open access publication

Article, 2023

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

In: Journal of Energy Chemistry, ISSN 2095-4956, Volume 78, Pages 476-486, 10.1016/j.jechem.2022.11.050

Contributors (7)

Diao, Fangyuan [1] Kraglund, Mikkel Rykaer (0000-0002-1229-1007) [1] Cao, Huili (0000-0001-8632-0969) [1] Yan, Xiaomei (0000-0003-1882-4713) [1] Liu, Pei [1] Engelbrekt, Christian (0000-0003-3679-3666) (Corresponding author) [1] Xiao, Xinxin (0000-0002-0240-0038) (Corresponding author) [1] [2]

Affiliations

  1. [1] Technical University of Denmark
  2. [NORA names: DTU Technical University of Denmark; University; Denmark; Europe, EU; Nordic; OECD]
  3. [2] Aalborg University
  4. [NORA names: AAU Aalborg University; University; Denmark; Europe, EU; Nordic; OECD]

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 °C 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 for the anodic and cathodic catalyst, respectively, requires an initial cell voltage of 1.66 V to achieve 100 mA cm−2 at 80 °C, with negligible degradation after 100 h.

Keywords

Ar flow, CoFe, CoFe Prussian blue analogues, KOH, M KOH, NH4, OER performance, Prussian blue analogues, Pt/C, Tafel slope, X-ray diffraction, X-ray photoelectron spectroscopy, alkaline electrolyzer, analogues, applications, aqueous urea solutions, blue analogues, catalyst, cathodic catalyst, cell voltage, characterization techniques, course, crystalline cubes, cube, degradation, derivatives, diffraction, dispersive spectroscopy, electrochemical applications, electrolyzer, electron microscopy images, energy dispersive spectroscopy, evolution reaction, evolution reaction performance, flow, further heat treatment, good stability, heat treatment, high-resolution transmission electron microscopy images, images, initial cell voltage, interstitial space, ion sites, low overpotential, mV, metal ion sites, microscopy images, moderate heat treatment, nanoparticles, negligible degradation, overpotential, oxygen evolution reaction, oxygen evolution reaction performance, performance, photoelectron spectroscopy, precursors, process, process of replacement, range, reaction, reaction performance, replacement, sites, slope, small Tafel slope, solution, space, spectroscopy, stability, structure, technique, testing course, transformation, transmission electron microscopy images, treatment, urea solution, voltage, work

Funders

  • China Scholarship Council