Development of highly active, durable, bifunctional electrocatalysts for overall water splitting is of great importance to enhance the use of hydrogen energy. Herein, we synthesize a porous and interfaces-rich Fe3O4/RuO2-C composite from the Metal organic frameworks (MOF) material for overall water splitting in alkaline media. The Fe3O4/RuO2-C catalyst showed superior oxygen evolution reaction (OER) with high faradic efficacy. It requires 268 mV overpotential to achieve the current density of 20 mA/cm2. The catalyst also exhibited good hydrogen evolution reaction (HER) with a current density of 10 mA/cm2 at an overpotential of 94 mV. The stability test confirmed a remarkable long-term OER and HER stability of this catalyst in alkaline media. In addition, the Fe3O4/RuO2-C catalyst was also used as cathode and anode material for overall water splitting. It showed superior activity and stability in alkaline media with 10 mA/cm2 current density at 1.595 V cell potential. The excellent electrocatalytic activity of the Fe3O4/RuO2-C catalyst can be attributed to its porous structure, synergistic interaction between the components, the presence of hetero-interfaces, high electrochemical surface area etc. This work may provide an opportunity to design a bifunctional electrocatalyst for the development of anion exchange membrane water electrolyzers (AEMWEs).
Hydrogen production from water electrolysis is of great interest for attaining sustainable clean energy storage and conversion, but the required working voltage (>1.23 V) in water splitting limits its applications in industrial expansion. Therefore, replacing the oxygen evolution reaction (OER) with a more favorable anodic oxidation reaction, which can provide more valuable products and less working voltage, will be of great significance for the upcoming expansion of hydrogen production in industrial applications. In this report, a two-dimensional (2D) amorphous sheet-like nickel oxide encapsulated on the nitrogendoped carbon (NiO x /CN x ) composite was synthesized for the urea oxidation reaction (UOR) and ethanol oxidation reaction (EOR). Remarkably, the catalyst shows 1.647, 1.378, and 1.354 V vs. reversible hydrogen electrode (RHE) potential at 10 mA/cm 2 current density for OER, UOR, and EOR, respectively, with good stability. The overall water, urea, and ethanol electrolyses of NiO x /CN x were carried out by coupling with commercial Pt/C as a cathode which shows only 1.626, 1.43, and 1.414 V cell potential at 20 mA/cm 2 current density. The catalyst also shows excellent chronopotentiometric and dynamic stability toward all the electrolyses. The high catalytic activity of NiO x /CN x may be attributed to the synergistic interaction between the support and materials, amorphous structure, 2D sheet-like morphology, porous structure, and high electrochemical surface area. This finding shows that NiO x /CN x nanosheets can replace noble metal-based catalysts for efficient anodic oxidation reactions.
The design and synthesis of one-dimensional (1D) metal–organic frameworks (MOFs) with a high surface area are crucial for their potential usage in supercapacitor applications. 1D-Ni-MIL-77 MOF, synthesized by a one-step solvothermal method, is used here to investigate its activity in supercapacitor applications. High surface-to-volume ratios and short ion diffusion path lengths in 1D-structured nanomaterials result in high charge/discharge rates. 1D-Ni-MIL-77 MOF nanobelts show a high surface area of 93.48 m2 g–1 that gives ample active electrochemical sites. 1D-Ni-MIL-77 shows a specific capacitance (C) value of 1376 F g–1 under the current of 1 A g–1. Additionally, an asymmetric supercapacitor (ASC) was assembled by employing activated carbon as the negative electrode and a 1D-Ni-MIL-77 nanobelt as the positive electrode. With the assembled ASC, at a power density of 750 W kg–1, an energy density of 25 W h kg–1 was attained with a voltage ranging from 0 to 1.5 V. The cyclic durability of the ASC was examined, and it exhibited excellent retention of 95% of its initial capacitance after 5000 cycles.
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