Browsing by Author "Vikram Rathour"

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A Co and Fe bimetallic MOF with enhanced electrocatalytic oxygen evolution performance: exploring the electronic environment modifications upon Fe incorporation
(Royal Society of Chemistry, 2024) Varsha Singh; Devesh Kumar Singh; Mamta Yadav; Smita Singh; Vikram Rathour; Ananya Tiwari; Vellaichamy Ganesan
The incorporation of iron into the cobalt-based metal-organic framework (Co-MOF) modifies the electronic environment and the resulting bimetallic MOF exhibits enhanced oxygen evolution reaction (OER) performance. The Co-MOF, Fe-MOF, and different ratios of bimetallic Co-Fe-MOFs are prepared using 2,2′-bipyridine 4,4′-dicarboxylic acid (H2bpdc) by a single-step hydrothermal process. The MOFs are evaluated by necessary spectroscopy and microscopy techniques like Fourier transform infrared spectroscopy, inductively coupled plasma emission spectroscopy, powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The incorporation of Fe3+ into the Co-MOF significantly increases the electrocatalytic activity of the resulting bimetallic Co-Fe-MOF towards the OER. An optimized bimetallic MOF having a Co : Fe ratio of 2 : 1 shows the lowest overpotential (310 mV) to realize the 10 mA cm−2 current density and the lowest Tafel slope of 53 mV dec−1 with excellent durability in comparison to the Co-MOF, the Fe-MOF, and the state-of-the-art catalyst, RuO2. Furthermore, this manuscript addresses the inherent electrocatalytic properties of MOF-based electrocatalysts and demonstrates their possible exploitation in water electrolysis. © 2024 RSC.
Carbon-Based Nanomaterials and Their Green Energy Applications: Carbon Nanotubes
(wiley, 2024) Smita Singh; Varsha Singh; Vikram Rathour; Vellaichamy Ganesan
In today’s world, the rapid exhaustion of non-renewable energy sources has led to a significant surge in renewable and green energy alternatives. Electrochemical devices are considered to be one of the reliable alternatives. Carbon-based nanostructures, including graphene, carbon nanotubes (CNTs), and similar materials have drawn substantial interest owing to their distinct physicochemical and electrical properties, which render them promising candidates for green energy applications. With the first finding of CNTs by Iijima in 1991, they are exploited in many fields. CNTs are the one-dimensional allotrope of carbon, possessing long hollow tube-like structures made up of sp2carbon having a diameter of nanoscale range and length in micrometers. On the basis of the number of tubes in their structure, they can be either single-or multi-walled CNTs (SWCNTs and MWCNTs, respectively). They have grabbed the interest of researchers owing to their unique chemical composition and many alluring properties like high conductivity, huge mechanical strength, and large surface area. Numerous carbon-based nanomaterials exhibit fascinating structure-property relationships, but it is the CNTs that have garnered the most intense research focus. Owing to such unique properties, CNTs have been utilized either directly as the electrode material or as a support in almost all the fields of electrochemistry: be it sensing, energy conversion, or energy storage applications. CNTs have demonstrated promising results in enhancing the proficiency of energy conversion and storage strategies, thereby contributing to the advancement of green energy innovations. In this chapter, the synthesis, characterization, and unique properties of CNTs are delved. Moreover, its vital role in various green energy applications, specifically in the areas of oxygen electrocatalysis and supercapacitors, is comprehensively discussed. © 2025 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.
Hollow core mesoporous carbon spheres as catalyst support for improved platinum utilization in phosphoric acid fuel cells
(Elsevier B.V., 2024) Vaibhav Verma; Suhasini Roy Choudhury; Vikram Rathour; Suman Roy Choudhury; Vellaichamy Ganesan
Using a well-known sol-gel technique, monodispersed silica spheres measuring 380 nm in size are generated in situ. These silica spheres serve as a template for the synthesis of hollow core mesoporous shell (HCMS) carbon spheres. Inside the pores of the template, a polymer is synthesized using azoisobutyronitrile and divinylbenzene polymerization route. Polymer carbonization followed by template remotion yielded HCMS carbon spheres. This HCMS carbon is mesoporous and offers uniform Pt crystallite distribution for acid fuel cell applications. As-prepared HCMS carbon is examined by field emission gun SEM, TEM, nitrogen adsorption/desorption isotherm (BET surface area and BJH pore size distribution analysis), and apparent density using Helium pycnometry. The HCMS carbon obtained demonstrates a BET surface area of 623 m2g-1, showcasing a uniform pore size distribution centered at 3.8 nm. This specific characteristic renders it an ideal support material for fuel cell catalysts. The electrochemical studies reveal the key parameters like corrosion resistance, bulk electrical conductivity, the electrochemical surface area of Pt chemically deposited on HCMS carbon, and unit fuel cell performance under phosphoric acid environment. These parameters are compared with the standard carbon powder, Vulcan XC72R and a commercial catalyst to evaluate the HCMS carbons’ suitability for fuel cell applications. © 2024 Elsevier Inc.
Iron phthalocyanine integrated with boron-doped reduced graphene oxide for highly selective four-electron oxygen reduction: an experimental study
(Royal Society of Chemistry, 2024) Vikram Rathour; Smita Singh; Varsha Singh; Devesh Kumar Singh; Mamta Yadav; Ananya Tiwari; Vellaichamy Ganesan
Iron phthalocyanine (FePc) has been integrated on boron-doped reduced graphene oxide (B-RGO) resulting in the composite, FePc@B-RGO. Boron alters the electronic structure around FePc and shows a higher selectivity than that of the benchmark catalyst, Pt/C, for four-electron oxygen reduction. FePc@B-RGO exhibits high oxygen reduction reaction activity with a high onset potential and half-wave potential (0.95 and 0.85 V vs. RHE respectively). FePc@B-RGO also shows a low Tafel slope of 39 mV dec−1 and high efficiency, stability, and methanol crossover for oxygen reduction in basic media. © 2024 RSC
NaCl-templated synthesis of soybean-derived nitrogen-rich mesoporous carbon material: iron phthalocyanine integration for four-electron oxygen reduction
(Royal Society of Chemistry, 2024) Vikram Rathour; Smita Singh; Varsha Singh; Devesh Kumar Singh; Vaibhav Verma; Piyush Kumar Sonkar; Vellaichamy Ganesan
The performance efficiency of fuel cells and metal-air batteries mainly depends on the cathodic oxygen reduction reaction (ORR). In this work, soybean-derived mesoporous carbon is synthesized by the carbonization of soybean powder using an inexpensive template, NaCl which creates porosity as well as limits the vaporization of heteroatoms by generating a protective layer. Soybean powder carbonized at 950 °C (SN950) shows high catalytic activity towards ORR in basic medium. To further enhance the ORR activity, iron phthalocyanine (FePc) was immobilized on the soybean-derived carbon and the resulting material is represented as FePc@SN950. FePc@SN950 and other control samples were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller analysis, and X-ray photoelectron spectroscopy techniques. FePc@SN950 shows an onset potential (Eonset) of 0.97 and 0.77 V (vs. RHE) and half-wave potential (E1/2) of 0.92 and 0.70 V (vs. RHE) in basic and acidic media, respectively. Selectivity and percentage formation of H2O2 of the materials are measured by hydrodynamic experiments. The number of electrons transferred is found to be 3.5 and 3.8 in basic and acidic media, respectively. The selectivity for the formation of water was evaluated as 80% and 94% respectively in the basic and acidic media throughout the ORR region. The stability and durability of the material are checked by amperometry and cyclic voltammetry (CV) methods, where there are no significant changes in the current and Eonset values after 10 000 s and 3000 CV cycles respectively, in both acidic and basic media. Therefore, it is demonstrated that the synthesized SN950 has a large potential to replace conventional catalytic supports (like graphene, carbon nanotubes, and carbon fiber). FePc@SN950 could be used as a potential candidate to replace Pt-based catalysts in fuel cells and metal-air batteries. © 2024 The Royal Society of Chemistry.
Phenosafranine integrated sulfonic acid-functionalized multi-walled carbon nanotubes for Cr(VI) detection
(Elsevier Ltd, 2024) Ananya Tiwari; Mamta Yadav; Smita Singh; Varsha Singh; Vikram Rathour; Vellaichamy Ganesan
This work presents the electroanalytical detection of hexavalent chromium, Cr(VI) using glassy carbon electrode modified with phenosafranine (PS+) ion exchanged on sulfonic acid-functionalized multi-walled carbon nanotubes (MWCNT-SO3H) i.e., MWCNT-SO3--PS+ as an electrochemical sensing platform (ESP). The prepared material, MWCNT-SO3--PS+ is assessed using various physiochemical characterization techniques for the successful ion exchange of PS+ onto the MWCNT-SO3H. The electrochemical viability of PS + for the electrocatalysis at the prepared ESP is tested using cyclic voltammetry. The ESP shows high sensitivity and selectivity towards Cr(VI) determination in the presence of several possible interferences with a limit of detection of 0.36 μM. Water samples from two sources are utilized for the real sample analyses showing a high recovery percentage with acceptable average relative standard deviation values. The proposed ESP exhibits high operational stability and storage stability with negligible change in current for more than a month. © 2024 Elsevier B.V.
Unveiling Enhanced Oxygen Reduction in Multi-Walled Carbon Nanotube-Supported MnCo2O4: Experimental and Theoretical Insights into Tin Substitution for Octahedral Cobalt
(American Chemical Society, 2024) Smita Singh; Anshu Shrivastava; Varsha Singh; Vikram Rathour; Indrajit Sinha; Vellaichamy Ganesan
In this work, Sn-doped manganese cobaltite (Snx-MnCo2O4) was synthesized by using a solvothermal method followed by an annealing process. To further increase its catalytic efficiency, it was integrated onto a carbon support, carboxylic acid-functionalized multiwalled carbon nanotubes (fMWCNTs). Among the synthesized materials, fMWCNT-supported Sn-doped MnCo2O4 exhibits the highest onset potential for oxygen reduction and shows a distinctly selective four-electron oxygen reduction, as demonstrated by the rotating disc electrode and rotating ring disc electrode experiments. X-ray photoelectron spectroscopy reveals a shift in the binding energy of Mn 2p owing to alterations in the electronic structure of the crystal upon incorporation of Sn into MnCo2O4. Computational studies proved the replacement of octahedral Co ions in the MnCo2O4 crystal structure by Sn4+ ions. The withdrawal of electron density by Sn4+ species from the active centers (Mn3+) leads to an increased electropositive character at the Mn3+ centers. Since Mn3+ centers are the effective active centers in this catalyst, oxygen is efficiently adsorbed at these active centers, resulting in enhanced electrocatalytic activity. © 2024 American Chemical Society.
ZnMn2O4 spinel nanocrystals-decorated multi-walled carbon nanotubes for oxygen reduction: Experimental and theoretical studies on the strong coupling facilitated four-electron selectivity
(Elsevier Ltd, 2024) Smita Singh; Anshu Shrivastava; Devesh Kumar Singh; Mamta Yadav; Varsha Singh; Vikram Rathour; Ananya Tiwari; Indrajit Sinha; Vellaichamy Ganesan
In this work, we have successfully formulated a single-step hydrothermal synthesis of mixed transition metal oxide nanocrystals (ZnMn2O4) strongly coupled on carbon support (MWCNTs) that acts as an efficient electrocatalyst for the electrochemical oxygen reduction reaction (ORR). The results depict that the composite, MWCNTs@ZnMn2O4 shows better electrocatalytic activity as compared to the activity exhibited by its individual components MWCNTs and ZnMn2O4 combined, attributed to the strong coupling between the two components. Transmission electron images of the composite depict that ZnMn2O4 nanocrystals have been successfully integrated on MWCNTs resulting in high conductivity and activity. The composite, MWCNTs@ZnMn2O4 exhibits an onset potential of 0.9 V vs. RHE, 99 % four-electron ORR selectivity, and high stability. The high selectivity and stability are assigned due to the strong coupling of ZnMn2O4 to MWCNTs through Zn/Mn–O–C bonds which are proved from DFT studies. The presence of Zn/Mn–O–C bonds is verified from X-ray photoelectron spectroscopy. © 2023 Hydrogen Energy Publications LLC
π-Extended nonplanar cobalt porphyrins immobilized on MWCNTs as efficient electrocatalysts for selective oxygen reduction reaction
(Royal Society of Chemistry, 2024) Amir Sohel Bulbul; Vikram Rathour; Vellaichamy Ganesan; Muniappan Sankar
Two π-extended cobalt porphyrins are synthesized and one of them is crystallographically characterized. The nanocomposites of nonplanar (curved) porphyrin immobilized multi-walled carbon nanotubes were thoroughly characterized spectroscopically and microscopically, showing ∼200 mV positive shift in the O2 reduction peak potential in aqueous media and ∼100 mV shift in the onset potential of the O2 reduction relative to the control meso-tetraphenylporphyrinatocobalt(ii) nanocomposite. Both the π-extended cobalt porphyrin immobilized nanocomposites efficiently catalyze selective 4e−/4H+ O2 reduction under ambient conditions with excellent methanol tolerance and high stability due to effective π-π interactions, and could be an alternative for expensive Pt-based cathode materials in fuel cells. © 2024 The Royal Society of Chemistry.