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March 2018

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CC BY 4.0

Authors:

Sonia Jaskaniec

Trinity College Dublin

Christopher Hobbs

Trinity College Dublin

Universidade NOVA de Lisboa

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Available via license: CC BY 4.0

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Supplementary information

Low-temperature synthesis and investigation into the formation

mechanism of high quality Ni-Fe layered double hydroxides

hexagonal platelets

Sonia Jaśkaniec,a,b Christopher Hobbs,b,c Andrés Seral-Ascaso,b,c João Coelho,a,b

Michelle P. Browne,d Daire Tyndall,a,b Takayoshi Sasakie and Valeria Nicolosia,b,c,*

aSchool of Chemistry, Trinity College Dublin, Ireland

bCRANN&AMBER, Trinity College Dublin, Ireland

cSchool of Physics, Trinity College Dublin, Ireland

dSchool of Chemistry, Queens University Belfast, Ireland

eNational Institute for Materials Science, Tsukuba, Japan

*nicolov@tcd.ie

Fig. S1 Cyclic voltammetry of Ni foam in 1 M KOH

Fig. S2 UV-Vis spectra of Ni(NO3)2 and Fe(NO3)3 dissolved in water.

Fig. S3 Absorbance at 350 nm at different stirring time at room temperature.

Fig. S4 SEM micrographs of NixFey LDH formed after a) 4 hours, b) 12 hours and c) 24 hours of

heating.

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Low-temperature synthesis of high quality Ni-Fe layered double hydroxides hexagonal platelets

Article

March 2018

Sonia Jaskaniec · Christopher Hobbs · Andres Seral-Ascaso · Joao Coelho · Valeria Nicolosi

Article

Full-text available

Low-temperature synthesis of high quality Ni-Fe layered double hydroxides hexagonal platelets

March 2018 · Scientific Reports

This paper describes the wet-chemistry synthesis of highly crystalline hexagonal flakes of Ni-Fe layered double hydroxide (LDH) produced at temperature as low as 100 oC. The flakes with diameter in the range of 0.5-1.5 um and the thickness between 15 and 20 nm were obtained by homogeneous precipitation method with the use of triethanolamine (TEA) and urea. By analyzing the intermediate products, ... [Show full abstract] it is suggested that, differently from previous reports, a thermodynamically metastable iron oxyhydroxide and Ni-TEA complex are firstly formed at room temperature. Subsequently, when the mixture is heated to 100 oC and the pH increases due to the thermal decomposition of urea, Ni2+ and Fe3+ are slowly released and then recombine, thus leading to formation of pure, highly-crystalline Ni-Fe LDH flakes. This material showed promising results as an electrocatalyst in oxygen evolution reaction (OER) providing an overpotential value of 0.36 V.

Preprint

Low-temperature synthesis of high quality Ni-Fe layered double hydroxides hexagonal platelets

September 2017

This paper describes the wet-chemistry synthesis of highly crystalline hexagonal flakes of Ni-Fe layered double hydroxide (LDH) produced at temperature as low as 100 oC. The flakes with diameter in the range of 0.5-1.5 um and the thickness between 15 and 20 nm were obtained by homogeneous precipitation method with the use of triethanolamine (TEA) and urea. By analyzing the intermediate products, ... [Show full abstract] it is suggested that, differently from previous reports, a thermodynamically metastable iron oxyhydroxide and Ni-TEA complex are firstly formed at room temperature. Subsequently, when the mixture is heated to 100 oC and the pH increases due to the thermal decomposition of urea, Ni2+ and Fe3+ are slowly released and then recombine, thus leading to formation of pure, highly-crystalline Ni-Fe LDH flakes. This material showed promising results as an electrocatalyst in oxygen evolution reaction (OER) providing an overpotential value of 0.36 V.

Article

Tailored Nickel-Iron Layered Double Hydroxide Particle Size for Optimized O.E.R. Catalysis

July 2018 · ECS Meeting Abstracts

The oxygen evolution reaction (OER) has drawn significant interest in the field of renewable and sustainable energy in recent years, with potential applications for hybrid electric vehicles (HEV) in the form of hydrogen fuel cells and metal-air batteries, among others. Perhaps the most significant feature of OER is the fact that it is a necessary ‘step’ in the evolution of H 2 gas by water ... [Show full abstract] electrolysis, bringing with it an associated potential (E ≈ 1.23 V). To overcome this potential barrier with minimum overpoetential (η), an effective electrocatalyst is required to facilitate the reaction. Nickel-Iron Layered Double Hydroxide (NiFe-LDH) has been shown to exhibit efficient catalysis of the OER, demonstrating overpotentials in composite systems which are competitive with previously studied electrocatalysts based on rare earth metals such as ruthenium and iridium [1] , as well as being competitive in an economic perspective. NiFe-LDH has other advantages over rare earth catalysts such as earth abundance, cost and stability (in operating conditions). The nature of the material in question is that the catalytic active sites are located at the edges of NiFe-LDH hexagonal crystals. This means that particle size will play an important role in its catalytic ability. Synthesis of high quality, planar NiFe-LDH platelets with regular hexagonal morphology was achieved using a wet chemistry method at a relatively low temperature (100 o C) using triethanolamine (TEA) as a ‘capping agent’ to allow homogeneous coprecipitation of both the nickel and iron metal centers within brucite-like layers. Using platelets synthesized in this way, OER catalysis has been demonstrated with η = 0.36 V, a competitive value when compared to many state-of-the-art OER electrocatalysts in the same conditions [3] (5 mVs ⁻¹ , quoted at current density j = 10 mAcm ⁻² ). The work aims to develop methods of post-synthetic treatment of NiFe-LDH dispersions to reduce lateral platelet dimensions and further improve edge-site density for electrocatalytic optimization. This study comes in accordance with the growing number of high-performance electrocatalysts being studied for OER [4] . Size studies have revealed lateral dimensions between 0.4 – 1 µm for the as-produced NiFe-LDH platelets with mean lateral size 0.74 µm (± 0.2). Using only centrifugation as a separation technique, in the range 500 to 3000 rotations per minute (rpm), it was possible to isolate platelet dispersions with mean lateral size down to 0.4 µm (± 0.2) (see figure). While an improvement in overpotential was observed for this method, a much more effective and economical method of size reduction can be achieved by using high-frequency tip-sonication to mechanically ‘break’ the LDH platelets in order to expose a higher density of active edge sites. The goal of this work is to understand the extent to which this technique can be used for the benefit of OER catalysis. To do this we essentially need to understand how small can we efficiently isolate ‘broken’ particle dispersions without compromising the NiFe-LDH’s intrinsic catalytic ability or compatibility with previously successful composite materials. [1] Gong M.; Li Y.; Wang H.; Liang Y.; Wu J. Z.; Zhou J.; Wang J.; Regier T.; Wei F.; Dai H. Journal of the American Chemical Society 2013 135 (23), 8452-8455. [2] Song F.; X. Hu, Nat. Comm , 2014 Volume 5, 447. [3] Tahir M.; Pan L.; Idrees F.; Zhang X.; Wang L.; Zou J.; Lin Wang Z. Nano Energy , Volume 37, 2017 , Pages 136-157. [4] Eftekhari A. Materials Energy Today , Volume 5, 2017 , Pages 37-57. Figure 1

Preprint

Full-text available

The Potential of MXene Materials as a Component in the Catalyst Layer for the Oxygen Evolution React...

December 2022

MXenes are a class of 2D/layered materials which are highly conductive, hydrophilic, have a large electrochemical surface area and are easily processible into electrodes for energy applications. Since the discovery of MXenes over ten years ago, these materials have been mainly used in the preparation of electrodes for batteries and supercapacitors. However, due to their aforementioned properties, ... [Show full abstract] MXenes could potentially be utilised as a component in the catalyst layer for the Oxygen Evolution Reaction (OER). This opinion piece will discuss some of the recent literature in the area of hybrid catalysts consisting of various Transition Metal Oxides (TMOs) and MXenes for the OER. We will also discuss current drawbacks and future outlook in this new area of research.