TY - JOUR
T1 - Systematic investigation of anode catalysts for liquid ammonia electrolysis
AU - Akagi, Natsuho
AU - Hori, Keisuke
AU - Sugime, Hisashi
AU - Noda, Suguru
AU - Hanada, Nobuko
N1 - Funding Information:
This work has been partially supported by Japan Society for Promotion of Science (JSPS) under “Grant-in-Aid for Young Scientists (B) (16K18255)” and a Waseda University Grant for Special Research Projects (Project number: 2020R-031). The authors thank Bozhi Chen, Waseda University for TEM observation. And the authors acknowledge Prof. Toshiyuki Momma, Waseda University for useful discussion about the standard electrode potential of the Pt wire RE. The authors thank Sumire Miyakoshi at Waseda University for ECSA and ICP measurements, and the evaluation of the current efficiency of ammonia electrolysis.
Publisher Copyright:
© 2022 Elsevier Inc.
PY - 2022/2
Y1 - 2022/2
N2 - 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.
AB - 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.
KW - Anode catalysts
KW - Electrolysis
KW - Hydrogen production
KW - Liquid ammonia
KW - Volcano correlation
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U2 - 10.1016/j.jcat.2022.01.005
DO - 10.1016/j.jcat.2022.01.005
M3 - Article
AN - SCOPUS:85124066294
SN - 0021-9517
VL - 406
SP - 222
EP - 230
JO - Journal of Catalysis
JF - Journal of Catalysis
ER -