Recent Developments on Cr‐Based Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Media

Babu, Sreejith P.; Falch, Anzel

doi:10.1002/cctc.202200364

Cited by 12 publications

(8 citation statements)

References 134 publications

(296 reference statements)

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“…The precise role of Fe is still in discussion, and it could either act as an active site for the reaction or activate it. , Co alloyed with Ni yields a bifunctional material able to electrocatalyze both alkaline HER and OER. Concerning Cr, its presence enables the catalytic alloy to be effectively protected against corrosion. , These catalytic materials are usually deposited on conducting (metal foam or carbon) substrates by either electrochemical or hydrothermal methods from the corresponding metal salts. , Although these simple and fast methods allow the catalyst structure to be controlled at the nanometer scale, their industrial scale-up is, however, not so easy.…”

Section: Introductionmentioning

confidence: 99%

Efficient and Highly Stable 3D-Printed NiFe and NiCo Bifunctional Electrodes for Practical HER and OER

Tourneur,

Joanny,

Perrin

et al. 2023

ACS Appl. Eng. Mater.

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Considered like a fully renewable and clean energy carrier with the highest energy density, dihydrogen (H 2 ) constitutes the best alternative to fossil fuels for ensuring the sustainability of energy. This technologically and industrially relevant energy vector can be produced by water electrolysis that is now widely recognized as an eco-friendly, scalable, and carbonfree route. In that context, alkaline water electrolysis is an affordable technology because it allows the use of transition metals as electrocatalysts for both hydrogen (HER) and oxygen (OER) evolution reactions. Here, combining catalytically active transition metal alloys (NiFe and NiCo) with a 3D printing technique, namely, selective laser melting (SLM), enables access to ca. 25 cm 2 microstructured cylindrical electrodes, efficiently promoting alkaline HER and OER. NiCo is found to be the most efficient electrode for HER, with an overpotential of 210 mV at 10 mA cm −2 . It is also the most stable electrode when studied in operation during prolonged electrolysis, with a potential change of only 40 mV after 140 h of electrolysis at 50 mA cm −2 (1.25 A). Regarding the OER, NiFe shows the highest catalytic activity with an overpotential of 300 mV at 10 mA cm −2 and the greatest stability in operation with an electrolysis-induced potential change of only 30 mV. Further surface characterization techniques (scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), contact angle measurements, and analysis of electrogenerated gas bubbles) are used to monitor the electrolysis-induced chemical changes and to get valuable information on the bubble dynamics. Interestingly, electrolysis is found to be beneficial for enhancing the hydrophilicity and/or the aerophobicity of the electrodes, thus facilitating the detachment of the H 2 or O 2 bubbles.

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Section: Introductionmentioning

confidence: 99%

Efficient and Highly Stable 3D-Printed NiFe and NiCo Bifunctional Electrodes for Practical HER and OER

Tourneur,

Joanny,

Perrin

et al. 2023

ACS Appl. Eng. Mater.

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“…[ 62,63 ] This is consistent with observations that Cr–based OER catalysts show high activity upon conversion to Cr 6+ in the interplay with graphene. [ 64–66 ] The fact that the occurrence of Cr 6+ increases the OER activity is supported by the observation of increasing activity with increasing OER cycle repetitions (Figure 5i). This rapid activation was not observed in bulk Cr 2 O 3 .…”

Section: Resultsmentioning

confidence: 66%

Angstrom‐Confined Electrochemical Synthesis of Sub‐Unit‐Cell Non‐Van Der Waals 2D Metal Oxides

Lee

Nishina

et al. 2023

Advanced Materials

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Bottom‐up electrochemical synthesis of atomically thin materials is desirable yet challenging, especially for non‐van der Waals (non‐vdW) materials. Thicknesses below a few nanometers have not been reported yet, posing the question how thin can non‐vdW materials be electrochemically synthesized. This is important as materials with (sub‐)unit‐cell thickness often show remarkably different properties compared to their bulk form or thin films of several nanometers thickness. Here, a straightforward electrochemical method utilizing the angstrom‐confinement of laminar reduced graphene oxide (rGO) nanochannels is introduced to obtain a centimeter‐scale network of atomically thin (<4.3 Å) 2D‐transition metal oxides (2D‐TMO). The angstrom‐confinement provides a thickness limitation, forcing sub‐unit‐cell growth of 2D‐TMO with oxygen and metal vacancies. It is showcased that Cr2O3, a material without significant catalytic activity for the oxygen evolution reaction (OER) in bulk form, can be activated as a high‐performing catalyst if synthesized in the 2D sub‐unit‐cell form. This method displays the high activity of sub‐unit‐cell form while retaining the stability of bulk form, promising to yield unexplored fundamental science and applications. It is shown that while retaining the advantages of bottom‐up electrochemical synthesis, like simplicity, high yield, and mild conditions, the thickness of TMO can be limited to sub‐unit‐cell dimensions.

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“…[62,63] This is consistent with observations that Cr based OER catalyst show high activity upon conversion to Cr 6+ in the interplay with graphene. [64][65][66] The fact that the occurrence of Cr 6+ increases the OER activity is supported by the observation of increasing activity with increasing OER cycle repetitions (Figure 5i). And this rapid activation was not observed in bulk Cr2O3.…”

Section: Catalytic Activationmentioning

confidence: 60%

Angstrom-confined electrochemical synthesis of sub-unit cell non van der Waals 2D metal oxides

Lee

Nishina

et al. 2023

Preprint

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Bottom-up electrochemical synthesis of atomically thin materials is desirable yet challenging, especially for non-van der Waals (vdW) materials. Thicknesses below few nm have not been reported yet, posing the question how thin can non-vdW materials be electrochemically synthesized? This is important as materials with (sub-) unit cell thickness often show remarkably different properties compared to their bulk form or thin films of several nm thickness. Here, we introduce a straightforward electrochemical method utilizing the angstrom-confinement of laminar reduced graphene oxide (rGO) nanochannels to obtain a centimeter-scale network of atomically thin (< 0.43nm) 2D-transition metal oxides (2D-TMO). The angstrom-confinement provides a thickness limitation, forcing sub-unit cell growth of 2D-TMO with oxygen and metal vacancies. We showcase that Cr2O3, a material without significant catalytic activity for OER in bulk form, can be activated as a high-performing catalyst if synthesized in the 2D sub-unit cell form. Our method displays the high activity of sub-unit cell form while retaining the stability of bulk form, promising to yield unexplored fundamental science and applications. We show that while retaining the advantages of bottom-up electrochemical synthesis like simplicity, high yield, and mild conditions, the thickness of TMO can be limited to sub-unit cell dimensions.

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Recent Developments on Cr‐Based Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Media

Cited by 12 publications

References 134 publications

Efficient and Highly Stable 3D-Printed NiFe and NiCo Bifunctional Electrodes for Practical HER and OER

Efficient and Highly Stable 3D-Printed NiFe and NiCo Bifunctional Electrodes for Practical HER and OER

Angstrom‐Confined Electrochemical Synthesis of Sub‐Unit‐Cell Non‐Van Der Waals 2D Metal Oxides

Angstrom-confined electrochemical synthesis of sub-unit cell non van der Waals 2D metal oxides

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