Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China.
Phys Chem Chem Phys. 2018 Jul 25;20(29):19390-19397. doi: 10.1039/c8cp02635a.
MXenes, a new class of two-dimensional materials, arouse great interest due to their diverse chemistries, superior electrical conductivity and stability. Recently, the nanostructures of MXenes such as nanoribbons and nanodots have been synthesized in experiments, which show peculiar properties and expand the application spectrum of MXenes. Here we exploited MXene nanoribbons as potential electrocatalysts for the hydrogen evolution reaction (HER) by considering 12 kinds of MXene systems. Our first-principles calculations showed that the edges of the MXene nanoribbons can adsorb hydrogen species and serve as the reaction sites for hydrogen evolution. The binding strength of the ribbon edge is correlated with the d band center of metal atoms in MXenes. In particular, the nanoribbons of Ti3C2 and solid solution (Ti,Nb)C exhibit high activity for the HER with the adsorption free energy approaching zero and Tafel barrier below 0.42 and 0.17 eV, respectively. The low barrier is owing to the prominent charge transfer from the edge metal atoms to the H* reactants in the transition state. These theoretical results illuminate the principle for designing MXene nanostructures for electrocatalysts with fast kinetics, and shed light on the utilization of MXenes with more than one metal element for a broad range of electrochemical reactions.
MXenes 是一类新型二维材料，由于其多样的化学性质、优异的导电性和稳定性而引起了广泛的关注。最近，MXenes 的纳米结构，如纳米带和纳米点，已经在实验中被合成出来，这些纳米结构表现出了奇特的性质，扩展了 MXenes 的应用范围。在这里，我们考虑了 12 种 MXene 体系，将 MXene 纳米带用作析氢反应 (HER) 的潜在电催化剂。我们的第一性原理计算表明，MXene 纳米带的边缘可以吸附氢物种，并作为析氢反应的反应位点。带边缘的结合强度与 MXenes 中金属原子的 d 带中心有关。特别地，Ti3C2 和固溶体 (Ti,Nb)C 的纳米带对 HER 具有很高的活性，吸附自由能接近零，塔菲尔势垒分别低于 0.42 和 0.17 eV。低势垒归因于在过渡态中，来自边缘金属原子到 H*反应物的显著电荷转移。这些理论结果阐明了设计具有快速动力学的 MXene 纳米结构作为电催化剂的原理，并为利用具有多种金属元素的 MXenes 来进行广泛的电化学反应提供了思路。
