Fluorine‐Doped Tin Oxide/Alumina as Long‐Term Robust Conducting Support for Earth‐Abundant Water Oxidation Electrocatalysts

Garcés‐Pineda, Felipe A.; González‐Cobos, Jesús; Torréns, Mabel; Galán‐Mascarós, José Ramón

doi:10.1002/celc.201900218

Cited by 4 publications

(6 citation statements)

References 50 publications

(113 reference statements)

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“…In the two-electrode experiments, the CoFe Prussian blue catalyst was obtained via dip coating. 62 First the glass/FTO electrodes (geometrical area 1 cm 2 ) were dipped in a 0.01 M hexacyanoferrate (K 3 [Fe(CN) 6 ]) solution and then in a 0.01 M cobalt nitrate (Co(NO 3 ) 2 •6H 2 O) solution, each time for 15 min and with magnetic stirring. After five deposition cycles were performed, the electrodes were dried overnight.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

et al. 2021

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Hydrogen is a most desirable solar energy storage medium. It provides reliable, scalable, and long-term energy storage, while helping in the decarbonization of the energy cycle. Such a storage medium is required for further deployment of photovoltaics, either for their inclusion into transportation and heavy industries or for supporting renewable grid management. The most accessible hydrogen source is water. However, fresh water is a scarce resource, while seawater is abundant worldwide. A major drawback of seawater electrolysis comes from chloride oxidation competing with the oxygen evolution reaction (OER). This may produce toxic products such as chlorine and also limits the hydrogen energy efficiency of the overall process. Thus, selective catalysts toward the OER are of strong technological interest. Here we report the electrocatalytic activity of heterogeneous cobalt hexacyanoferrate toward seawater oxidation. Combining experimental and computational studies, we highlight the great difficulty in obtaining such selectivity and its main mechanistic descriptors. This Prussian blue derivative is an excellent and robust OER electrocatalyst, but unfortunately, it is not selective enough toward the OER in the presence of Cl– anions. Faradaic efficiencies above 30% toward Cl2 were observed during untreated seawater bulk electrolysis.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

et al. 2021

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“…As a plausible oxidation catalyst for organic substrates, we investigated cobalt hexacyanoferrate (CoFePB), a versatile and robust oxidation catalyst in a wide pH range, with a proven performance in water oxidation (photo)electrocatalysis. − In the present work we have found that CoFePB offers excellent selectivity and efficiency toward aqueous HCOO – oxidation under a range of pH 1–13. Its performance was evaluated electrochemically and has been compared with that of state-of-the-art catalysts, also providing mechanistic insights on the reaction kinetics.…”

Section: Introductionmentioning

confidence: 99%

Cobalt Hexacyanoferrate as a Selective and High Current Density Formate Oxidation Electrocatalyst

Han

González‐Cobos

Sánchez‐Molina

et al. 2020

ACS Appl. Energy Mater.

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Herein we report the selectivity, stability, and electrochemical characterization of cobalt hexacyanoferrate, the Co-Fe Prussian Blue derivative (CoFePB), as a formate/formic acid oxidation electrocatalyst in aqueous media. CoFePB is able to quantitatively catalyze (100% Faradaic efficiency within less than 8% standard error at pH 5) the electrochemical oxidation of formate to CO2 over a pH range of 1-13. This quantitative formate elecrooxidation is possible due to the exclusive selectivity of the catalyst in a wide potential window (from c.a. 0.8 to 1.3 V vs. NHE at pH 7), where no other substrate in aqueous conditions is activated: neither other organic molecules, such as alcohols or acids, nor water itself. CoFePB is one of the first heterogeneous noble-metal-free catalysts reported for the electrooxidation of small hydrocarbon molecules. Importantly, the catalyst showed a very high tolerance against surface poisoning during the reaction, as supported by the cyclic voltammetry and electrochemical impedance spectroscopy data, thereby allowing CoFePB to operate at greater current density than state-of-the-art noble metal catalysts. For example, we observed that CoFePB is able to achieve a formate oxidation current ~10 mA cm -2 at pH 5, 0.4 M formate at 1.1 V vs NHE, whereas a Pt disk and Pd(5%)/C electrodes had a current of 0.4 and 1.4 mA cm -2 , respectively, under identical conditions. The remarkable selectivity, stability, and high current density of CoFePB, in contrast to state-of-the-art catalysts based on platinum-group metals (PGM), is an important step in the search for inexpensive earth-abundant materials for oxidation of organic molecules for use in liquid fuel cells or for selective organic molecule sensors. Furthermore, because CoFePB is not poisoned by intermediates and can achieve higher current density than Pt or Pd, improvement of the catalyst onset potential can lead to higher power density formate oxidation fuel cells using earth abundant metals than with Pt or Pd.

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“…Since the relative current profiles are similar between all the substrates, including the bare BiVO 4 electrodes, we assume that the loss of activity during the first 2 h is mainly due to the deactivation of the underlying BiVO 4 . Deactivation of FTO crystallites may also occur, even though this substrate is reported to be robust under the applied experimental conditions . In addition, previous studies, using XPS, inductively coupled plasma, and infrared spectroscopy, reported high long term stability of CoFe Prussian blue catalysts on BiVO 4 and good redox reversibility of the Co and Fe metallic centers after the catalytic process, indicating that drastic changes in the electronic properties of the materials are unlikely.…”

Section: Resultsmentioning

confidence: 89%

“…31 Deactivation of FTO crystallites may also occur, even though this substrate is reported to be robust under the applied experimental conditions. 51 In addition, previous studies, using XPS, inductively coupled plasma, and infrared spectroscopy, reported high long term stability of CoFe Prussian blue catalysts on BiVO 4 31 and good redox reversibility of the Co and Fe metallic centers after the catalytic process, 30 indicating that drastic changes in the electronic properties of the materials are unlikely. Interestingly, we observed large variations of the current transients, which recover their maximum intensity after several hours.…”

Section: Resultsmentioning

confidence: 99%

Ligand Effects of Penta- and Hexacyanidoferrate-Derived Water Oxidation Catalysts on BiVO₄ Photoanodes

Pires

Hegner

Bonacin

et al. 2020

ACS Appl. Energy Mater.

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The design of an efficient, robust, and cost-competitive photoanode is often considered to be the bottleneck step to an industrial implementation of artificial photosynthesis. To overcome its drawbacks and to improve photoelectrochemical performance, water oxidation co-catalysts can be deposited on the photoanode. Coordination polymers based on Prussian blue, that is, cobalt cyanidoferrates, have emerged as promising water oxidation catalysts because of their low cost and tunable composition, while maintaining high efficiency and stability in a wide range of pH. They present an excellent alternative to typically used metal oxides, which show limited efficiency improvement. Indeed, the hexacyanidoferrate analog K x Co y [Fe(CN) 6 ]•nH 2 O appears to be an outstanding co-catalyst for decorating bismuth vanadate (BiVO 4 ) photoanodes, by enabling fast and irreversible hole transfer, combined with high catalytic efficiency. Because intrinsic catalytic activity can be modulated and enhanced by the introduction of pentacyanidoferrate precursors, we compared the effect of different pentacyanidoferrate derivatives on bismuth vanadate photoanodes for light-driven water oxidation. Our results indicate that the coordination polymers prepared using [Fe(CN) 5 (NH 3 )] 3− as a precursor lead to higher photocurrents and lower onset potential shifts. It is suggested that the relation between catalytic activity and ligand substitution is a combination of electronic effects imposed by the nature of the ligand and morphological effects, which regulate the number of active sites exposed and charge transport across the catalyst layer.

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Fluorine‐Doped Tin Oxide/Alumina as Long‐Term Robust Conducting Support for Earth‐Abundant Water Oxidation Electrocatalysts

Cited by 4 publications

References 50 publications

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

Cobalt Hexacyanoferrate as a Selective and High Current Density Formate Oxidation Electrocatalyst

Ligand Effects of Penta- and Hexacyanidoferrate-Derived Water Oxidation Catalysts on BiVO₄ Photoanodes

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Fluorine‐Doped Tin Oxide/Alumina as Long‐Term Robust Conducting Support for Earth‐Abundant Water Oxidation Electrocatalysts

Cited by 4 publications

References 50 publications

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

Understanding the Catalytic Selectivity of Cobalt Hexacyanoferrate toward Oxygen Evolution in Seawater Electrolysis

Cobalt Hexacyanoferrate as a Selective and High Current Density Formate Oxidation Electrocatalyst

Ligand Effects of Penta- and Hexacyanidoferrate-Derived Water Oxidation Catalysts on BiVO4 Photoanodes

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Ligand Effects of Penta- and Hexacyanidoferrate-Derived Water Oxidation Catalysts on BiVO₄ Photoanodes