Chemical transformation approach for high-performance ternary NiFeCo metal compound-based water splitting electrodes
Graphical abstract
Introduction
Electrochemical water splitting provides a promising Environmental-friendly route to the hydrogen (H2) production [[1], [2], [3]]. However, oxygen evolution reaction (OER) catalyst is kinetically limited at the anode of a water electrolyzer. At actual operating current density, the high overpotential required for this reaction reduces the water splitting efficiency [[4], [5], [6]]. Currently, commercial IrO2 and RuO2 catalysts are known as OER catalysts with high activity. However, cost-effective OER catalysts that have lower overpotential than existing precious catalysts are required for the efficient and economical electrochemical water splitting [[7], [8], [9]]. Moreover, the most effective catalysts for the hydrogen evolution reaction (HER) are based on Pt, which is costly and rare [[10], [11], [12], [13]]. To address this issue, various OER and HER catalysts based on non-precious, earth-abundant elements have been explored, including transition metal oxides [14,15], (oxy)hydroxides [[16], [17], [18], [19]], nitrides [20,21], phosphides [[22], [23], [24]], and sulfides [25,26]. Alkaline and Anion exchange membrane (AEM) water electrolyzers are attracting much attention because they can use non-precious metal catalysts. However, despite recent progress, most of water electrolysis reported so far require large overpotentials of ≥ 300 mV to reach current densities of ≥10 mA/cm2 in alkaline water electrolysis, and high current density of ≥500 mA/cm2 to reach ≥1.8 Vcell in AEM water electrolysis [9], and further improvement in OER and HER activities is needed to achieve low-overpotential water splitting.
Chemical transformation often allows to produce nanostructures with an unconventional morphology or composition that cannot be achieved otherwise [[23], [24], [25], [26]]. Corrosion is a chemical transformation reaction that occurs between metals with different reduction potentials facing each other [27,28]. Many studies have been done to prevent undesirable effects of the corrosion which cause damage or failure of metals and metal alloys. Here we demonstrate that corrosion can be harnessed to chemically transform a conventional metal foam into a high-performance OER electrode. Ni foams (NF) were corroded in aqueous solutions with Fe3+ and Co2+ cations to obtain OER electrodes composed of double hydroxide (LDH) nanosheets with a ternary NiFeCo layer supported by NF, which exhibited an OER current density of 10 mA/cm2 at a potential of only 1.4 V (iR corrected). To our knowledge, the presented ternary NiFeCo LDH electrode is one of the most active OER electrodes in alkaline media reported to date [8]. This OER electrode was further converted to an HER electrode consisting of a ternary NiFeCo phosphide nanosheet array via a subsequent phosphidation process, which showed an HER activity as high as a commercial Pt/C catalyst. These two electrodes were coupled to construct an alkaline water electrolyzer that achieved a current density of 10 mA/cm2 at only 1.47 Vcell (iR corrected), which was 160 mV better than the IrO2 and Pt/C catalyst pairs. We also used these electrodes to fabricate an AEM water electrolyzer that reached a cell current density of 500 mA/cm2 at only 1.75Vcell (without iR-corrected). Our electrodes showed excellent catalytic stability without compromising performance in both alkaline and AEM electrolyzers. Our synthesis method does not require the dispersion or coating technology of additional catalysts. Furthermore, this chemical transformation method is readily scalable, providing a promising route for large-area production of high-efficiency and low-cost OER and HER electrodes for efficient electrochemical water splitting.
Section snippets
Corrosion of NF
The oxide layer on the NF surface was removed by reducing heat treatment in a H2/Ar atmosphere for 2 h at 800 °C in a tube furnace. The NF was immersed in an aqueous solution in which Co(CH3COO)2 (33.3 mM) and Fe(NO3)3·9H2O (66.7 mM) were dissolved and heated at 95 °C for 36 h with magnetic stirring. The corroded electrodes were washed several times with deionized water and ethanol and dried in an oven at 80 °C for overnight.
Synthesis of NiFe LDH electrode
0.39 mmol of Ni(NO3)2·6H2O, 0.37 mmol of Fe(NO3)3·9H2O, and 1.88 mmol
Characterization of the NiFeCo LDH electrode
A surface oxide layer of NF with a porous three-dimensional structure was removed through reducing heat treatment (Fig. S1). The corrosion reaction was prepared by immersing the NF electrode in an aqueous solution in which Fe(NO3)3 and Co(CH3COO)2 were dissolved, and then heating the solution at 95 °C with magnetic stirring (Fig. 1a). The corrosion process and OH– formation were the reduction potential difference of Ni2+/Ni and Fe3+/ Fe2+ and the formation of OH– trapped by the electrons
Conclusion
In summary, we have demonstrated a chemical transformation route to produce high-efficiency and cost-efficient OER and HER electrodes using a conventional metal foam as a starting material. We successfully obtained an OER electrode by the corrosion of a NF. The corroded electrode consisted of ternary NiFeCo LDH nanosheet arrays supported on the NF, and exhibited an unprecedentedly high OER activity, which could be attributed to high electrical conductivity from direct growth of the nanosheets
Author contributions
J.L., H.J., S.M.C., J.W.H. and B.L. designed the experiments. J.L., N.K. and S.W. fabricated electrodes and performed structural analyses and electrochemical measurements. N.C.S.S. and P.J.Y. contributed to phosphidation experiment. H.J. and J.W.H. performed the DFT calculations. G.S.H. and H.S.J. contributed to the solar cell experiment. J.L., Y.S.P. and S.M.C. performed the AEM water electrolysis test. N.K. and J.H.L. contributed to the data analysis. J.L. and B.L. wrote the paper. All
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by Basic Science Research Program (No. 2015R1A2A2A01006325 and 2019R1A2C2006997) and Creative Materials Discovery Program (NRF-2019M3D1A1079303) through the National Research Foundation (NRF) of Korea funded by the Ministry of Science, ICT & Future Planning.
References (57)
- et al.
Hydrous RuO2 nanoparticles as highly active electrocatalysts for hydrogen evolution reaction
Chem. Phys. Lett.
(2017) - et al.
Chemical transformation of iron alkoxide nanosheets to FeOOH nanoparticles for highly active and stable oxygen evolution electrocatalysts
J. Ind. Eng. Chem.
(2018) - et al.
A high-performance oxygen evolution electrode of nanoporous Ni-based solid solution by simulating natural meteorites
Chem. Eng. J.
(2021) - et al.
Self-assembled ultrathin NiCo2S4 nanoflakes grown on Ni foam as high-performance flexible electrodes for hydrogen evolution reaction in alkaline solution
Nano Energy
(2016) - et al.
Chimney effect of the interface in metal oxide/metal composite catalysts on the hydrogen evolution reaction
Appl. Catal. B- Environ.
(2019) - et al.
Phosphated NiCo2O4 nanoneedle arrays on flexible carbon filaments for effective oxygen evolution reaction in alkaline aqueous conditions: cooperation of small-sized effect and heteroatomic doping activation
Chem. Eng. J.
(2020) - et al.
Fabrication of FeNi hydroxides double-shell nanotube arrays with enhanced performance for oxygen evolution reaction
Appl. Catal. B- Environ.
(2020) - et al.
Integrating the active OER and HER components as the heterostructures for the efficient overall water splitting
Nano Energy
(2018) - et al.
In-situ synthesis of bimetallic phosphide with carbon tubes as an active electrocatalyst for oxygen evolution reaction
Appl. Catal. B- Environ.
(2019) - et al.
Metal-organic framework derived Co3O4/MoS2 heterostructure for efficient bifunctional electrocatalysts for oxygen evolution reaction and hydrogen evolution reaction
Appl. Catal. B- Environ.
(2019)
Nanostructuring of metal surfaces by corrosion for efficient water splitting
Chem. Phys. Lett.
Understanding the incorporating effect of Co2+/Co3+ in NiFe-layered double hydroxide for electrocatalytic oxygen evolution reaction
J. Catal.
The effects of Al substitution and partial dissolution on ultrathin NiFeAl trinary layered double hydroxide nanosheets for oxygen evolution reaction in alkaline solution
Nano Energy
Nickel doped zinc oxide nanoparticles produced by hydrothermal decomposition of nickel-doped zinc hydroxide nitrate
Particuology
Superior performance of anion exchange membrane water electrolyzer: ensemble of producing oxygen vacancies and controlling mass transfer resistance
Appl. Catal. B- Environ.
Microwave-assisted preparation of flower-like cobalt phosphate and its application as a new heterogeneous Fenton–like catalyst
Appl. Surf. Sci.
A comprehensive review on PEM water electrolysis
Int. J. Hydrogen Energy
Future cost and performance of water electrolysis: an expert elicitation study
Int. J. Hydrogen Energy
Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis
Nat. Commun.
Self-supported nanoporous Zn–Ni–Co/Cu selenides microball arrays for hybrid energy storage and electrocatalytic water/urea splitting
Chem. Eng. J.
3D porous network heterostructure NiCe@NiFe electrocatalyst for efficient oxygen evolution reaction at large current densities
Appl. Catal. B- Environ.
Cobalt-iron oxide nanoarrays supported on carbon Fiber paper with high stability for electrochemical oxygen evolution at large current densities
ACS Appl. Mater. Interfaces
Trinary layered double hydroxides as high‐performance bifunctional materials for oxygen electrocatalysis
Adv. Energy Mater.
Corrosion-engineered bimetallic oxide electrode as anode for high-efficiency anion exchange membrane water electrolyzer
Chem. Eng. J.
A superlattice of alternately stacked Ni–Fe hydroxide nanosheets and graphene for efficient splitting of water
ACS Nano
Binary FeCo oxyhydroxide nanosheets as highly efficient bifunctional electrocatalysts for overall water splitting
Chem. Eur. J.
In-situ phosphating to synthesize Ni2P decorated NiO/g-C3N4 p-n junction for enhanced photocatalytic hydrogen production
Chem. Eng. J.
Facile synthesis of flower-like a-Co(OH)2 nanostructures for electrochemical water splitting and pseudocapacitor applications
J. Ind. Eng. Chem.
Cited by (72)
A stable alkaline anion exchange membrane water electrolyzer based on a self-healing anode
2024, International Journal of Hydrogen EnergyAn integrated amorphous cobalt phosphoselenide electrocatalyst with high mass activity boosts alkaline overall water splitting
2024, Applied Catalysis B: EnvironmentalSelf-supporting trimetallic NiCoFe layered-double-hydroxide/amorphous sulfide heterostructure on nickel foam for efficient water splitting
2024, International Journal of Hydrogen Energy
- 1
These authors have contributed equally.