Wan Jing, Wang Congcong, Tang Qian, Gu Xiao, He Mingquan
Chongqing Key Laboratory of Soft Condensed Matter Physics and Smart Materials, College of Physics, Chongqing University Chongqing 401331 China
School of Physical Science and Technology, Ningbo University Ningbo 315000 China
RSC Adv. 2019 Nov 15;9(64):37467-37473. doi: 10.1039/c9ra06539c. eCollection 2019 Nov 13.
Vanadium carbides have attracted much attention as highly active catalysts in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), while a satisfactory understanding of the underlying mechanisms still remains a challenge. Herein we apply first-principles calculations to systematically analyze the crystal structures, electronic properties, free energies during the HER and OER processes, surface energies and crystal formation energies of the three types of vanadium carbides, , VC, VC and VC. We show that all these vanadium carbides are metallic, which enables efficient electron transport from the bulk to the surface of the catalysts. All these vanadium carbides exhibit excellent HER performance but show poor OER catalytic activity. In particular, the VC (110) surface shows the best catalytic performance for its relatively small |Δ(H*)| value (-0.114 eV) for HER. Emergence of natural carbon vacancies gives rise to large surface energy, proper hydrogen adsorption energy, low crystal formation energy and weak bond strength in VV, which guarantees its leading position among the three vanadium carbides. In addition, a remarkable resemblance between VC/VC and Pt in their electronic structures on (110) and (111) surfaces are found, which indicates a Pt-like HER mechanism in these vanadium carbides. Our results thus bring new insights to the theoretical understanding of the excellent HER performance of vanadium carbides.
碳化钒作为析氢反应（HER）和析氧反应（OER）中高活性催化剂备受关注，然而对其潜在机制的充分理解仍是一项挑战。在此，我们应用第一性原理计算系统地分析了三种碳化钒（ 、VC、VC ）的晶体结构、电子性质、HER和OER过程中的自由能、表面能及晶体形成能。我们表明，所有这些碳化钒都是金属性的，这使得电子能够从体相高效传输至催化剂表面。所有这些碳化钒均展现出优异的HER性能，但OER催化活性较差。特别是，VC（110）表面因其在HER中相对较小的|Δ(H*)|值（-0.114 eV）而表现出最佳的催化性能。天然碳空位的出现导致VV具有较大的表面能、合适的氢吸附能、较低的晶体形成能和较弱的键强度，这保证了它在三种碳化钒中的领先地位。此外，发现VC/VC在（110）和（111）表面的电子结构与Pt有显著相似性，这表明这些碳化钒中存在类似Pt的HER机制。因此，我们的结果为碳化钒优异HER性能的理论理解带来了新的见解。
