General trends in Horiuti-Polanyi mechanism vs non-Horiuti-Polanyi mechanism for water formation on transition metal surfaces

Xitong Sun, Jianfu Chen, P. Hu*

*Corresponding author for this work

Research output: Contribution to journalArticle


It is generally acknowledged in heterogeneous catalysis that hydrogenation follows the so-called Horiuti-Polanyi (HP) mechanism. In this work, a thorough investigation of the mechanism of hydrogenation of hydroxyl groups and O catalyzed by a series of transition metals was carried out through density functional theory calculations, as surface hydroxyls and O are very common species in many catalytic systems. It is found that different metal catalysts exhibit different mechanisms. On some metal catalysts, the non-HP mechanism is preferred, whereas the classic HP mechanism is favored on other catalysts. Detailed analyses of the metal-dependent mechanism shows that the activity toward the dissociation of H2 decides which mechanism is preferred. On active catalysts, such as Ni and Pt, H2 prefers to dissociate with strong H adsorption energies, which lead to the classic HP mechanism being favored. On inactive surfaces, on the other hand, the adsorption of H is weak, which results in the non-HP mechanism being preferred. The parameter η, which is a structural descriptor, was defined to understand the different mechanisms.

Original languageEnglish
Pages (from-to)294-301
JournalChinese journal of catalysis
Issue number2
Early online date26 Dec 2019
Publication statusPublished - 01 Feb 2020



  • Density functional theory
  • Horiuti-Polanyi mechanism
  • Hydrogenation
  • Transition metal
  • Water formation

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