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      Catalysts for hydrogen evolution from the [NiFe] hydrogenase to the Ni2P(001) surface: the importance of ensemble effect.

      1 ,
      Journal of the American Chemical Society
      American Chemical Society (ACS)

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          Abstract

          Density functional theory (DFT) was employed to investigate the behavior of a series of catalysts used in the hydrogen evolution reaction (HER, 2H(+) + 2e(-) --> H(2)). The kinetics of the HER was studied on the [NiFe] hydrogenase, the [Ni(PS3*)(CO)](1)(-) and [Ni(PNP)(2)](2+) complexes, and surfaces such as Ni(111), Pt(111), or Ni(2)P(001). Our results show that the [NiFe] hydrogenase exhibits the highest activity toward the HER, followed by [Ni(PNP)(2)](2+) > Ni(2)P > [Ni(PS3*)(CO)](1)(-) > Pt > Ni in a decreasing sequence. The slow kinetics of the HER on the surfaces is due to the fact that the metal hollow sites bond hydrogen too strongly to allow the facile removal of H(2). In fact, the strong H-Ni interaction on Ni(2)P(001) can lead to poisoning of the highly active sites of the surface, which enhances the rate of the HER and makes it comparable to that of the [NiFe] hydrogenase. In contrast, the promotional effect of H-poisoning on the HER on Pt and Ni surfaces is relatively small. Our calculations suggest that among all of the systems investigated, Ni(2)P should be the best practical catalyst for the HER, combining the high thermostability of the surfaces and high catalytic activity of the [NiFe] hydrogenase. The good behavior of Ni(2)P(001) toward the HER is found to be associated with an ensemble effect, where the number of active Ni sites is decreased due to presence of P, which leads to moderate bonding of the intermediates and products with the surface. In addition, the P sites are not simple spectators and directly participate in the HER.

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          Author and article information

          Journal
          J Am Chem Soc
          Journal of the American Chemical Society
          American Chemical Society (ACS)
          0002-7863
          0002-7863
          Oct 26 2005
          : 127
          : 42
          Affiliations
          [1 ] Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, USA.
          Article
          10.1021/ja0540019
          16231942
          560f3843-54a1-48c0-a81c-f942bde86da2
          History

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