Electrochemical behavior of a Ni3N OER precatalyst in Fe-purified alkaline media: The impact of self-oxidation and Fe incorporation

Kenta Kawashima, Raúl A. Márquez-Montes, Hao Li, Kihyun Shin, Chi L. Cao, Kobe M. Vo, Yoon Jun Son, Bryan R. Wygant, Adithya Chunangad, Duck Hyun Youn, Graeme Henkelman, Víctor H. Ramos-Sánchez, C. Buddie Mullins

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Nickel nitride (Ni3N) is known as one of the promising precatalysts for the electrochemical oxygen evolution reaction (OER) under alkaline conditions. Due to its relatively low oxidation resistance, Ni3N is electrochemically self-oxidized into nickel oxides/oxyhydroxides (electroactive sites) during the OER. However, we lack a full understanding of the effects of Ni3N self-oxidation and Fe impurity incorporation into Ni3N from electrolyte towards OER activity. Here, we report on our examination of the compositional and structural transformation of Ni3N precatalyst layers on Ni foams (Ni3N/Ni foam) during extended periods of OER testing in Fe-purified and unpurified KOH media using both a standard three-electrode cell and a flow cell, and discuss their electrocatalytic properties. After the OER tests in both KOH media, the Ni3N surfaces were converted into amorphous, nano-porous nickel oxide/(oxy)hydroxide surfaces. In the Fe-purified electrolyte, a decrease in OER activity was confirmed after the OER test because of the formation of pure NiOOH with low OER activity and electrical conductivity. Conversely, in the unpurified electrolyte, a continuous increase in OER activity was observed over the OER testing, which may have resulted from the Fe incorporation into the self-oxidation-formed NiOOH. Our experimental findings revealed that Fe impurities play an essential role in obtaining notable OER activity using the Ni3N precatalyst. Additionally, our Ni3N/Ni foam electrode exhibited a low OER overpotential of 262 mV to reach a geometric current density of 10 mA cmgeo-2 in a flow cell with unpurified electrolyte.

Original languageEnglish (US)
Pages (from-to)2299-2309
Number of pages11
JournalMaterials Advances
Volume2
Issue number7
DOIs
StatePublished - Apr 7 2021
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • General Materials Science

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