Zhao Lu, Zhang Yun, Zhao Zhonglong, Zhang Qing-Hua, Huang Lin-Bo, Gu Lin, Lu Gang, Hu Jin-Song, Wan Li-Jun
Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Natl Sci Rev. 2020 Jan;7(1):27-36. doi: 10.1093/nsr/nwz145. Epub 2019 Oct 1.
Alkaline hydrogen evolution reaction (HER), consisting of Volmer and Heyrovsky/Tafel steps, requires extra energy for water dissociation, leading to more sluggish kinetics than acidic HER. Despite the advances in electrocatalysts, how to combine active sites to synergistically promote both steps and understand the underlying mechanism remain largely unexplored. Here, Density Functional Theory (DFT) calculations predict that NiO accelerates the Volmer step while metallic Ni facilitates the Heyrovsky/Tafel step. A facile strategy is thus developed to control Ni/NiO heterosurfaces in uniform and well-dispersed Ni-based nanocrystals, targeting both reaction steps synergistically. By systematically modulating the surface composition, we find that steering the elementary steps through tuning the Ni/NiO ratio can significantly enhance alkaline HER activity, and Ni/NiO nanocrystals with a Ni/NiO ratio of 23.7% deliver the best activity, outperforming other state-of-the-art analogues. The results suggest that integrating bicomponent active sites for elementary steps is effective for promoting alkaline HER, but they have to be balanced.
碱性析氢反应（HER）由Volmer步骤和Heyrovsky/Tafel步骤组成，需要额外的能量来进行水的解离，导致其动力学比酸性HER更缓慢。尽管电催化剂取得了进展，但如何结合活性位点以协同促进这两个步骤并理解其潜在机制在很大程度上仍未得到探索。在这里，密度泛函理论（DFT）计算预测，NiO加速Volmer步骤，而金属Ni促进Heyrovsky/Tafel步骤。因此，开发了一种简便的策略来控制均匀且分散良好的镍基纳米晶体中的Ni/NiO异质表面，协同针对两个反应步骤。通过系统地调节表面组成，我们发现通过调整Ni/NiO比例来控制基本步骤可以显著提高碱性HER活性，并且Ni/NiO比例为23.7%的Ni/NiO纳米晶体表现出最佳活性，优于其他最先进的类似物。结果表明，整合用于基本步骤的双组分活性位点对于促进碱性HER是有效的，但它们必须保持平衡。
