Systematic investigation of anode catalysts for liquid ammonia electrolysis

Natsuho Akagi, Keisuke Hori, Hisashi Sugime, Suguru Noda, Nobuko Hanada*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Liquid ammonia is able to release hydrogen via electrolysis with a theoretical voltage of 0.077 V. However, the actual operation voltage is much higher (around 1–2 V) due to the large overpotential of the anodic reaction. We systematically investigated Pt, Ir, Ru, Ni, Co, Fe, Ta, and Ti as the anodic catalyst, and observed a volcano correlation when plotting the current density against the formation enthalpy of metal nitrides per nitrogen ΔfHMN (kJ/mol-N). ΔfHMN reflects the strength of metal-nitrogen bond, and Ru having a moderate ΔfHMN showed the highest catalytic activity. Then, the activity enhancement via microstructure control was examined. The sputtered Pt and Ni films having a columnar structure with a rough surface showed 7- and 13-times higher current density than the Pt and Ni plates, respectively. An anodic current density of 0.45 mA/cm2 was achieved for the sputtered Ni film at an anodic potential as low as 0.3 V vs H2/NH3.

Original languageEnglish
Pages (from-to)222-230
Number of pages9
JournalJournal of Catalysis
Volume406
DOIs
Publication statusPublished - 2022 Feb

Keywords

  • Anode catalysts
  • Electrolysis
  • Hydrogen production
  • Liquid ammonia
  • Volcano correlation

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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