Liu Yang, Zhang Hanguang, Behara Pavan Kumar, Wang Xiaoyu, Zhu Dewei, Ding Shuo, Ganesh Sai Prasad, Dupuis Michel, Wu Gang, Swihart Mark T
Department of Chemical and Biological Engineering , University at Buffalo , Buffalo , New York 14260 , United States.
Computational and Data-Enabled Science and Engineering Program , The State University of New York Buffalo , Buffalo , New York 14260 , United States.
ACS Appl Mater Interfaces. 2018 Dec 12;10(49):42417-42426. doi: 10.1021/acsami.8b15895. Epub 2018 Nov 30.
Size- and shape-dependent electrochemical activity of nanostructures reveals relationships between nanostructure design and electrochemical performance. However, electrochemical performance of aspect-ratio-tunable quasi-two-dimensional (2D) nanomaterials with anisotropic properties has not been fully investigated. We prepared monodispersed hexagonal covellite (CuS) nanoplatelets (NPls) of fixed thickness (∼2 nm) but broadly tunable diameter (from 8 to >100 nm). These span a range of aspect ratios, from ∼4 to >50, connecting quasi-isotropic and quasi-2D regimes. Tests of electrochemical activity of the NPls for the oxygen reduction reaction in alkaline solution showed improved activity with increasing diameter. Combining experimental results with density functional theory calculations, we attribute size-dependent enhancement to anisotropy of conductivity and electrochemical activity. The lowest computed oxygen adsorption energy was on Cu sites exposed by cleaving covellite along (001) planes through tetrahedrally coordinated Cu atoms. The specific surface area of these planes, which are the top and bottom surfaces of the NPls, remains constant with changing diameter, for fixed NPl thickness. However, charge transport through the electrocatalyst film improves with increasing NPl diameter. These CuS NPl-carbon nanocatalysts provide inspiration for creating well-controlled layered nanomaterials for electrochemical applications and open up opportunities to design new electrocatalysts using transition-metal sulfides.
纳米结构的尺寸和形状依赖性电化学活性揭示了纳米结构设计与电化学性能之间的关系。然而，具有各向异性的纵横比可调准二维（2D）纳米材料的电化学性能尚未得到充分研究。我们制备了厚度固定（约2 nm）但直径可广泛调节（从8到>100 nm）的单分散六方纤锌矿型硫化铜（CuS）纳米片（NPls）。这些纳米片的纵横比范围从约4到>50，连接了准各向同性和准二维区域。对NPls在碱性溶液中氧还原反应的电化学活性测试表明，活性随直径增加而提高。将实验结果与密度泛函理论计算相结合，我们将尺寸依赖性增强归因于电导率和电化学活性的各向异性。计算得出的最低氧吸附能位于通过四面体配位的铜原子沿（001）面劈开纤锌矿型硫化铜而暴露的铜位点上。对于固定的NPl厚度，这些作为NPls顶面和底面的平面的比表面积在直径变化时保持不变。然而，通过电催化剂膜的电荷传输随着NPl直径的增加而改善。这些CuS NPl-碳纳米催化剂为制备用于电化学应用的可控层状纳米材料提供了灵感，并为使用过渡金属硫化物设计新型电催化剂开辟了机会。
