Research Group Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
J Am Chem Soc. 2013 Aug 7;135(31):11550-61. doi: 10.1021/ja402598k. Epub 2013 Jul 17.
The early stages of nanocrystal nucleation and growth are still an active field of research and remain unrevealed. In this work, by the combination of aberration-corrected transmission electron microscopy (TEM) and electrochemical characterization of the electrodeposition of different metals, we provide a complete reformulation of the Volmer-Weber 3D island growth mechanism, which has always been accepted to explain the early stages of metal electrodeposition and thin-film growth on low-energy substrates. We have developed a Generalized Electrochemical Aggregative Growth Mechanism which mimics the atomistic processes during the early stages of thin-film growth, by incorporating nanoclusters as building blocks. We discuss the influence of new processes such as nanocluster self-limiting growth, surface diffusion, aggregation, and coalescence on the growth mechanism and morphology of the resulting nanostructures. Self-limiting growth mechanisms hinder nanocluster growth and favor coalescence driven growth. The size of the primary nanoclusters is independent of the applied potential and deposition time. The balance between nucleation, nanocluster surface diffusion, and coalescence depends on the material and the overpotential, and influences strongly the morphology of the deposits. A small extent of coalescence leads to ultraporous dendritic structures, large surface coverage, and small particle size. Contrarily, full recrystallization leads to larger hemispherical monocrystalline islands and smaller particle density. The mechanism we propose represents a scientific breakthrough from the fundamental point of view and indicates that achieving the right balance between nucleation, self-limiting growth, cluster surface diffusion, and coalescence is essential and opens new, exciting possibilities to build up enhanced supported nanostructures using nanoclusters as building blocks.
纳米晶体成核和生长的早期阶段仍然是一个活跃的研究领域，尚未被揭示。在这项工作中，通过结合具有像差校正的透射电子显微镜（TEM）和电化学研究不同金属的电沉积，我们对一直以来被接受的用于解释金属电沉积和低能衬底上薄膜生长早期阶段的Volmer-Weber 3D 岛状生长机制进行了完整的重新表述。我们开发了一种广义的电化学聚集生长机制，通过将纳米团簇作为构建块，模拟了薄膜生长早期阶段的原子过程。我们讨论了新过程（如纳米团簇自限制生长、表面扩散、聚集和聚结）对生长机制和所得纳米结构形貌的影响。自限制生长机制阻碍了纳米团簇的生长并有利于团聚驱动的生长。初级纳米团簇的尺寸与施加的电势和沉积时间无关。成核、纳米团簇表面扩散和聚结之间的平衡取决于材料和过电势，并且强烈影响沉积物的形貌。适度的聚结会导致超多孔树枝状结构、大的表面覆盖率和小的颗粒尺寸。相反，完全再结晶会导致更大的半球单晶岛和更小的颗粒密度。我们提出的机制从根本上代表了一个科学突破，并表明在成核、自限制生长、团簇表面扩散和聚结之间取得正确平衡是至关重要的，并且为使用纳米团簇作为构建块构建增强型负载纳米结构开辟了新的令人兴奋的可能性。
