Professor Dr Joachim Heitbaum

Wohlfahrt‐Mehrens, M.

doi:10.1007/s10800-006-9189-9

Cited by 28 publications

(35 citation statements)

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“…Subsequent catalysis in H 2 16 O water showed no initial burst of labelled O 2 , but instead a slow release of the 18 O-lable into the product; over a period of 12 hours of continuous O 2 production 22% of the 18 O contained in the oxide appeared in the product. 56,[84][85][86] In accordance with the original interpretation by Nocera and coauthors (see ref 3 for an alternative interpretation), we take this to show that the participation of oxo-bridges in O-O bond formation is a minor side reaction that reflects either a low probability for intramolecular coupling between terminal ligands and μ-oxo bridges or structural changes of the amorphous CoP i -oxides during catalysis. 56 Similarly, Frei and coworkers found neither an initial burst of 16 57 This is likely due to the lower sensitivity of the mass spec technique employed, which made it necessary to accumulate the O 2 produced during 10 min of photocatalysis before the isotopologue ratios could be determined.…”

Section: A Slowly Exchangeable Water Pool or Different Reactivity Of supporting

confidence: 86%

First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

Koroidov

Anderlund

Styring

et al. 2015

Energy Environ. Sci.

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ARTICLE This journal isCo-oxides are promising water oxidation catalysts for artificial photosynthesis devices. Presently, several different proposals exist for how they catalyze O 2 formation from water. Knowledge about this process at molecular detail will be required for their further improvement. Here we present time-resolved 18 O-labelling isotope-ratio membrane-inlet mass spectrometry (MIMS) experiments to study the mechanism of water oxidation in Co/methylenediphosphonate (Co/M2P) oxide nanoparticles using [Ru(bpy) 3 ] 3+ (bpy = 2,2'bipyridine) as chemical oxidant. We show that 16 O-Co/M2P-oxide nanoparticles produce 16 O 2 during their first turnover after simultaneous addition of H 2 18 O and [Ru(bpy) 3 ] 3+ , while sequential addition with a delay of 3 s yields oxygen reflecting bulk water 18 O-enrichment. This result is interpreted to show that the O-O bond formation in Co/M2P-oxide nanoparticles occurs via intramolecular oxygen coupling between two terminal Co-OH n ligands that are readily exchangeable with bulk water in the resting state of the catalyst. Importantly, our data allow the determination of the number of catalytic sites within this amorphous nanoparti cular material, to calculate the TOF per catalytic site and to derive the number of holes needed for the production of the first O 2 molecule per catalytic site. We propose that the mechanism of O-O bond formation during bulk catalysis in amorphous Co-oxides may differ from that taking place at the surface of crystalline materials.

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Section: A Slowly Exchangeable Water Pool or Different Reactivity Of supporting

confidence: 86%

First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

Koroidov

Anderlund

Styring

et al. 2015

Energy Environ. Sci.

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“…This concept is based on two different routes for the origin of oxygen formation whilst water splitting. The so called "oxide route" is used for materials that releases oxygen out of the metal-oxide containing surface 64,65 whereas for a different group of materials adsorbed water molecules represent the oxygen source responsible for the OER (solution route) 66 .…”

Section: Oer Properties Of Surface Modified Special Alloy Ni42mentioning

confidence: 99%

Steel-based electrocatalysts for efficient and durable oxygen evolution in acidic media

Schäfer

Küpper

Schmidt

et al. 2018

Catal. Sci. Technol.

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2High overpotentials, particularly an issue of common anode materials, hamper the process of water electrolysis for clean energy generation. Thanks to immense research efforts up to date oxygen evolution electrocatalysts based on earth-abundant elements work efficiently and stably in neutral and alkaline regimes. However, non-noble metal-based anode materials that can withstand low pH regimes are considered to be an indispensable prerequisite for the water splitting to succeed in the future.All oxygen evolving electrodes working durably and actively in acids contain Ir at least as an additive. Due to its scarcity and high acquisition costs noble elements like Pt, Ru and Ir need to be replaced by earth abundant elements. We have evaluated a Ni containing stainless steel for use as an oxygen-forming electrode in diluted H 2 SO 4 . Unmodified Ni42 steel showed a significant weight loss after long term OER polarization experiments. Moreover, a substantial loss of the OER performance of the untreated steel specimen seen in linear sweep voltammetry measurements turned out to be a serious issue. However, upon anodization in LiOH, Ni42 alloy was rendered in OER electrocatalysts that exhibit under optimized synthesis conditions stable overpotentials down to 445 mV for 10 mA cm -2 current density at pH 0. Even more important: The resulting material has proven to be robust upon long-term usage (weight loss: 20 µg/mm 2 after 50 ks of chronopotentiometry at pH 1) towards OER in H 2 SO 4 . Our results suggest that electrochemical oxidation of Ni42 steel in LiOH (sample Ni42Li205) results in the formation of a metal oxide containing outer zone that supports solution route-based oxygen evolution in acidic regime accompanied by a good stability of the catalyst.3

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“…Meanwhile, both of RuO 2 and IrO 2 are considered as the most suitable OER catalysts, but they are limited by high price, scarce sources, and low stability. In addition, RuO 2 and IrO 2 are easily oxidized into soluble RuO 4 and IrO 3 under high anodic potential, respectively ,. Therefore, highly effective catalytic materials with abundant reserves, such as metal carbide, oxides, sulfides, hydroxide and so on, have been studied for ORR and OER.…”

Section: Introductionmentioning

confidence: 99%

Mn₃O₄@C Nanoparticles Supported on Porous Carbon as Bifunctional Oxygen Electrodes and their Electrocatalytic Mechanism

Cao

et al. 2018

ChemElectroChem

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Mn3O4 nanoparticles encapsulated inside carbon nanospheres supported on a carbon plate (Mn3O4@CS/CP) were designed, their bifunctional electrocatalytic performance for both, the oxygen evolution reaction (OER) at the anode and the oxygen reduction reaction (ORR) at the cathode were studied in alkaline solution. The prepared Mn3O4@CS/CP catalyst exhibits excellent electrocatalytic performance towards ORR, with less negative onset potential and long durability. Combining the results of in‐situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations, it is revealed that Mn3O4 acts as active site for ORR to promote the transformation of OH* into OH−. In addition, Mn3O4@CS/CP possesses an excellent electrochemical OER performances with the lower overpotential along with prosper Tafel slope and robust durability. DFT calculations show the transformation from O* to OOH* is the rate determining step for OER, and Mn3O4@CS/CP shows the minimum barrier, indicating that graphene sheet on the outer of Mn3O4 improves the transformation from O* to OOH*. The oxygen electrode activity parameter (potential difference between OER at current density of 10 mA/cm2 and ORR at current density of −2 mA/cm2) on Mn3O4@CS/CP is 0.72 V, which is superior to those of most bifunctional electrocatalysts reported to date, predicting a promising application in metal‐air batteries and fuel cells.

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Professor Dr Joachim Heitbaum

Cited by 28 publications

References 0 publications

First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

Steel-based electrocatalysts for efficient and durable oxygen evolution in acidic media

Mn₃O₄@C Nanoparticles Supported on Porous Carbon as Bifunctional Oxygen Electrodes and their Electrocatalytic Mechanism

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Professor Dr Joachim Heitbaum

Cited by 28 publications

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First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles

Steel-based electrocatalysts for efficient and durable oxygen evolution in acidic media

Mn3O4@C Nanoparticles Supported on Porous Carbon as Bifunctional Oxygen Electrodes and their Electrocatalytic Mechanism

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Mn₃O₄@C Nanoparticles Supported on Porous Carbon as Bifunctional Oxygen Electrodes and their Electrocatalytic Mechanism