Oxidized Mild Steel S235: An Efficient Anode for Electrocatalytically Initiated Water Splitting

Schäfer, Helmut; Küpper, Karsten; Wollschläger, J.; Kashaev, Nikolai; Hardege, Jörg D.; Walder, Lorenz; Beladi‐Mousavi, Seyyed Mohsen; Hartmann‐Azanza, Brigitte; Steinhart, Martin; Sadaf, Shamaila; Dorn, Falk

doi:10.1002/cssc.201500666

Cited by 52 publications

(67 citation statements)

References 77 publications

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“…This impressively confirms the increase of OER performance of Ni42 steel at pH 7 upon this type of surface oxidation. To date the highest electrocatalytic activity for OER on steel surfaces under neutral conditions was reported for surface activated mild steel S235 exhibiting η= 462 mV at 1 mA/cm 2 in pH 7 buffered solution [33] . In general most of the established OER electrocatalysts show at similar overpotentials of around 500 mV a OER current density that is approximately four times lower (1 mA/cm 2 ) [31,30,34,35,36,37] .…”

Section: Resultsmentioning

confidence: 99%

“…We suggested manganese-and iron-oxide species as the potential catalytic active species on the periphery of the chlorinated steel [33] . Electrodeposited FeO(OH) [34,35] besides cobalt-phosphate compounds [36,37] are among the known non noble compounds for which slightly better OER activity (down to 410 mV overpotential at 1 mA/cm 2 ) and acceptable stability during water splitting at neutral pH has been demonstrated [37] .…”

Section: Introductionmentioning

confidence: 94%

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Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

Schäfer

Chevrier

Zhang

et al. 2016

Adv Funct Materials

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Janus type Water-Splitting Catalysts have attracted highest attention as a tool of choice for solar to fuel conversion. AISI Ni 42 steel was upon harsh anodization converted in a bifunctional electrocatalyst. Oxygen evolution reaction-(OER) and hydrogen evolution reaction (HER) are highly efficiently and steadfast catalyzed at pH 7, 13, 14, 14.6 (OER) respectively at pH 0, 1, 13, 14, 14.6 (HER). The current density taken from long-term OER measurements in pH 7 buffer solution upon the electro activated steel at 491 mV overpotential (η) was around 4 times higher (4 mA/cm 2 ) in comparison with recently developed OER electrocatalysts. The very strong voltagecurrent behavior of the catalyst shown in OER polarization experiments at both pH 7 and at pH 13 were even superior to those known for IrO 2 -RuO 2 . No degradation of the catalyst was detected even when conditions close to standard industrial operations were applied to the catalyst. A stable Ni-, Fe-oxide based passivating layer sufficiently protected the bare metal for further oxidation. Quantitative charge to oxygen-(OER) and charge to hydrogen (HER) conversion was confirmed. High resolution XPS spectra showed that most likely γ−NiO(OH) and FeO(OH) are the catalytic active OER and NiO is the catalytic active HER species.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

Schäfer

Chevrier

Zhang

et al. 2016

Adv Funct Materials

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“…As expected, a similar outcome can be derived from the corresponding Tafel lines of samples Co-300 and Ir/Ru, showing a horizontal shift of around 220 mV (Figure 3b). This represents enormous progress, taking into consideration that our group had significant problems with substantially improving the OER properties of steel upon surface oxidation to a level that makes it competitive to IrO 2 -RuO 2 regarding water-splitting properties under neutral conditions 25,45 . Interestingly, at current densities < 5mA/cm 2 the Tafel line belonging to sample Co-300 was substantially stiffer (slope 140.8 mV dec -1 ) than the one assigned to IrO 2 -RuO 2 (slope 225.8 mV dec -1 ) (Figure 3b).…”

Section: Oer Properties In Neutral Mediummentioning

confidence: 99%

“…Unfortunately we could not extract a meaningful FTIR spectrum from the oxide containing surface of Co-300 upon direct measurement of the specimen. This experience we had already put before when surface oxidized steel S235 or AISI 304 were studied 25,26,45 . As the evanescent wave penetrates only up to some microns into the sample a good contact between ATR diamond and the sample is crucial and obviously was not ensured.…”

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confidence: 99%

X20CoCrWMo10-9//Co₃O₄: a metal–ceramic composite with unique efficiency values for water-splitting in the neutral regime

Schäfer

Chevrier

Kuepper

et al. 2016

Energy Environ. Sci.

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In spite of the drastic oil price collapse in the second half of 2014 resulting in a price below 30 $/barrel in January 2016 1 , the exploration of promising renewable energy sources for the Abstract: Water splitting allows the storage of solar energy into chemical bonds (H 2 +O 2 ) and will help to implement the urgently needed replacement of limited available fossil fuels. Particularly in neutral environment electrochemically initiated water splitting suffers from low efficiency due to high overpotentials (η) caused by the anode. Electro-activation of X20CoCrWMo10-9, a Co-based tool steel resulted in a new composite material (X20CoCrWMo10-9//Co 3 O 4 ) that catalyzes the anode half-cell reaction of water electrolysis with a so far-, unequalled effectiveness. The current density achieved with this new anode in pH 7 corrected 0.1 M phosphate buffer is over a wide range of η around 10 times higher compared to recently developed, up-to-date electrocatalysts and represents the benchmark performance advanced catalysts show in regimes that support water splitting significantly better than pH 7 medium. X20CoCrWMo10-9//Co 3 O 4 exhibited electrocatalyticproperties not only at pH 7, but also at pH 13, which is much superior to the ones of IrO 2 -RuO 2 , single-phase Co 3 O 4 -or Fe/Ni-based catalysts. Both XPS and FT-IR experiments unmasked Co 3 O 4 as the dominating compound on the surface of the X20CoCrWMo10-9//Co 3 O 4 composite. Upon a comprehensive dual beam FIB-SEM (focused ion beam-scanning electron microscopy) study we could show that the new composite does not exhibit a classical substrate-layer structure due to the intrinsic formation of the Co-enriched outer zone. This structural particularity is basically responsible for the outstanding electrocatalytic OER performance.2 future is one of the significant challenges for scientists and engineers concerned with energy issues research. Splitting of water into hydrogen and oxygen by exploiting solar energy transforms water to an inexhaustible and environmental friendly fuel source 2,3,4,5,6,7,8,9 .Electrocatalytically initiated hydrogen-and oxygen formation from water is considered an important realization of this solar to fuel conversion route 10,11,12 but is typically hampered by the high overpotentials oxygen evolution on the anode side goes with 13,14 . This is particularly true when the electrochemical cleavage of more or less untreated water is intended-; hence, when the splitting procedure is carried out at neutral pH value. 17,18,19,20,21,22,23,24 . Scheme 1 gives some idea of the position of current heterogeneous catalysts in terms of their efficiency regarding OER in neutral regime. The significant improvement of the voltage-current behavior can be taken from both-, the non-steady state ( Figure 1a) as well as the steady state polarization (Figure 1b) experiments. Results OER properties in neutral mediumThe CV of sample Co-300 shows along the entire curve substantially stronger current to voltage ratio than the CV of sample Co and reached, at the upper...

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“…Chlorine oxidized stainless steels were also shown to be OER catalysts at alkaline (1.5 mA cm −2 at η = 260 mV) and neutral pH (1 mA cm −2 at η = 462 mV). [ 41,42 ] A regenerating ability to enhance stability is also unknown for iron-based water splitting catalysts.…”

Section: Introductionmentioning

confidence: 99%

Bi‐Functional Iron‐Only Electrodes for Efficient Water Splitting with Enhanced Stability through In Situ Electrochemical Regeneration

Martindale

Reisner

2015

Advanced Energy Materials

152

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are the indirect conversion of solar into chemical energy using a photovoltaic (PV)-electrolyzer [ 9,10 ] system and its direct conversion with a photoelectrochemical (PEC) cell. [11][12][13] The International Energy Agency identifi ed a key obstacle to the widespread implementation of water splitting technologies to be the development of cheap and active materials to catalyze both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which operate under identical and mild conditions with high efficiency and stability. [ 14 ] The most active catalysts of the HER and OER contain precious metals: Pt and RuO 2 /IrO 2 , respectively, [15][16][17][18] but there is no real possibility to scale up these materials for global demand due to their scarcity. A sustainable and global process will require the use of inexpensive, widely abundant and nontoxic materials. Figure S1 (Supporting Information) shows the recent cost of transition metal resources and their relative crustal abundance. Rare, high cost elements are suitable for use in luxury items such as catalytic converters in automobiles. Even medium cost-abundance catalysts such as the much investigated HER catalysts, Ni-Mo alloys, [ 19,20 ] as well as Ni 2 P, [ 21 ] CoP, [ 22 ] and MoS 2 , [23][24][25][26] and the OER catalysts, cobaltphosphate (CoP i ), [ 27 ] nickel-borate (NiB i ), 25 and (mixed) metal oxide-hydroxides [29][30][31][32] can still suffer from scalability issues. For example, cobalt constitutes the largest cost in most Li-ion rechargeable batteries (LiCoO 2 ), which has contributed to significant research into its replacement with iron (LiFePO 4 ) and manganese (LiMnO 2 ) analogs. [ 33 ] Approaches to overcome the use of more expensive metals in catalysis include the use of ultra-low concentrations of the active catalyst embedded in a lower-cost matrix [ 34 ] or in this case the identifi cation of active species which contain only Earth-abundant elements. [ 30 ] Only three transition metals (titanium, manganese, and iron) are truly abundant in Earth's crust (the primary source of metal ores) and within this group, iron is by far the most plentiful. Hence iron is arguably the most attractive element on which to base sustainable catalysts, due to its effectively inexhaustible supply, low toxicity, and negligible environmental impact. Despite this, iron-based catalysts have been relatively underreported and underused, probably due to their notoriety for corrosion.Iron-based electrodes for either the HER or the OER have been reported, [35][36][37][38][39][40] but bi-functionally active iron-only materials in water splitting are unknown. For example, FeP is described as a promising high activity noble-metal-free material Scalable and robust electrocatalysts are required for the implementation of water splitting technologies as a globally applicable means of producing affordable renewable hydrogen. It is demonstrated that iron-only electrode materials prove to be active for catalyzing both proton reduction and water oxidation in alkali...

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Oxidized Mild Steel S235: An Efficient Anode for Electrocatalytically Initiated Water Splitting

Cited by 52 publications

References 77 publications

Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

X20CoCrWMo10-9//Co₃O₄: a metal–ceramic composite with unique efficiency values for water-splitting in the neutral regime

Bi‐Functional Iron‐Only Electrodes for Efficient Water Splitting with Enhanced Stability through In Situ Electrochemical Regeneration

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Oxidized Mild Steel S235: An Efficient Anode for Electrocatalytically Initiated Water Splitting

Cited by 52 publications

References 77 publications

Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

X20CoCrWMo10-9//Co3O4: a metal–ceramic composite with unique efficiency values for water-splitting in the neutral regime

Bi‐Functional Iron‐Only Electrodes for Efficient Water Splitting with Enhanced Stability through In Situ Electrochemical Regeneration

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X20CoCrWMo10-9//Co₃O₄: a metal–ceramic composite with unique efficiency values for water-splitting in the neutral regime