New Insight into the Mechanism of the Hydrogen Evolution Reaction on MoP(001) from First Principles

Yayun Zhang, Hanwu Lei, Dengle Duan, Elmar Villota, Chao Liu, Roger Ruan

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Molybdenum phosphide-based catalysts have recently exhibited excellent catalytic activities for the hydrogen evolution reaction (HER) in wide pH range conditions; the intrinsic reaction mechanism, on the other hand, has not been well established. Herein, by employing the MoP as the prototypical molybdenum phosphide-based catalyst, HER activities in both acid and neutral conditions were studied by conducting periodic density functional theory calculations. Thermodynamic analysis of hydrogen atoms absorbed on both P- and Mo-terminated surfaces were compared, as well as all the reaction energy and activation energy barriers for reactions involved in the HER process. Calculation results revealed that, in an acid condition, the Volmer-Heyrovsky and Volmer-Tafel reaction mechanisms were dominated on the P-terminated and Mo-terminated catalyst surfaces, where Heyrovsky and Volmer reactions were the rate-determining step, respectively. Additionally, water splitting was introduced to the current reaction mechanism and a small reaction activation energy barrier was revealed on the P-terminated surface. Besides, a relevant small activation energy was obtained in the Tafel reaction on the defect of the P-terminated surface in a neutral solution. Theoretical results proved that HER could take place readily on both P- and Mo-terminated catalyst surfaces via different reaction mechanisms in the acid condition from the view of atom scale. More important, computational results uncovered that HER could also occur on the P-terminated surface with the assistance of surface defect in the neutral condition, which sheds new light on the HER mechanism on transition metal phosphite-based catalysts. The doping effect on HER activity was further investigated in theory and calculation results, indicating that catalytic performance could be improved by substitutional doping of the Mo atom with metals such as Mn and W.

Original languageEnglish (US)
Pages (from-to)20429-20439
Number of pages11
JournalACS Applied Materials and Interfaces
Volume10
Issue number24
DOIs
StatePublished - Jun 20 2018

Keywords

  • MoP(001)
  • catalytic reaction mechanism
  • hydrogen evolution reaction
  • substitutional doping
  • surface defect
  • water splitting reaction

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