Efficient direct seawater electrolysers using selective alkaline NiFe-LDH as OER catalyst in asymmetric electrolyte feeds

Dresp, Sören; Thanh, Trung Ngo; Klingenhof, Malte; Brückner, Sven; Hauke, Philipp; Strasser, Peter

doi:10.1039/d0ee01125h

Cited by 283 publications

(220 citation statements)

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“…The hydrogen and oxygen produced from seawater splitting have tremendous advantages over freshwater, due to the huge storage of salty water on earth [10]. However, practical seawater electrolysis still faces various challenges to overcome, such as unsatisfactory oxygen evolution reaction (OER) kinetics and impairment of chlorine electrochemistry [11][12][13]. Compared to two-electron involved hydrogen evolution reaction (HER), four-electron participated OER is such a sluggish process that considered as a bottleneck of water electrolysis [14,15].…”

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confidence: 99%

Heterogeneous lamellar-edged Fe-Ni(OH)2/Ni3S2 nanoarray for efficient and stable seawater oxidation

et al. 2020

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Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction (OER) and the impairment of chlorine electrochemistry at anode. Herein, we report a heterostructure of Ni 3 S 2 nanoarray with secondary Fe-Ni(OH) 2 lamellar edges that exposes abundant active sites towards seawater oxidation. The resultant Fe-Ni(OH) 2 /Ni 3 S 2 nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater. It only requires an overpotential of 269 mV to afford a current density of 10 mA•cm −2 and the Tafel slope is as low as 46 mV•dec −1. The 27-hour chronopotentiometry operated at high current density of 100 mA•cm −2 shows negligible deterioration, suggesting good stability of the Fe-Ni(OH) 2 /Ni 3 S 2 @NF electrode. Faraday efficiency for oxygen evolution is up to ~ 95%, revealing decent selectivity of the catalyst in saline water. Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites. The density functional theory (DFT) calculations indicate that the OER has lower theoretical overpotential than Cl 2 evolution reaction in Fe sites, which is contrary to that of Ni sites. The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.

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confidence: 99%

Heterogeneous lamellar-edged Fe-Ni(OH)2/Ni3S2 nanoarray for efficient and stable seawater oxidation

et al. 2020

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“…Indeed, so far, all reports rely on the aforementioned qualitative arguments or assume large cell voltages of 4.5 V for DSS in contrast to currently reported seawater electrolysers, and no investigation exists that compares the costs for the purification of seawater with those of splitting it. 17,22,30 Herein, we answer the question: Can DSS (see Fig. 1 left) be competitive to a two-step scenario where seawater is first purified and subsequently split (see Fig.…”

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“…1,10,16,17 At a first glance, these arguments seem convincing and have led to substantial interest in DSS with several elaborate publications in high quality journals. 10,11,[24][25][26][27][28][29]14,15,[18][19][20][21][22][23] However, as pointed out in a recent review article on DSS published in the journal Nature Energy, 11 "a comprehensive review with up-to-date costs is still needed." Indeed, so far, all reports rely on the aforementioned qualitative arguments or assume large cell voltages of 4.5 V for DSS in contrast to currently reported seawater electrolysers, and no investigation exists that compares the costs for the purification of seawater with those of splitting it.…”

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Is direct seawater splitting economically meaningful?

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et al. 2021

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“…[6,11] Therefore, it is worthwhile to assess the suitability of using seawater with minimal processing as the electrolyte in alkaline electrolyzer because it is an abundant hydrogen source. [12][13][14][15][16] Furthermore, seawater electrolysis matches well with the marine offshore renewable farms for on-site green hydrogen production. [17] However, the conventional noble metal benchmarks for hydrogen evolution reaction (HER) are unstable in seawater/alkaline seawater electrolysis and cannot be used.…”

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Stable and Highly Efficient Hydrogen Evolution from Seawater Enabled by an Unsaturated Nickel Surface Nitride

et al. 2021

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This is because chlorine evolution takes place at the counter electrode and highly corrosive hypochlorite by-products block the active sites of the noble metal catalysts. [6,13,18] Consequently, development of stable and active electrocatalysts for seawater splitting is of crucial importance for this process. Transition metal nitrides (TMNs) have excellent electrical conductivity and corrosion resistance and have demonstrated good stability for seawater splitting. [18-20] However, most of the bulk TMNs reported exhibit unsatisfactory HER activity due to a suboptimal hydrogen bonding energy. [21,22] Consequently, material optimization strategies, such as vacancy engineering, alloying, interface engineering, and heteroatom doping are usually needed to improve their activity. [23-28] For example, interfacing MoN with C 3 N 4 can greatly promote HER activity in alkaline media. [29] Tungsten and phosphorus doping in Co 3 N can manipulate the dehydrogenation kinetics and increase hydrogen production. [27] Despite significant investigation into TMNs, adequate activity and corrosion resistance are still required to be achieved simultaneously, and more advanced modification methods need to be developed. Manipulating the stoichiometry is one such way to optimize the properties of TMNs. Using this strategy, the N atom ratio in the metal matrix can be tuned to regulate the TMN electronic structure. [18,24,25,30] The two main approaches to controlling the nitrogen content in TMNs are the nitrogen-rich process and the incomplete nitridation process. [31-33] The nitrogen-rich process aims to embed extra nitrogen atoms into the TMN lattice but usually requires high-temperature and high-pressure conditions due to sluggish thermodynamics. [30,31,34,35] The incomplete nitridation process can limit the metal-nitrogen bonding in the matrix and promote the formation of metal/ metal nitride interfaces, which generally offers better conductivity and subsequent electrocatalytic activity. [23,25,33,36] However, the stoichiometry in a metal/metal nitride heterostructure is difficult to control and deficient or superfluous nitridation can lead to poor electrocatalytic activity. Herein, we synthesized a nickel surface nitride encapsulated in a carbon shell (Ni-SN@C) using an unsaturated nitriding process. Compared to conventional TMNs or metal/metal nitride heterostructures, the unsaturated Ni-SN@C has no detectable bulk nickel nitride phase. Instead, the main chemical composition of Ni-SN@C is metallic Ni but with unique Electrocatalytic production of hydrogen from seawater provides a route to low-cost and clean energy conversion. However, the hydrogen evolution reaction (HER) using seawater is greatly hindered by the lack of active and stable catalysts. Herein, an unsaturated nickel surface nitride (Ni-SN@C) catalyst that is active and stable for the HER in alkaline seawater is prepared. It achieves a low overpotential of 23 mV at a current density of 10 mA cm −2 in alkaline seawater electrolyte, which is superior to Pt/C. Compared to conv...

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Efficient direct seawater electrolysers using selective alkaline NiFe-LDH as OER catalyst in asymmetric electrolyte feeds

Abstract: Increasing the performance of seawater electrolyser and enabling direct natural seawater feed by asymmetric electrolyte flow scheme.

Cited by 283 publications

References 15 publications

Heterogeneous lamellar-edged Fe-Ni(OH)2/Ni3S2 nanoarray for efficient and stable seawater oxidation

Heterogeneous lamellar-edged Fe-Ni(OH)2/Ni3S2 nanoarray for efficient and stable seawater oxidation

Is direct seawater splitting economically meaningful?

Stable and Highly Efficient Hydrogen Evolution from Seawater Enabled by an Unsaturated Nickel Surface Nitride

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