Moderate heat treatment of CoFe Prussian blue analogues for enhanced oxygen evolution reaction performance

Fangyuan Diao, Mikkel Rykær Kraglund, Huili Cao, Xiaomei Yan, Pei Liu, Christian Engelbrekt*, Xinxin Xiao*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Prussian blue analogues (PBAs) with inherent ordered structures and abundant metal ion sites are widely explored as precursors for various electrochemical applications, including oxygen evolution reaction (OER). Using a range of characterization techniques including Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), this work discloses the process of replacement of K+ by NH4+ in the interstitial spaces of the CoFe PBA by a hot aqueous urea solution, which influences the transformation of PBAs under further heat treatment and the OER performance of the derivatives. After heat treatment at 400 ℃ under Ar flow, high-resolution transmission electron microscopy (HRTEM) images reveal that CoFe alloy nanoparticles grew on the crystalline cubes of CoFe PBA with K+, while CoFe PBA cubes with NH4+ become amorphous. Besides, the derivative of CoFe PBA with NH4+ (Ar-U-CoFe PBA) performs better than the derivative of CoFe PBA with K+ (Ar-CoFe PBA) in OER, registering a lower overpotential of 305 mV at 10 mA cm−2, a smaller Tafel slope of 36.1 mV·dec−1, and better stability over a testing course of 20 h in 1.0 M KOH. A single-cell alkaline electrolyzer, using Ar-U-CoFe PBA and Pt/C, requires an initial cell voltage of 1.66 V to achieve 100 mA cm−2 at 80 ℃, with negligible degradation after 100 h.
Original languageEnglish
JournalJournal of Energy Chemistry
Pages (from-to)476-486
ISSN2095-4956
DOIs
Publication statusPublished - 2023

Keywords

  • Prussian blue analogues
  • PBA derivatives
  • Oxygen evolution reaction
  • Electrolyzer

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