Browsing by Author "Seung Hee Lee"

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Potentialities of nanostructured SnS2 for electrocatalytic water splitting: A review
(Elsevier Ltd, 2022) Rajneesh Kumar Mishra; Gyu Jin Choi; Hyeon Jong Choi; Jay Singh; Seung Hee Lee; Jin Seog Gwag
Evolving economically affordable, scalable, and effective electrocatalysts for producing viable hydrogen energy through electrocatalytic water splitting are highly desirable due to depleting fossil fuels and growing ecological and environmental concerns. Recently, layered SnS2 semiconductor nanomaterial has been recognized as a noteworthy electrocatalytic candidate due to its chemically stable, high effective surface area, low cost, and high stability. This review discussed how to boost hydrogen energy production using layered SnS2 nanostructure as catalysts through electrocatalytic water splitting, which essentially comprises morphological, doping, and nanocomposite/ heterostructural engineering. Further, various vital parameters for evaluating the electrocatalytic properties of layered SnS2 and reaction mechanisms are broadly discussed. Finally, we also discussed the summary and the future perspectives of evolving layered SnS2 nanostructure as a superior electrode nanomaterial for electrocatalytic hydrogen evolution reaction. © 2022 Elsevier B.V.
Recent advances in ZnO nanostructure as a gas-sensing element for an acetone sensor: a short review
(John Wiley and Sons Ltd, 2023) Rajneesh Kumar Mishra; Vipin Kumar; Le Gia Trung; Gyu Jin Choi; Jeong Won Ryu; Rajesh Bhardwaj; Pushpendra Kumar; Jay Singh; Seung Hee Lee; Jin Seog Gwag
Air pollution is a severe concern globally as it disturbs the health conditions of living beings and the environment because of the discharge of acetone molecules. Metal oxide semiconductor (MOS) nanomaterials are crucial for developing efficient sensors because of their outstanding chemical and physical properties, empowering the inclusive developments in gas sensor productivity. This review presents the ZnO nanostructure state of the art and notable growth, and their structural, morphological, electronic, optical, and acetone-sensing properties. The key parameters, such as response, gas detection limit, sensitivity, reproducibility, response and recovery time, selectivity, and stability of the acetone sensor, have been discussed. Furthermore, gas-sensing mechanism models based on MOS for acetone sensing are reported and discussed. Finally, future possibilities and challenges for MOS (ZnO)-based gas sensors for acetone detection have also been explored. © 2022 John Wiley & Sons Ltd.
Unveiling the Transformative Potential of SWCNT/In2O3 Heterostructures as High-Performance Catalysts for Overall Water Splitting
(American Chemical Society, 2023) Rajneesh Kumar Mishra; Gyu Jin Choi; Jeong Won Ryu; Jay Singh; Santosh Kumar; Yogendra Kumar Mishra; Seung Hee Lee; Jin Seog Gwag
In this paper, we studied the synthesis of In2O3/SWCNT heterostructure catalysts by blending single-walled carbon nanotubes (SWCNTs) in In2O3 nanomaterial during an in situ and facile one-step hydrothermal method for the application of electrocatalytic overall water splitting (OWS). Interestingly, it is predictable that the SWCNTs and In2O3 have different vacuum levels, which could play a crucial role in charge transfer by band engineering when both are brought into direct contact (surface or interface or both) to form the In2O3/SWCNT heterostructure. Remarkably, we discussed the possibilities of surface and interface engineering during In2O3/SWCNT heterostructure formation, which regulates and enhances the hydrogen and oxygen reaction kinetics. Consequently, the In2O3/SWCNT-4 catalyst illustrates the lowest overpotential values of 337 and 141 mV during the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, compared with other catalysts in an alkaline medium. It may be because adding SWCNTs accelerates the mass transport and segregation of water molecules and enriches the adsorption and desorption free energy of hydrogen intermediates, providing more active sites and improving intrinsic catalytic activities. The Tafel slope values of the OER are 175.1 and 116.1 mV dec-1 for the pure In2O3 catalyst and In2O3/SWCNT-4 (5.0 mL of SWCNTs) heterostructure catalyst, suggesting that the SWCNTs can regulate the charge-transfer rate, which can play a crucial role in determining the rate-controlling steps of oxygen and hydrogen evolution reactions. The In2O3/SWCNT-4 catalyst shows excellent stability over 24 h of the HER (at −10 mA cm-2) and 24 h of the OER (at 10 mA cm-2) using chronopotentiometry (CP). Further, the overall water splitting of the In2O3/SWCNT-4
Voltage holding and self-discharge phenomenon in ZnO-Co3O4 core-shell heterostructure for binder-free symmetric supercapacitors
(Elsevier B.V., 2022) Rajneesh Kumar Mishra; Gyu Jin Choi; Hyeon Jong Choi; Jay Singh; Fateme Sadat Mirsafi; Horst-Günter Rubahn; Yogendra Kumar Mishra; Seung Hee Lee; Jin Seog Gwag
We report an eco-friendly, in-situ, and one-step synthesis of ZnO-Co3O4 core-shell heterostructure (ZC-CSH) using the hydrothermal process as a transcendent nanomaterial for the supercapacitor applications. The ZC-CSH SSC showed a wide potential window (1.6 V), the excellent specific capacitance of 177.0F g−1 at 1.4 A g−1, high energy density (39.3 W h kg−1), and power density (19064.3 W kg−1). Further, the ZC-CSH SSC revealed excellent stability of 92.8 % after 10,000 cycles at 12.4 A g−1 using galvanostatic charging-discharging. Besides, the ZC-CSH SSC unraveled the outstanding stability of 96.1 % after the 8 h Voltage holding tests (VHT) at 1.6 V + 8 h Self-discharge tests (SDT). Moreover, the ZC-CSH SSC indicated a trivial leakage current of 0.06, 0.11, 0.15, and 0.17 mA during 2, 4, 6, and 8 h VHT, respectively. The ZC-CSH SSC demonstrated a voltage drop from 1.6 V to 0.39, 0.38, 0.37, and 0.36 V after 2, 4, 6, and 8 h VHT and SDT. To understand the ZC-CSH SSC's self-discharge behavior, this work explored the insights of the self-discharge mechanisms based on two thermodynamic processes, ionic concentration gradient (diffusion-control model) and potential difference (potential-driven model). Also, according to the tight-bonding (strong interactions) and loose-bonding (weak interactions), this work envisaged electrolyte ions' interactions with electrode materials to explore the coherent insights of the self-discharge behavior of the ZC-CSH SSC. It is concluded that this approach can lead to an unwavering performance of the ZC-CSH SSC for electronic portable futuristic gadgets. © 2021 Elsevier B.V.