Browsing by Author "Amit Kumar Verma"

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Correction: Enhanced activity and chlorine protection in prolonged seawater electrolysis using MoS2/sulfonated reduced graphene oxide (Sustainable Energy and Fuels (2025) 9 (4300-4319) DOI: 10.1039/D5SE00541H)
(Royal Society of Chemistry, 2025) Prerna Tripathi; Renna Shakir; Amit Kumar Verma; Jeyakumar Karthikeyan; Biswajit Ray; Akhoury Sudhir Kumar Sinha; Shikha K. Singh
The authors regret that the details of the affiliations were not correct in the original manuscript. The corrected affiliations for this paper are as shown herein. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © 2025 The Royal Society of Chemistry.
Enhanced activity and chlorine protection in prolonged seawater electrolysis using MoS2/sulfonated reduced graphene oxide
(Royal Society of Chemistry, 2025) Prerna Tripathi; Renna Shakir; Amit Kumar Verma; Jeyakumar Karthikeyan; Biswajit Ray; Akhoury Sudhir Kumar Sinha; Shikha K. Singh
Electrolyzer technology necessitates the use of seawater instead of freshwater to achieve a comprehensive supply of clean and economical energy. However, the tendency of chloride ions (Cl−) to significantly erode the metal surface is a major challenge during seawater electrolysis. Therefore, designing an electrode that is resistant to chloride ions is of great importance to develop an efficient seawater electrolyser. In this work, we present a double layer anode consisting of a molybdenum sulfide electrocatalyst uniformly deposited over sulfonated graphene sheets coated over an Ni foam. The developed electrode (GNiMoOS) helps selectively convert H2O into H2 and O2 rather than chloride (Cl−) ions into ClO− in a seawater environment by resisting corrosion due to the Cl− ions in seawater. The chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) provides solid evidence that the GNiMoOS electrocatalyst blocks the chloride oxidation reaction owing to its distinct resistance to Cl−. In addition, density functional theory (DFT) calculations clearly validated the preference of sulfonic moieties towards OH− compared with Cl− ions, confirming the chlorine repelling properties of the GNiMoOS electrode. The successful in situ functionalisation of sulfonic moieties into the reduced graphene oxide (RGO) skeleton with simultaneous development of flower-like MoS2 was well confirmed using XPS, Raman, SEM, TEM, and FT-IR techniques. GNiMoOS delivered an impressive current density of 100 mA cm−2 for OER and HER at room temperature, requiring remarkably low overpotentials of just 180 mV and 201 mV, respectively. Industrial faradaic current densities (400-600 mA cm−2) were reported with the active electrode at combined overpotentials of ≤600 mV at room temperature. The unique morphology of MoS2 provides more active sites for the HER/OER, while sulfonated functional groups over graphene impart much-needed anticorrosion properties to the system. Moreover, the electrical coupling between MoS2 and RGO can make the electron transfer to RGO easier. Therefore, the synergistic interactions among MoS2, SO3H and RGO lead to improved catalytic activity and prolonged stability. © 2025 The Royal Society of Chemistry.
Fabrication and evaluation of a self-standing reduced graphene-tungsten oxides hybrid electrode for acidic water splitting
(Elsevier Ltd, 2022) Prerna Tripathi; Amit Kumar Verma; Anju Vishwakarma; Kheyanath Mitra; Biswajit Ray; A.S.K. Sinha; Shikha Singh
Efficient and sustained hydrogen production via acidic water splitting is of great importance in the electrolyzer industry. Here, we have designed and synthesized a self-assembled, freestanding, three dimensional (3D) reduced graphene-non-noble tungsten oxide (SA-GWO) electrode with high comprehensive acidic electrolysis performance. Adsorption isotherm suggested the formation of mesoporous structural design within a 3D self-assembled SA-GWO architecture electrode. Bi-functional (HER and OER) activity has been displayed by SA-GWO electrodes at the combined full potential of 1.9 V and attains the standard 10 mA/cm2 (1 M H2SO4, 28 °C). Remarkably, it exhibits OER activity in the acidic medium, which is so far very limited. The tafel slope and the exchange current density for the HER process are observed to be 117 mV/decade and 1.73 × 10−3 mA/cm2, respectively, at 28 °C. Importantly, the production rate of hydrogen is found to increase with increasing temperature. HER is highly dominated by the Volmer route. Gas liberated at the respective electrode has been tested via gas chromatography (GC) analysis. SA-GWO supports the faradaic efficiency of 73 and 52% for HER and OER, respectively. Tafel slope for OER appeared to be very high owing to its complex mechanistic pathway. Disintegration of 3D monoclinic WO3 and the formation of 2D nanochannels like nanostructure have been distinctly observed in SEM micro images, when the electrode is subjected to cathodic HER reaction (−0.5 V, 1 M H2SO4). Most importantly, the WO3 polymorph typically responsible for the distinct mechanism of HER and OER action in 1 M H2SO4 has been identified and proven. Moreover, the 3D SA-GWO electrode as HER possesses great endurance and incomparable stability in acidic media. © 2022 Hydrogen Energy Publications LLC
Photocatalytic Production of Oxygen by Nitrogen Doped Graphene Oxide Nanospheres: Synthesized via Bottom-Up Approach Using Dibenzopyrrole
(John Wiley and Sons Inc, 2022) Amit Kumar Verma; Prerna Tripathi; Zahoor Alam; Shiva Kant Mishra; Biswajit Ray; A.S.K. Sinha; Shikha Singh
In this article, we present the formation of nitrogen (N) doped graphene oxide nanospheres (N-GONs) and investigate their applicability for photocatalytic water splitting. We chose a simple “bottom-up” method for synthesizing N-GONs. Dibenzopyrrole as a basic structural unit was used for constructing N-GONs. Nitration is an intermediate step, subsequent hydrothermal treatment of nitro derivatives imparted oxygen functionalities, which was well proved via CHNS and XPS analysis. ∼14 % and 39 % of nitrogen and oxygen were present inside N-GONs. The average size of N-GONs is in-between 30–80 nm. N-GONs typically have a band gap of nearly 2.61 eV. The valance and the conduction bands alignments of N-GONs w.r.t to standard hydrogen electrode were evaluated through UPS and XPS studies. The alignments were found to be well suited for H2O splitting applications. N-GONs have n-type semiconductor features and a charge carrier density of 1.12×1022 cm−3. While studying photocatalytic dissociation of water we identified oxygen as the only product. Significantly, 1 g of N-GONs produced ∼1.3 mmol of oxygen over the course of 1 h. These backgrounds clearly suggest the possibilities of ongoing oxygen reduction and oxygen evolution reactions simultaneously. No-significant traces of H2O2 were observed which suggested immediate H2O2 disproportionation to O2 and H2O on N-GONs. The proposed photocatalytic activity of N-GONs is also confirmed by RRDE method for ORR catalysis. © 2022 Wiley-VCH GmbH.
Signal generation in MIP sensors
(Elsevier, 2023) Piyush Kumar Sonkar; Amit Jaiswal; Ranjeet Kumar; Angesh Kumar Maurya; Narvadeshwar; Amit Kumar Verma
Signal generation from the sensors is based on three compartments: a reactor, a transducer, and a detector. Transducers mediate the signals generated from the reactor to detectors. It plays a crucial role in sensing devices. The use of molecularly imprinted polymers (MIPs) in sensor development is increasing due to their high selectivity and sensitivity. The most difficult aspect is creating MIP sensors with the right transducers to provide measurable signals. The fundamentals of signal creation, their improvement to reduce noise levels, and other challenges associated with signals when converting to detectors will all be covered in this chapter. This chapter's conclusion will also maintain a futuristic perspective. © 2023 Elsevier Inc. All rights reserved.
Thermally tunable dual channel toroidal metasurface on VO2 platform
(American Institute of Physics, 2025) S. N. Yogitha; Nityananda Acharyya; Abhishek Mishra; Akkanaboina Mangababu; Amit Kumar Verma; Dhanvir Singh Rana; Dibakar Roy Chowdhury
Active modulation of electromagnetic response in terahertz (THz) regime has gathered plenty of attention owing to its multifunctional applications. In this regard, metasurfaces integrated with VO2 as active material can create compelling pathways for actively controlling terahertz propagation. Hence, we have demonstrated a design of dual toroidal active metasurface by realizing plasmonic split-ring resonators on the VO2 thin film for dynamic and real-time control over THz wave propagation. These metasurfaces exhibit agile modulation of multiple resonances by exploiting insulator-to-metal transition (IMT) phenomena exhibited by VO2. For this purpose, sample temperature is varied from 26 to 110 °C. It is observed that at 110 °C, VO2 conductivity increased significantly resulting in a 46% peak amplitude modulation with respect to room temperature. Besides temperature induced tunability mediated by VO2 activated IMT, these metasurfaces manifest temperature tunable electric, magnetic, and toroidal modes which is further validated by rigorous multipole analysis. Hence, these outcomes provide a framework for implementing VO2 based temperature tunable THz metadevices for futuristic applications such as thermal sensors, modulators, terahertz switching, tunable absorbers, and photonic memory. © 2025 Author(s).