Bifunctional earth-abundant phosphate/phosphide catalysts prepared <i>via</i> atomic layer deposition for electrocatalytic water splitting

Rongé, Jan; Dobbelaere, Thomas; Henderick, Lowie; Minjauw, Matthias; Sree, Sreeprasanth Pulinthanathu; Dendooven, Jolien; Martens, Johan A.; Detavernier, Christophe

doi:10.1039/c9na00391f

Cited by 27 publications

(23 citation statements)

References 32 publications

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“…Instead, these films require activation by exposure of the film to a high potential for a long time or by repeatedly cycling the applied potential. 11 − 13 Due to the wide range of employed preparation and activation conditions, the activity of CoPi catalysts reported in the literature is highly inconsistent, 14 − 16 and much remains unknown about the activation process and the nature of these catalysts under operating conditions.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Activation of Atomic Layer-Deposited Cobalt Phosphate Electrocatalysts for Water Oxidation

et al. 2021

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The development of efficient and stable earth-abundant water oxidation catalysts is vital for economically feasible water-splitting systems. Cobalt phosphate (CoPi)-based catalysts belong to the relevant class of nonprecious electrocatalysts studied for the oxygen evolution reaction (OER). In this work, an in-depth investigation of the electrochemical activation of CoPi-based electrocatalysts by cyclic voltammetry (CV) is presented. Atomic layer deposition (ALD) is adopted because it enables the synthesis of CoPi films with cobalt-to-phosphorous ratios between 1.4 and 1.9. It is shown that the pristine chemical composition of the CoPi film strongly influences its OER activity in the early stages of the activation process as well as after prolonged exposure to the electrolyte. The best performing CoPi catalyst, displaying a current density of 3.9 mA cm –2 at 1.8 V versus reversible hydrogen electrode and a Tafel slope of 155 mV/dec at pH 8.0, is selected for an in-depth study of the evolution of its electrochemical properties, chemical composition, and electrochemical active surface area (ECSA) during the activation process. Upon the increase of the number of CV cycles, the OER performance increases, in parallel with the development of a noncatalytic wave in the CV scan, which points out to the reversible oxidation of Co 2+ species to Co 3+ species. X-ray photoelectron spectroscopy and Rutherford backscattering measurements indicate that phosphorous progressively leaches out the CoPi film bulk upon prolonged exposure to the electrolyte. In parallel, the ECSA of the films increases by up to a factor of 40, depending on the initial stoichiometry. The ECSA of the activated CoPi films shows a universal linear correlation with the OER activity for the whole range of CoPi chemical composition. It can be concluded that the adoption of ALD in CoPi-based electrocatalysis enables, next to the well-established control over film growth and properties, to disclose the mechanisms behind the CoPi electrocatalyst activation.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Activation of Atomic Layer-Deposited Cobalt Phosphate Electrocatalysts for Water Oxidation

et al. 2021

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“…The other is to use organophosphorus‐containing ligands as precursors, including O‐phospho‐DL‐serine [13] and phytic acid [15] . Phosphates have been prepared in hydrothermal, [17,18] co‐precipitation, [19,20] solvothermal, [21,22] atomic layer deposition [23] and electrodeposition [24] methods. Phytic acid (PA) is a natural organic phosphorus resource containing six phosphoric acid groups, which can be obtained from plant seeds and grains, and has a strong chelating ability.…”

Section: Introductionmentioning

confidence: 99%

Phytic Acid‐Based FeCo Bimetallic Metal‐Organic Gels for Electrocatalytic Oxygen Evolution Reaction

Feng

Xiao

Huang

et al. 2021

Chemistry An Asian Journal

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Electrocatalysts have been developed to improve the efficiency of gas release for oxygen evolution reaction (OER), and finding a simple and efficient method for efficient electrocatalysts has inspired research enthusiasm. Herein, we report bimetallic metal‐organic gels derived from phytic acid (PA) and mixed transition metal ions to explore their performance in electrocatalytic oxygen evolution reaction. PA is a natural phosphorus‐rich organic compound, which can be obtained from plant seeds and grains. PA reacts with bimetallic ions (Fe3+ and Co2+) in a facile one‐pot synthesis under mild conditions to form PA‐FeCo bimetallic gels, and the corresponding aerogels are further partially reduced with NaBH4 to improve the electrocatalytic activity. Mixed valence states of Fe(II)/Fe(III) and Co(III)/Co(II) are present in the materials. Excellent OER performance in terms of overpotential (257 mV at 20 mA cm−2) and Tafel slope (36 mV dec−1) is achieved in an alkaline electrolyte. This reduction method is superior to the pyrolysis method by well maintaining the gel morphology structure. This strategy is conducive to the further improvement of the performance of metal‐organic electrocatalysts, and provides guidance for the subsequent application of metal‐organic gel electrocatalysts.

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“…16,21,27 Very recently, this approach has been used for the preparation of cobalt phosphate/phosphide and iron phosphate/ phosphide layers, applied as bifunctional electrocatalysts for the OER and the hydrogen evolution reaction (HER). 28 In this paper, we address the process development of ALD of CoPi as well as the characterization of the material in terms of optochemical properties in view of its application. Moreover, we infer the surface reactions taking place during the ALD steps to deduce the effect of those on the overall ALD process characteristics.…”

Section: Introductionmentioning

confidence: 99%

Atomic layer deposition of cobalt phosphate from cobaltocene, trimethylphosphate, and O2 plasma

Palma

Knoops

Kessels

et al. 2020

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Bifunctional earth-abundant phosphate/phosphide catalysts prepared via atomic layer deposition for electrocatalytic water splitting

Abstract: The development of active and stable earth-abundant catalysts for hydrogen and oxygen evolution is one of the requirements for successful production of renewable fuels.

Cited by 27 publications

References 32 publications

Electrochemical Activation of Atomic Layer-Deposited Cobalt Phosphate Electrocatalysts for Water Oxidation

Electrochemical Activation of Atomic Layer-Deposited Cobalt Phosphate Electrocatalysts for Water Oxidation

Phytic Acid‐Based FeCo Bimetallic Metal‐Organic Gels for Electrocatalytic Oxygen Evolution Reaction

Atomic layer deposition of cobalt phosphate from cobaltocene, trimethylphosphate, and O2 plasma

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