Growth of trimetallic CeFeNi-MOF-74 on nickel foam as a bifunctional electrocatalyst for water splitting

doi:10.21203/rs.3.rs-4815956/v1

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Growth of trimetallic CeFeNi-MOF-74 on nickel foam as a bifunctional electrocatalyst for water splitting

https://doi.org/10.21203/rs.3.rs-4815956/v1

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In order to facilitate the industrial synthesis of hydrogen from electrolytic water on a wide scale, high-performance non-precious metal electrocatalysts that can substitute precious metal electrocatalysts must be developed. This paper reports a trimetallic CeFeNi-MOF-74 electrocatalyst grown on nickel foam (NF) by solvothermal method. The introduction of trimetallics gives the metal-organic frameworks (MOFs) materials synergistic and complementary properties, resulting in better catalytic properties of the materials. Tuning the electronic structure of materials to optimize electrocatalytic performance by modulating metal ratios. It was found that the prepared Ce_0.9FeNi-MOF-74 exhibited excellent electrocatalytic activity and stability in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In 1 M KOH, the overpotential is only 262 mV for HER at a current density of 100 mA cm^− 2 and 257 mV for OER at a current density of 100 mA cm^− 2. For overall water splitting (OWS), a low voltage of only 1.68 V is required to achieve a 10 mA cm^− 2 current density. The excellent catalytic performance of Ce_0.9FeNi-MOF-74 exceeds that of many commercial catalysts. This study provides new insights into the synthesis of high-performance and stable MOF electrocatalysts.

nickel foam

hydrogen evolution reaction

metal-organic frameworks

oxygen evolution reaction

overall water splitting

Due to the environmental problems and energy scarcity caused by the long-term overuse of fossil fuels by human beings, there is an urgent need to find non-polluting, sustainable, and high energy density green energy to replace traditional fossil fuel energy sources^[1–3]. Hydrogen energy has attracted widespread attention due to its high efficiency, non-polluting and low-cost advantages^[4–5]. The electrochemical decomposition of water is an efficient way to produce high-purity hydrogen in a zero-pollution and sustainable way. Electrolysis of water involves two main reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER)^[6–7]. However, both reactions have high energy barriers, especially the slow kinetics of the OER, limiting their industrial large-scale application. As a result, effective catalysts are required to aid the reaction by lowering the reaction barrier and accelerating the reaction kinetics^[8]. Generally, precious metal Pt-based catalysts and precious metal oxide RuO₂ are considered to be the most effective catalysts for HER and OER, respectively, but the scarcity and high price of precious metals have prevented the large-scale application of hydrogen production from electrolytic water in industry. Therefore, it is necessary to design and prepare a bifunctional non-precious metal electrocatalyst with high efficiency and low cost^[9–11].

Non-precious metal catalysts, including metal oxides, sulfides, phosphides, hydroxides, and other compounds that show strong catalytic activity in alkaline media, have been the subject of intensive investigation in the past few years^[12]. Among them, Metal-organic frameworks (MOFs) have received a lot of attention in the electrochemical decomposition of water, and they are usually formed by the coordination of metal ions and organic ligands. The structure of metal-organic frameworks can be regulated by modulating metal cations and ligands and has the advantages of high porosity, large specific surface area, and structural diversity. This provides a large number of metal active sites for electrochemical catalytic reactions^[13–16]. Therefore, it is a promising electrocatalyst for a wide range of applications. Pristine MOF materials have poor electrical conductivity and are less stable, so MOFs are usually used as precursors to form porous carbon materials or various metal compounds by pyrolysis to enhance the catalyst activity^[17–19]. Nevertheless, the electrocatalytic activity is limited by active site reduction and catalyst morphology change during pyrolysis due to the blockage of metal active sites by organic ligands and degradation of the MOF backbone structure^[20–21]. It has been demonstrated that MOFs can exist with mixed metal ions in their structures and coexist, giving the catalysts an abundance of active sites, good stability, and excellent electrical conductivity. Compared to monometallic MOFs, polymetallic MOFs have superior performance in electrocatalysis, which may be due to the synergistic effects of two or more metals^[22]. Among the many types of MOFs, MOF-74 has been extensively studied and consists of divalent transition metals (M = Mg, Fe, Cu, Ni) coordinated to the organic ligand 2,5-dihydroxyterephthalic acid (DHTA)^[23]. In addition, the construction of self-supporting electrodes is also a method to improve the electrocatalytic performance of MOFs. Nickel Foam (NF) has good electrical conductivity and porous structure and is often used as a collector, which can synergize with MOFs to effectively resist bubble generation and expose more active sites, resulting in improved catalyst stability and activity, and can be used directly as an electrode^[24]. For example, Chen et al. grew NiFe-MOF-74 nanosheets on NF by a one-step solvothermal process. Thin MOF shapes are obtained by synergistic interaction of two metals, Fe and Ni, to increase the visibility of active sites. At a current density of 10 mA cm^− 2, the OER and HER overpotentials were 208 mV and 195 mV, respectively, showing excellent activity and stability^[25].

Rare earth ions have higher coordination numbers and richer coordination geometries than transition metal ions and have a strong coordination ability with organic ligands, which is conducive to the stabilization of the frameworks, while the variable coordination of rare earth ions can regulate the pore size and surface area of the frameworks^[26–27]. Among the many rare earth elements, the rare earth Ce is a highly conductive metal with more abundant reserves than transition metals. Because of its exceptional oxygen reduction capabilities and flexible coordination, rare earth cerium plays a significant role in adjusting the electronic structure of multimetallic electrocatalysts. Using the unique 4f orbitals of rare earth elements, doping rare earth Ce into transition metal-based electrocatalytic materials can not only modulate the electronic structure on the surface of the materials to make them have more active sites but also increase the conductivity of the materials and optimize the energy of the OER intermediates, which can effectively improve the activity and optimize the stability of the catalysts^[28].

Herein, we report the growth of trimetallic Ce_xFeNi-MOF-74 (x = Ce as a percentage of total feed) on nickel foam as a bifunctional electrocatalyst for water decomposition using a solvothermal method. Study of electrocatalytic activity by modulation of the metal ratio of Ce and Fe. The optimized trimetallic Ce_0.9FeNi-MOF-74 was found to have excellent electrocatalytic activity and stability. The best Ce_0.9FeNi-MOF-74 exhibited low 257 mV overpotentials and 262 mV overpotentials for OER and HER at a current density of 100 mA cm^− 2 and remained electrochemically stable for 60 hours. This work provides a new idea for designing MOF-based catalysts with excellent performance and stability.

1.1 Chemicals

All chemicals are of analytical grade and can be used without further purification. Cerium(III) nitrate hexahydrate(Ce(NO₃)₃·6H₂O)、Iron(II) chloride tetrahydrate(FeCI₂·4H₂O)、N,N-dimethylformamide(HCON(CH₃)₂)、2,5-Dihydroxytereph-thalic acid(DOBDC)、Ethanol、Nafion solution(5 wt %)、Ruthenium(IV) oxide(RuO₂ 99.9%)、Platinum on carbon(Pt/C, 20 wt %)、Nickel foam(NF)。

1.2 Preparation of Ce_xFeNi-MOF-74

First, Ce(NO₃)₃·6H₂O and FeCI₂·4H₂O were proportionally dissolved in 7.5 mL of dimethylformamide (DMF) and 970 µL of ethanol (The total content was 1.75 mmol and the feeding ratios Ce: Fe were 1:1, 3:1, 6:1, 9:1, 1:0, respectively.) and stirred for 10 min to form solution A. Dissolve 2,5-dihydroxyterephthalic acid in 7.5 mL of DMF to form solution B. Ultrasonic NF (1cm x 2cm) in 3M hydrochloric acid solution for 10min to remove surface grease and oxides. Wash with ethanol and deionized water after sonication and dry at room temperature. Transfer the cleaned nickel foam to solution A and sonicate for 5 min, then pour solution B into solution A where the nickel foam is placed, and sonicate for 5 min. The mixed solution and nickel foam were transferred to an autoclave, heated to 120°C, and kept for 24 h. After cooling to room temperature, the nickel foam in the reaction kettle was taken out and rinsed three times with DMF and ethanol, and then dried under vacuum at 40°C for 30 min to obtain Ce_xFeNi-MOF-74. The prepared CexFeNi-MOF-74 can be directly used as a working electrode.

1.3 Preparation of Ni foam supported Pt/C and IrO₂ electrode

4 mg of Pt/C (20 wt %) powder was dissolved in a mixture of 100 µL of water, 100 µL of ethanol and 10 µL of Nafion solution. The mixed solution was sonicated for 10 min, and then the solution was coated on the cleaned NF (1 cm × 2 cm) and dried at room temperature to obtain the Pt/C/NF electrode. RuO₂/NF electrodes were prepared by replacing Pt/C with RuO₂ (99.9%) using the same approach。

1.4 Characterization

Scanning electron microscope (SEM, JEOL JSM-6510LV) was used to observe the morphology, size and particle size of the samples. The use of Energy Dispersive Spectroscopy (EDS) allows preliminary information on the elemental composition and content of the sample surface to be obtained. Study of the elemental composition and chemical state of samples by X-ray photoelectron spectroscopy (XPS, Escalab 250Xi, Thermo). Structural and physical analyses of samples by X-ray diffraction (XRD, Rigaku D/max-rA).

1.5 Electrochemical Measurements

All OER and HER electrocatalytic properties were tested in room temperature 1M KOH solution using a CHI660E electrochemical workstation under a three-electrode system. The ready samples served as functional electrodes, Ag/AgCl as electrodes of reference, platinum sheets were used as counter electrodes for OER and graphite rods were used as counter electrodes for HER. Adjustment of all potentials to the reversible hydrogen electrode (RHE) by performing calibration experiments.

To stabilize the electrode, 50 cycles of cyclic voltammetry (CV) at a scan rate of 0.1 mV·s-1 were performed. Next, linear sweep voltammetry (LSV) at a scan rate of 5 mV·s-1 was performed. To account for solution resistance losses, 95% iR compensation is applied to all polarization curves. According to the Nernst equation : E_RHE=E_Ag/AgCl + 0.21 + 0.059 × pH. Conversion of the measured potential to the potential of the reversible hydrogen electrode. The OER and HER overpotentials (η) were calculated according to the following equations: η(V) = E_RHE − 1.23V and η(V) = E_RHE. Electrochemical Impedance Spectroscopy (EIS) testing from 100kHz − 0.01kHz. By CV to estimate the electrochemical active surface area (ECSA) of the electrodes with scanning rates of 20、50、80、100、150 and 200mV·s^− 1. Testing the stability of materials at a current density of 100 mA cm^− 2 using the chronopotential method.

Figure 1 shows a schematic of the preparation of Ce_xFeNi-MOF-74. In situ growth of Ce_xFeNi-MOF-74 on nickel foam by the solvothermal method using Ce(NO₃)₃·6H₂O as Ce source, FeCI₂·4H₂O as Fe source and nickel foam as substrate. During solvent heating, Fe²⁺ is easily oxidized and Ni²⁺ is released from the nickel foam by the etching action of Fe³⁺ and Ce³⁺. Growth of trimetallic MOFs on nickel foam by coordination of metal cations with the organic ligand 2,5-dihydroxyterephthalic acid. The electrochemical properties of Ce_xFeNi-MOF-74 with different metal ratios were investigated by modulating the feeding metal ratio.

3.1 Material Characterization

Use of XRD to characterize the crystal structure of Ce_xFeNi-MOF-74. Figure 2 shows the XRD spectra of all scaled samples of Ce_xFeNi-MOF-74. As can be seen from Fig. 2, characteristic diffraction peaks appear at 44.4° and 51.8° for all proportions of the samples, corresponding to the (1 1 1) and (2 0 0) crystal planes of nickel metal, respectively^[29]. In addition, Ce_0.5FeNi-MOF-74, Ce_0.75FeNi-MOF-74, Ce_0.86FeNi-MOF-74, and Ce_0.9FeNi-MOF-74 showed characteristic diffraction peaks at 6.9° and 11.8°, which corresponded to the (1 1 0) and (3 0 0) crystalline surfaces of the MOF-74, respectively, and there were no other apparent stray peaks^[30]. This proves the existence of MOF-74. However, for CeNi-MOF-74, no peaks other than the characteristic peaks of nickel foam appeared, which was due to the strong self-nucleation ability of CeNi-MOF-74 and poor crystallinity on nickel foam, so the diffraction peaks of MOF-74 could not appear. The successful growth of MOF-74 on nickel foam was demonstrated by XRD tests.

The morphology of Ce_0.9FeNi-MOF-74 was analyzed using SEM. As shown in Fig. 3 (a-c), Ce_0.9FeNi-MOF-74 appeared on the surface of the NF agglomeration phenomenon, round sphere agglomerates attached to the surface of the NF, the diameter of the round sphere is about 1.5 µm and its surface is uneven, which indicates that Ce_0.9FeNi-MOF-74 has been successfully grown on the nickel foam. As shown in Fig. 3(d, e), smaller diameter rice-like particles are also formed between the circular spheres, which are connected to each other. These structural distributions have the potential to increase the material's specific surface area and expose more active sites, hence increasing electrolytic water catalysis. Characterization of catalyst elemental distribution by EDS. As can be seen in Fig. 3(f), Ce, Fe, Ni and C are uniformly distributed in Ce_0.9FeNi-MOF-74. Metal Ce and Fe do not exist in a position where the elements are particularly abundant, indicating that no nanoparticles are attached to Ce_0.9FeNi-MOF-74. The metals Ce and Fe are present in Ce_0.9FeNi-MOF-74 as nodes, not oxides or otherwise attached to the surface of Ce_0.9FeNi-MOF-74. Metal Ni is also uniformly distributed in the material, which is since during the hydrothermal reaction, Ce³⁺ and Fe²⁺ are oxidized to Fe³⁺ and corrode some of the nickel foam, while metal Ni is oxidized to Ni²⁺, which is involved in the construction of MOF-74. The uniform distribution of elements can effectively increase the active specific surface area of the catalyst, thus improving the catalytic activity^[31].

The electrical structure and chemical valence states of the Ce_0.9FeNi-MOF-74 catalyst were characterized using XPS. The entire spectrum of Ce_0.9FeNi-MOF-74 is displayed in Fig. 4(a), which shows that the catalyst contains the coexistence of elements such as Ce, Fe, Ni and C, which concurs with the EDS elemental outcomes. Figure 4(b) shows the high-resolution XPS spectra of Ce 3d. Two prominent peaks are seen at 884.48 eV and 902.53 eV, which correlate to Ce 3d_5/2 and Ce 3d_3/2, respectively. Furthermore, Two satellite peaks may be found at 880.32 and 899.33 eV, showing that Ce³⁺ is present. The high-resolution XPS spectra of Fe 2p are displayed in Fig. 4(c). Fe 2p_3/2 and Fe 2p_1/2 have two principal peaks, respectively, that are found at 711.23 eV and 721.88 eV, and satellite peaks can be found at 704.98 eV and 717.53 eV, respectively. These peaks suggest the presence of Fe²⁺ and Fe³⁺ in Ce_0.9FeNi-MOF-74. This is because in the hydrothermal reaction process, due to the oxygen contained in the reactor, under high temperature and pressure part of the Fe²⁺ will be oxidized to Fe³⁺. It has been shown that the Fe (II) -O-Fe (III) structure can effectively stabilize the high-valent metal sites at the atomic level, thus improving the OER properties. Figure 4(d) shows the high-resolution XPS spectra of Ni 2p, detecting the presence of two main peaks at 854.68 eV and 872.03 eV, which are attributed to Ni 2p_3/2 and Ni 2p_1/2, with the peaks at 859.93 eV and 880.88 eV being the satellite peaks of Ni. This demonstrates the presence of Ni²⁺, and it is noteworthy that a characteristic peak of metallic Ni was observed at 851.03 eV, attributed to the nickel foam substrate. The successful growth of Ce_0.9FeNi-MOF-74 on NF was further demonstrated by XPS analysis, which also proved that Ce³⁺, Fe³⁺, Fe²⁺ and Ni²⁺ metal ions coexisted in the material, and that the multiple valence metals were able to diversify the electronic NF structure of the material and collaborate to promote the reaction during OER and HER^[32].

3.2 Electrochemical performances

To investigate the OER catalytic mechanism of Ce_xFeNi-MOF-74, Ag/AgCl was utilized as the reference electrode in a standard three-electrode setup to evaluate the OER catalytic efficacy of Ce_xFeNi-MOF-74, platinum sheet serving as the opposing electrode, and Ce_xFeNi-MOF-74 grown in situ on NF as the working electrode in 1 M KOH solution. Figure 5(a) shows the polarization curves of Ce_xFeNi-MOF-74 and RuO₂ prepared with different metal ratios compensated by 95% IR, and it can be seen that all the synthesized Ce_xFeNi-MOF-74 exhibit good OER catalytic performance, which is superior to commercial RuO₂ catalysts. The OER catalytic performance of Ce_xFeNi-MOF-74 can be effectively regulated by varying the feeding ratios of Ce and Fe, in which Ce_0.9FeNi-MOF-74 exhibits the most excellent OER performance. As illustrated in Fig. 4(b), the overpotential of Ce_0.9FeNi-MOF-74 requires only 257 mV at 100 mA cm^− 2 current density, which is less than RuO₂ (413mV)、Ce_0.86FeNi-MOF-74(276mV)、Ce_0.75FeNi-MOF-74(277mV)、Ce_0.5FeNi-MOF-74(263mV) and CeNi-MOF-74(320mV). To learn more about the mechanics of OER, the Tafel slope was calculated from the polarization curve. It is evident from Fig. 4(c) that Ce_0.9FeNi-MOF-74 has a substantially smaller Tafel slope than the other materials, with a Tafel slope of only 30.9mV·dec^− 1, whereas the Tafel slopes of CeNi-MOF-74 are 54.1 mV·dec^− 1, and those of RuO₂ are 33.1 mV·dec^− 1. Further understanding of the electrode kinetics and surface impedance of materials by measuring electrochemical impedance (EIS). As shown in Fig. 4(d) and Table 1, Ce_0.9FeNi-MOF-74 exhibits the lowest solution resistance (R_s=1.62 Ω) and the lowest charge transfer resistance (R_ct=1.25 Ω) compared to other metal ratios, demonstrating that Ce_0.9FeNi-MOF-74 has a much faster electron and material transfer process and excellent electrical conductivity. Figure 5(e) shows the polarization curves of Ce_0.9FeNi-MOF-74 before and after 1000 CV cycles. In addition, the stability of the material was tested using the chronopotential method (CP) at a current density of 100 mA cm^− 2, and the outcomes are displayed in Fig. 5(f), after 60 h of the chronopotential test, there is no significant change in the voltage, which indicates that Ce_0.9FeNi-MOF-74 has a good stability.

Table 1

EIS results of Ce_xFeNi-MOF-74 with different metal ratios
Catalysts	R_s(Ω)	R_ct(Ω)
Ce_0.9FeNi-MOF-74	1.62	1.25
Ce_0.86FeNi-MOF-74	1.95	1.89
Ce_0.75FeNi-MOF-74	2.01	1.71
Ce_0.5FeNi-MOF-74	1.95	1.57
CeNi-MOF-74	1.8	15.32

Using graphite rods as counter electrodes, HER catalytic activity tests were conducted on different materials. Figure 6(a) shows the polarization curves of Ce_xFeNi MOF-74 and 20% Pt/C for all metal ratios. As shown in Fig. 6(b), among the Ce_xFeNi-MOF-74 and 20% Pt/C prepared with all metal ratios, Ce_0.9FeNi-MOF-74 requires only 262 mV overpotential at 100 mA cm^− 2 current density, which is superior to Ce_0.86FeNi-MOF-74 (356mV)、Ce_0.75FeNi-MOF-74 (303mV)、Ce_0.5FeNi-MOF-74 (273mV) and CeNi-MOF-74 (320mV). However, At a current density of 100 mA cm-2, it is marginally more than the 239 mV overpotential of the commercial 20% Pt/C catalyst, which suggests that Ce_0.9FeNi-MOF-74 has excellent catalytic activity. Figure 6(c) shows that all Ce_xFeNi-MOF-74 have low Tafel slopes, and the Tafel slopes are all around 100 mV·dec^− 1. Proof that the Volume step determines the rate of the catalytic reaction. Ce_0.9FeNi-MOF-74 possesses the lowest Tafel slope of 86.4 mV·dec^− 1, demonstrating that Ce_0.9FeNi-MOF-74 has the fastest charge transfer kinetic process. Evaluation of electrode reaction kinetics by EIS test. As shown in Fig. 6 (d) and Table 2, Ce_0.9FeNi-MOF-74 shows the lowest solution resistance (R_s=1.72 Ω) and the lowest charge transfer resistance (R_ct=3.72 Ω). This implies that Ce_0.9FeNi-MOF-74 has a smaller charge transfer resistance and faster charge transfer kinetics in the HER process, and thus Ce_0.9FeNi-MOF-74 exhibits excellent HER performance. Figure 6(e) shows the Ce_0.9FeNi-MOF-74 polarisation curves before and after 1000 CV cycles. Stability of Ce_0.9FeNi-MOF-74 by CP at 100 mA cm^− 2 current density. The results are shown in Fig. 6(f). In the 60 h test, there were only some slight increases in the overpotential, indicating that Ce_0.9FeNi-MOF-74 has a more stable HER catalytic performance.

Table 2

EIS results of Ce_xFeNi MOF-74 with different metal ratios
Catalysts	R_s(Ω)	R_ct(Ω)
Ce_0.9FeNi-MOF-74	1.72	3.72
Ce_0.86FeNi-MOF-74	2.28	4.19
Ce_0.75FeNi-MOF-74	1.72	7.24
Ce_0.5FeNi-MOF-74	1.8	8.84
CeNi-MOF-74	1.75	23.41

Combining the above electrochemical activity tests, it can be shown that Ce_0.9FeNi-MOF-74 possesses excellent OER and HER catalytic properties. Ce_0.9FeNi-MOF-74 as cathode and anode assembled into a two-electrode system (Ce_0.9FeNi-MOF-74 // Ce_0.9FeNi-MOF-74). It is testing the overall water splitting of Ce_0.9FeNi-MOF-74 in 1 M KOH solution. Figure 7(a) shows the LSV curves of the fully solvated water of Ce_0.9FeNi-MOF-74. It is evident that a current density of 10 mA cm-2 can be attained with a low voltage of just 1.68 V, which proves that Ce_0.9FeNi-MOF-74 has a good catalytic performance for overall water splitting. Tests of the overall water splitting stability of Ce_0.9FeNi-MOF-74 using CP at a current density of 10 mA cm^− 2. Figure 7(b) shows that the overpotential of Ce_0.9FeNi-MOF-74 remained essentially stable during the 60h test, indicating that Ce_0.9FeNi-MOF-74 has excellent overall water splitting stability.

ECSA is an important factor in assessing the activity of electrocatalysts. ECSA is proportional to the double layer capacitance (C_dl). Therefore, ECSA is reflected by the double layer capacitance. To investigate the reason for the excellent OER catalytic activity of Ce_xFeNi-MOF-74, different metal ratios of Ce_xFeNi-MOF-74 were tested for cyclic voltammogram (CV) in the non-Faraday region at different scan rates. Bilayer capacitance value obtained after fitting. ECSA is estimated by the following formula: ECSA = C_dl/C_s (C_s=0.04µF·cm^− 2). The results are shown in Fig. 8. Ce_0.9FeNi-MOF-74 shows the highest C_dl=4.16 mF·cm^− 2. Ce_0.75FeNi-MOF-74 shows the lowest C_dl=2.7 mF·cm^− 2. It was shown that Ce_xFeNi-MOF-74 had higher ECSA with the increase of the proportion of input Ce, exposing more active sites and thus improving the OER electrocatalytic activity of the material, but the C_dl value of CeNi-MOF-74 was second only to that of Ce_0.9FeNi-MOF-74, which indicated that the doping of Fe changed the intrinsic activity of CeNi-MOF-74. Experiments have shown that the electrochemically active specific surface area of the material can be effectively modulated by varying the metal feeding ratio, which affects the catalytic activity of Ce_xFeNi-MOF-74。

In summary, trimetallic Ce_xFeNi-MOF-74 was grown in situ on NF by solvothermal method, and its electrocatalytic properties were investigated by modulating the metal feeding ratio. First, Ce_0.9FeNi-MOF-74 was successfully grown on NF, as shown by SEM observations, and the catalyst surface was rough, which significantly improved the catalysts' specific surface area. XPS confirms the coexistence of Ce³⁺, Fe³⁺, Fe²⁺ and Ni²⁺ in the catalysts and their collaboration with each other. Secondly, the catalyst was tested for electrochemical activity. The results show that Ce_0.9FeNi-MOF-74 has excellent OER and HER catalytic activity and stability. At 100 mA cm^− 2 current density, the overpotentials of OER and HER were 257 mV and 262 mV, respectively, which were superior to those of commercial noble metal catalysts. In the 60h CP test, there is no significant change in its voltage and it has good stability. The excellent electrochemical properties and stability of Ce_0.9FeNi-MOF-74 are attributed to the synergistic interaction between the multi-metals, which diversifies the electronic results of the material and exposes more active sites. The present work advances a novel concept for the synthesis of effective polymetallic MOF-based catalysts for the electrolysis of water.

Conflicts of interest

There are no conflicts to declare.

Author Contribution

Jun Zhang, Tao Long and GuangHuan Li made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data; or the creation of new software used in the work;Yangwen Liu, Zilang Zhong , Yang Zhang and XuChang Chen drafted the work or revised it critically for important intellectual content;GuangHuan Li and Tao Long approved the version to be published;Jun Zhang ,Tao Long, Yangwen Liu, Zilang Zhong, Yang Zhang, XuChang Chen and GuangHuan Li agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Acknowledgments

This work is financially supported by the Guangdong Basic and Applied Basic Research Foundation (2024A1515010372), the Projects of Talents Recruitment of GDUPT (520107, 72100003145), the Science and Technology Innovation Strategic Project of Guangdong Province (2023S005049) and the Project Talent Innovation for GDUPT (923300007).

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You are reading this latest preprint version

Growth of trimetallic CeFeNi-MOF-74 on nickel foam as a bifunctional electrocatalyst for water splitting

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental

1.1 Chemicals

1.2 Preparation of Ce_xFeNi-MOF-74

1.3 Preparation of Ni foam supported Pt/C and IrO₂ electrode

1.4 Characterization

1.5 Electrochemical Measurements

3. Results and discussion

3.1 Material Characterization

3.2 Electrochemical performances

4. Conclusion

Declarations

Conflicts of interest

Author Contribution

Acknowledgments

References

Additional Declarations

Status:

Version 1

Growth of trimetallic CeFeNi-MOF-74 on nickel foam as a bifunctional electrocatalyst for water splitting

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental

1.1 Chemicals

1.2 Preparation of CexFeNi-MOF-74

1.3 Preparation of Ni foam supported Pt/C and IrO2 electrode

1.4 Characterization

1.5 Electrochemical Measurements

3. Results and discussion

3.1 Material Characterization

3.2 Electrochemical performances

4. Conclusion

Declarations

Conflicts of interest

Author Contribution

Acknowledgments

References

Additional Declarations

Status:

Version 1

1.2 Preparation of Ce_xFeNi-MOF-74

1.3 Preparation of Ni foam supported Pt/C and IrO₂ electrode