Balancing the Hydrogen Evolution Reaction, Surface Energetics, and Stability of Metallic MoS2 Nanosheets via Covalent Functionalization
Balancing the Hydrogen Evolution Reaction, Surface Energetics, and Stability of Metallic MoS2 Nanosheets via Covalent Functionalization
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DOI：
10.1021/jacs.7b11242
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发表时间：
2018-01-10
影响因子：
15
通讯作者：
Miller, Elisa M.
中科院分区：
文献类型：
--
作者：
Benson, Eric E.;Zhang, Hanyu;Miller, Elisa M.
我们通过共价化学官能化来修改二硫化钼（MoS 2）的金属（1 T相）纳米片的基本电子性质，从而直接影响析氢反应（HER）的动力学、表面能量学和稳定性。化学剥离的金属MoS 2纳米片用含有给电子或吸电子基团的有机苯环官能化。我们发现用最多给电子官能团（p-（CH 3CH 2）（2）NPh-MoS 2）官能化的MoS 2是该系列中用于HER的最有效的催化剂，其初始活性与原始金属相的MoS 2相比稍差。p-（CH 3CH 2）（2）NPh-MoS 2比未官能化的金属MoS 2更稳定，并且在相同条件下在10 min内连续放出H-2的性能优于未官能化的金属MoS 2。关于整个研究系列，催化HER的过电位和塔菲尔斜率都与官能团的供电子强度直接相关。结果是一致的机制，涉及基态电子捐赠或撤回到/从二硫化钼纳米片，这修改了电子转移动力学和催化活性的二硫化钼纳米片。官能团保留了MoS 2纳米片的金属性质，当在氮气气氛中温和退火时，抑制转化为结晶稳定的半导体状态（2 H）。我们建议，电子密度，因此，二硫化钼纳米片的反应性是由所连接的官能团控制。MoS 2和其他过渡金属二硫属化物的官能化纳米片提供了用于控制传统热不稳定金属状态内的电子性质和稳定性的合成化学路线。
We modify the fundamental electronic properties of metallic (1T phase) nanosheets of molybdenum disulfide (MoS2) through covalent chemical functionalization, and thereby directly influence the kinetics of the hydrogen evolution reaction (HER), surface energetics, and stability. Chemically exfoliated, metallic MoS2 nanosheets are functionalized with organic phenyl rings containing electron donating or withdrawing groups. We find that MoS2 functionalized with the most electron donating functional group (p-(CH3CH2)(2)NPh-MoS2) is the most efficient catalyst for HER in this series, with initial activity that is slightly worse compared to the pristine metallic phase of MoS2. The p-(CH3CH2)(2)NPh-MoS2 is more stable than unfunctionalized metallic MoS2 and outperforms unfunctionalized metallic MoS2 for continuous H-2 evolution within 10 min under the same conditions. With regards to the entire studied series, the overpotential and Tafel slope for catalytic HER are both directly correlated with the electron donating strength of the functional group. The results are consistent with a mechanism involving ground-state electron donation or withdrawal to/from the MoS2 nanosheets, which modifies the electron transfer kinetics and catalytic activity of the MoS2 nanosheet. The functional groups preserve the metallic nature of the MoS2 nanosheets, inhibiting conversion to the thermodynamically stable semiconducting state (2H) when mildly annealed in a nitrogen atmosphere. We propose that the electron density and, therefore, reactivity of the MoS2 nanosheets are controlled by the attached functional groups. Functionalizing nanosheets of MoS2 and other transition metal dichalcogenides provides a synthetic chemical route for controlling the electronic properties and stability within the traditionally thermally unstable metallic state.