Surface Modifications of Ti2 CO2 for Obtaining High Hydrogen Evolution Reaction Activity and Conductivity: A Computational Approach.
Surface Modifications of Ti2 CO2 for Obtaining High Hydrogen Evolution Reaction Activity and Conductivity: A Computational Approach.
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DOI：
10.1002/cphc.201800899
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发表时间：
2018-11
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影响因子：
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通讯作者：
Shuo Wang;Liang Chen;Yang Wu;Qiuju Zhang
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文献类型：
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作者：
Shuo Wang;Liang Chen;Yang Wu;Qiuju Zhang
开发高电导率、高活性的析氢反应催化剂是可再生能源开发的重中之重。氧封端的Ti2C（Ti2CO2）作为一种典型的MXene，在低氢覆盖率下表现出良好的HER Gibbs自由能（Δ GH），但其约1.0eV的大带隙限制了其导电能力。通过掺杂磷（P）或硫（S）来部分取代表面氧，使不同氢覆盖率下的平均自由能（Δ GHa）都趋近于零，同时电导率也得到显著提高，禁带宽度减小到0.3eV以下.部分电荷分析表明，表面掺杂P或S会引起O2px上的电子向O2pz扩散，导致O2pz与H1s反应. H1s与O2pz的面重叠将增强结合强度，从而降低Δ GH。掺杂P或S后，Ti 3d能级向费米能级移动，使带隙减小，电导率提高。通过引入表面氧空位和磷空位，研究了空位效应对HER性能的影响，发现空位效应不仅提高了Δ GHa和电导率，而且降低了H2O裂解反应势垒（<0.2eV）。扶手椅型纳米粒子（ANR）通过50%的P掺杂显示出改善的HER活性。我们的研究表明，对MXene进行端基修饰可以有效提高其HER催化活性和电导率，有望促进其在电催化和能量转换方面的潜在应用。
The identification of hydrogen evolution reaction (HER) catalysts with high conductivity and high activity is the top priority in the development of renewable energy. Oxygen-terminated Ti2 C (Ti2 CO2 ), as one of the typical MXenes, shows good HER Gibbs free energy (ΔGH ) at low hydrogen coverage, whereas the large band gap of approximately 1.0 eV limits its conductivity capability. By doping phosphor (P) or sulfur (S) to partially substitute the surficial O, the average free energy (ΔGH a ) at various hydrogen coverages has been draggd to approach zero, and the conductivity is also significantly improved by narrowing the band gap to lower than 0.3 eV. Partial charge analysis indicates that doping P or S on the surface induces the diffusion of electrons on oxygen from O 2px to O 2pz , resulting in O 2pz reaction with H 1s. The facial overlapping of H 1s with O 2pz will strengthen the binding strength, hence lowering ΔGH . The energy shift toward Fermi level of Ti 3d after P or S doping contributes to the reduced band gap and high conductivity. Surficial O or P vacancies are created to evaluate the vacancy effect on HER performance, which not only improves ΔGH a and conductivity but also leads to a low reaction barrier of H2 O splitting (<0.2 eV). The armchair nanoribbon (ANR) displays improved HER activity by P-doping at 50% ratio. Our research shows that modification of end-group in MXenes can effectively improve HER catalytic activity and conductivity, which is expected to promote their potential applications in electrocatalysis and energy conversion.