Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Wollongong, NSW 2522, Australia.
Nanoscale. 2018 Oct 18;10(40):19074-19081. doi: 10.1039/c8nr07045h.
Constructing heterostructures is an effective strategy for designing efficient electrocatalysts. MoS2 is a star catalyst for hydrogen evolution reaction (HER) in acidic media; however, the alkaline HER activity is deficient due to the sluggish water dissociation process. Herein, Ni(OH)2/MoS2 heterostructures with Ni(OH)2 nanoclusters epitaxially decorated on the surface of MoS2 are synthesized towards the alkaline HER. As compared with MoS2, the epitaxial Ni(OH)2/MoS2 heterostructures show significantly enhanced HER activity in 1 M KOH, and the overpotential is decreased by nearly 150 mV to reach a current density of 10 mA cm-2. The substantial increase in turnover frequency (TOF) demonstrates that the intrinsic activity is greatly improved after the incorporation of Ni(OH)2 nanoclusters. The presence of Ni(OH)2 nanoclusters would provide additional water dissociation sites while MoS2 is ready for the adsorption and combination of the generated H*, and this so-called synergistic effect eventually induces significantly enhanced alkaline HER kinetics. Besides, the electron transfer from Ni(OH)2 to MoS2 increases the proton affinity of MoS2. The present results describe an interesting case of an atomic-scale electrochemically inert material promoted HER process, and would open a new avenue into designing efficient hetero-nanostructures towards electrocatalytic applications.
构建异质结构是设计高效电催化剂的有效策略。MoS2 是酸性介质中析氢反应（HER）的明星催化剂；然而，由于水离解过程缓慢，碱性 HER 活性不足。在此，通过在 MoS2 表面外延生长 Ni(OH)2 纳米簇，合成了用于碱性 HER 的 Ni(OH)2/MoS2 异质结构。与 MoS2 相比，外延生长的 Ni(OH)2/MoS2 异质结构在 1 M KOH 中表现出显著增强的 HER 活性，过电位降低近 150 mV 即可达到 10 mA cm-2 的电流密度。周转频率（TOF）的大幅增加表明，在掺入 Ni(OH)2 纳米簇后，本征活性得到了极大提高。Ni(OH)2 纳米簇的存在提供了额外的水离解位点，而 MoS2 则准备好吸附和结合生成的 H*，这种所谓的协同效应最终导致碱性 HER 动力学得到显著增强。此外，电子从 Ni(OH)2 转移到 MoS2 增加了 MoS2 的质子亲和力。本研究结果描述了一种有趣的原子尺度上电化学惰性材料促进 HER 过程的情况，为设计用于电催化应用的高效异质纳米结构开辟了新途径。
