Partner: Goddati Mahendra |
Recent publications
1. | Birhanu Bayissa G.♦, Teshome Tufa L.♦, Mahendra G.♦, Lee Y.♦, Fikadu Banti B.♦, Nwaji Njoku N., You S.♦, Lee J.♦, Oxygen Vacancy Generation and Stabilization in Layered NiFeCo Double Hydroxide Nanosheets for a Highly Efficient Oxygen Evolution Reaction, ACS Applied Nano Materials, ISSN: 2574-0970, DOI: 10.1021/acsanm.4c01840, Vol.8, pp.A-K, 2024 Abstract: Oxygen vacancy (Vo) is ubiquitous, playing a critical role in tuning the electronic configuration and optimizing the adsorption of adsorbates in the oxygen evolution reaction (OER) process. However, fine control over the density and stabilization of Vo is a big challenge in the highly oxidizing environment of OER. Herein, we have fabricated bulk NiFeCo (layered double hydroxide) LDHs via the hydrothermal method and exfoliated them into thin sheets rich with Vo using high-energy Ar-plasma. We doped fluoride to simultaneously modulate the charge distribution of surrounding atoms and stabilize Vo by taking advantage of the extremely high electronegativity and similar ion diameter to oxygen of fluoride. The material exhibited OER activity with a low overpotential of 200 mV at 10 mA cm–2 and a Tafel slope of 34.6 mV dec–1. Density functional theory (DFT) calculations support the claim that Vo and fluoride substantially increase NiFeCo LDH OER activity by modifying the electronic structures of the catalytically active sites. Keywords:Electrocatalyst, Double layered hydroxide, oxygen evolution reaction, oxygen vacancy, stabilization Affiliations:
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2. | Nwaji Njemuwa N.♦, Juyong G.♦, Mahendra G.♦, Hyojin K., Adewale Hammed P.♦, Sharan A.♦, Singh N.♦, Lee J.♦, Defect engineered Fe3C@NiCo2S4 trojan nanospike derived from Metal Organic framework as Advanced electrode material for Hybrid supercapacitor., ACS Applied Materials and Interfaces, ISSN: 1944-8244, DOI: 10.1021/acsami.3c04635, Vol.15, No.29, pp.34779-34788, 2023 Abstract: The rational synthesis and tailoring of metal-organic frameworks (MOFs) with multifunctional micro/nanoarchitectures have emerged as a subject of significant academic interest owing to their promising potential for utilization in advanced energy storage devices. Herein, we explored a category of three-dimensional (3D) NiCo2S4 nanospikes that have been integrated into a 1D Fe3C microarchitecture using a chemical surface transformation process. The resulting electrode materials, i.e., Fe3C@NiCo2S4 nanospikes, exhibit immense potential for utilization in high-performance hybrid supercapacitors. The nanospikes exhibit an elevated specific capacity (1894.2 F g-1 at 1 A g-1), enhanced rate capability (59%), and exceptional cycling stability (92.5% with 98.7% Coulombic efficiency) via a charge storage mechanism reminiscent of a battery. The augmented charge storage characteristics are attributed to the collaborative features of the active constituents, amplified availability of active sites inherent in the nanospikes, and the proficient redox chemical reactions of multi-metallic guest species. When using nitrogen-doped carbon nanofibers as the anode to fabricate hybrid supercapacitors, the device exhibits high energy and power densities of 62.98 Wh kg-1 and 6834 W kg-1, respectively, and shows excellent long-term cycling stability (95.4% after 5000 cycles), which affirms the significant potential of the proposed design for applications in hybrid supercapacitors. The DFT study showed the strong coupling of the oxygen from the electrolyte OH- with the metal atom of the nanostructures, resulting in high adsorption properties that facilitate the redox reaction kinetics. Keywords:defect engineering,Nanospike,advanced electrode,hybrid,MOF,Supercapacitor Affiliations:
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3. | Mahendra G.♦, Huu-Quang N.♦, Sohyun K.♦, Birhanu Bayissa G.♦, Teshome Tufa L.♦, Nwaji Njemuwa N., My-Chi Thi N.♦, Juyong G.♦, Lee J.♦, Rugged forest morphology of magnetoplasmonic nanorods that collect maximum light for photoelectrochemical water splitting, Nano Micro Small Journal, ISSN: 1613-6829, DOI: 10.1002/smll.202302980, Vol.19, pp.1-14, 2023 Abstract: A feasible nanoscale framework of heterogeneous plasmonic materials and
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4. | Nwaji Njemuwa N.♦, Hyojin K.♦, Mahendra G.♦, Teshome Tufa L.♦, Juyong G.♦, Sharan A.♦, Singh N.♦, Lee J.♦, Sulfur vacancy induced Co3S4@CoMo2S4 nanocomposite as functional electrode for high performance supercapacitor, Journal of Materials Chemistry A, ISSN: 2050-7488, DOI: 10.1039/d2ta08820g, Vol.11, pp.3640-3652, 2023 Abstract: Vacancy engineering offers an attractive approach to improving the surface properties and electronic
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