的实验已经发现，与惰性碳模板或碳-氮材料结合的3d过渡金属Fe、Co和Ni在酸性电解质中表现出长期耐久性和高HER活性。为了阐明决定HER活性的潜在机制，在这里，我们报告了一系列有缺陷的碳纳米管（CNT），掺杂原子Co（CoCNT（n，n），n= 3，5，7，和9）和共掺杂Co和双N（CoN 2CNT（5，5））的HER的理论研究，基于第一性原理密度泛函计算。计算结果表明，Co和Co，N（co）掺杂碳纳米管的HER反应遵循Volmer-Heyrovsky机理，主要活性中心是与金属中心相邻的碳原子. HER活性的提高是由于适当曲率的CNT、Co掺杂以及Co和N共掺杂引起活性C原子的p带中心（εp）升高。CoCNT（n，n）s的HER活性遵循具有表面曲率的火山依赖性，显示出交换电流的近六个数量级的差异，在CoCNT（5，5）处达到峰值，其活性与Pt催化剂相当。在CoCNT（5，5）中掺杂双N原子，交换电流可以进一步显著增强（30倍），甚至比Pt（111）高一个数量级。CoN 2CNT（5，5）的εp（−4.16 eV）非常接近最大交换电流的最佳值（−4.14 eV），这一事实证明了提高CNT HER活性的进步。
Exploring low-cost, efficient, and stable nonprecious alternatives for Pt-based catalysts is of significance in the hydrogen evolution reaction (HER) in acidic environments. Previous experiments have found that 3d transition metals Fe, Co, and Ni incorporated with inert carbon templates or carbon–nitrogen materials exhibit long-term durability and high HER activity in acidic electrolytes. To clarify the underlying mechanism determining the HER activity, here we report a theoretical investigation of the HER on a series of defective carbon nanotubes (CNTs), doped with atomic Co (CoCNT(n,n),n= 3, 5, 7, and 9) and codoped with Co and double N (CoN2CNT(5,5)), based on the first-principle density functional calculations. Our calculations indicate that the HER on these Co- and Co, N-(co)doped CNTs occurs via the Volmer–Heyrovsky mechanism, and the primary active sites are the C atoms adjacent to the metal center. The enhancement of the HER activity is due to uplifting of the p-band center (εp) of the active C atoms induced by using a CNT with appropriate curvature, Co doping, and Co and N codoping. The HER activity of CoCNT(n,n)s follows a volcano dependence with surface curvature, showing nearly six orders of magnitude difference in exchange currents, peaked at CoCNT(5,5), with the activity comparable with Pt-catalysts. Doped with double N atoms in CoCNT(5,5), the exchange current could be further substantially enhanced (by 30 times), even one order of magnitude higher than that of Pt(111). The fact that CoN2CNT(5,5) has an εp(−4.16 eV) very close to the optimum value for the maximum exchange current (−4.14 eV) justifies the advance in improving the HER activity of CNTs.