Atomic layer deposition of cobalt phosphate thin films for the oxygen evolution reaction

Palma, Valerio Di; Zafeiropoulos, Georgios; Goldsweer, T.; Kessels, W.M.M.; Sanden, M.C.M. van de; Creatore, M.; Tsampas, Mihalis N.

doi:10.1016/j.elecom.2018.11.021

Cited by 25 publications

(26 citation statements)

References 34 publications

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“…FTO served as a substrate for the electrochemical characterization due to its high conductivity and its poor performance as an OER catalyst, which allows us to exclude any contribution from the substrate. 45 As the FTO substrate is textured, all quantities reported here have been normalized to the geometric surface area of the sample, rather than the (unknown) exposed surface area, unless noted otherwise. For a discussion on the details of this normalization procedure, we refer to the experimental section .…”

Section: Results and Discussionmentioning

confidence: 99%

“… 45 In our previous work, we showed that ALD can be used to prepare smooth, amorphous CoPi films with a tunable chemical composition based on the Co/P atomic ratio. 45 In this work, we further exploit the unique capabilities of ALD in order to study the relationship between chemical and structural changes during activation as well as the influence of the initial film composition on the properties of the activated film. Our results demonstrate that the activation process proceeds in parallel with the progressive leaching of phosphorous and formation of cobalt hydroxide as indicated by X-ray photoelectron spectroscopy (XPS).…”

Section: Introductionmentioning

confidence: 99%

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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: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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“…19 Di Palma et al have recently reported ALD deposited cobalt phosphate lms which were used for OER. 20 A number of ALD processes for iron phosphate have been developed by different authors, mostly with the goal of using the material as a lithium-ion battery electrode. [21][22][23] Some of the authors have developed a plasma-enhanced (PE-ALD) method which has the advantage of having much higher growth per cycle (GPC) values than other processes, speeding up deposition times for thicker lms.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…13 Recently, we have demonstrated the synthesis of CoPi by ALD and showed that the developed electrocatalyst is active toward OER and outperforms traditional electrodeposited films. 14 Moreover, the process developed enabled tuning of the Co-to-P ratio by combining the CoPi process with extra ALD cycles of CoO x . The latter approach has led to the improvement of the performance of the electrocatalyst.…”

Section: Introductionmentioning

confidence: 99%

“…The latter approach has led to the improvement of the performance of the electrocatalyst. 14 After electrocatalysis, it is expected that CoPi, as well as other transition metal phosphates prepared by ALD, 15,16 can also have interesting applications in thin film lithium ion batteries. For example, LiCoPO 4 has already been reported [17][18][19] for that application.…”

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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Atomic layer deposition of cobalt phosphate thin films for the oxygen evolution reaction

Cited by 25 publications

References 34 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

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

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

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