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Author

Kothandaraman Ramanujam

Other affiliations: Michigan State University
Bio: Kothandaraman Ramanujam is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Catalysis & Chemistry. The author has an hindex of 12, co-authored 67 publications receiving 544 citations. Previous affiliations of Kothandaraman Ramanujam include Michigan State University.

Papers published on a yearly basis

Papers
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Journal ArticleDOI
TL;DR: In this article, six new dyes based on phenothiazine conjugated to an ethynyl-pyrene moiety were synthesized and characterized, and they were fabricated using these dyes with and without a co-adsorbent, chenodeoxychloicacid.
Abstract: Six new dyes based on phenothiazine conjugated to an ethynyl-pyrene moiety are synthesized and characterized. Dye-sensitized solar cells are fabricated using these dyes with and without a co-adsorbent, chenodeoxychloicacid. Simple molecular engineering around the phenothiazine moiety enabled a maximum of 12% photoconversion efficiency with one of the dyes.

96 citations

Patent
21 Aug 2009
TL;DR: In this paper, a carbon-metal-nitrogen oxygen reducing cathode catalyst is proposed, which consists of mixing a carbon source with a transition metal precursor to form a metal precursor loaded carbon substrate, adding a nitrogen precursor compound to the metal precursor and pyrolyzing it in a closed vessel.
Abstract: A method for making a carbon-metal-nitrogen oxygen reducing cathode catalyst, the method comprising mixing a carbon source with a transition metal precursor to form a metal precursor loaded carbon substrate; adding a nitrogen precursor compound to the metal precursor loaded carbon substrate to form a carbon-metal-nitrogen precursor; and pyrolyzing the carbon-metal-nitrogen precursor in a closed vessel, thereby forming an oxygen reducing cathode catalyst. The carbon-metal-nitrogen catalyst requires no precious metal such as Pt, and also provides benefits such as controlled deposition of catalytically active nitrogenous compounds that can increase the catalytic activity of the catalyst when compared to gaseous deposition of nitrogen to the surface of the carbon support.

45 citations

Journal ArticleDOI
TL;DR: In this article, the authors used activated porous carbon (ACTS-900) derived from Tamarindus indica, a bio-source, via KOH activation and carbonization at 900°C was used as an active electrode material for supercapacitor (SC) applications.
Abstract: Herein, activated porous carbon (ACTS-900) derived from Tamarindus indica, a bio-source, via KOH activation and carbonization at 900 °C was used as an active electrode material for supercapacitor (SC) applications. In the three-electrode configuration, ACTS-900 shows the maximum specific capacitance (Cs,3E) of 225 F g−1 at 50 mV s−1 and 249 F g−1 at 0.5 A g−1 in 1 M H2SO4. A high-performance, bio-based, environmentally benign and cost-effective chitosan/poly(ethylene glycol)-ran-poly(propylene glycol) [Ch/poly(EG-ran-PG)]-based polymer blend was employed as a membrane-cum-separator as well as a green binder in the electrodes. The blend polymer membrane was prepared by mixing chitosan (Ch) and poly(EG-ran-PG) in a 1 : 1 weight ratio in a 1% aqueous acetic acid solution followed by drying under controlled evaporation. The blend membrane showed high porosity (2 μm–7 μm diameter pores) and excellent thermal (up to 250 °C), chemical (in 1 M H2SO4), electrochemical (up to 1.21 V) and mechanical stability (up to 39 MPa under tensile loading). The performance of a symmetric two-electrode SC device was evaluated using a H2SO4-(1 M)-soaked-Ch/poly(EG-ran-PG) membrane and ACTS-900 active electrode materials. The obtained results were compared with those obtained using commercially available binders and membranes. The single electrode specific capacitances (Cs,2E) in the symmetrical SC device were 193 F g−1 at 50 mV s−1 and 132 F g−1 at 2 A g−1 with H2SO4-(1 M)-soaked-Ch/poly(EG-ran-PG) as the membrane and binder. The maximum energy density and power density of the SC device are 4.7 W h kg−1 (at 1 A g−1) and 2.5 kW kg−1 (at 5 A g−1), respectively. Due to the superior wetting properties of the blend membrane and binder, excellent capacity retention was observed (∼99%) over 6000 cycles at the current density of 3.5 A g−1. As a proof-of-concept, a red light-emitting diode was illuminated using three serially connected 3 V SC stacks.

31 citations

Journal ArticleDOI
04 Apr 2018
TL;DR: A new semiconductive and low-optical band gap CP structure, 1, is reported, that exhibits high-performance ORR in alkaline medium and can be used as a promising cathode material for fuel cells in terms of efficiency and cost effectiveness.
Abstract: Lack of control over the structure and electrically nonconductive properties of coordination polymers (CPs) creates a major hindrance to designing an active electrocatalyst for oxygen reduction reaction (ORR). Here, we report a new semiconductive and low-optical band gap CP structure [{Co3(μ3-OH)(BTB)2(BPE)2}{Co0.5N(C5H5)}], 1, that exhibits high-performance ORR in alkaline medium. The electrical conductivity of compound 1 was measured using impedance spectroscopy and found to be 5 × 10–4 S cm–1. The Ketjenblack EC-600JD carbon used as a support for all the electrochemical methods such as cyclic voltammetry, rotating disk electrode, rotating ring-disk electrode and Koutecký–Levich analysis. The as-synthesized Co-based catalyst has the ability to reduce O2 to H2O by a nearly four-electron process. The crystal structure of 1 shows that the trimeric unit {Co3(μ3-OH)(COO)5N3} and monomeric unit {Co(COO)2(NC5H4)2}2+ are linked with BTB and BPE linkers to form a three-dimensional structure. Theoretical calculat...

27 citations

Journal ArticleDOI
TL;DR: In this paper, selenium was used as a ligand to replace the nitrogen coordinated to the iron atom in the electrocatalyst, thereby imparting control on the nitrogen content.
Abstract: Non-precious metal electrocatalysts based on pyrolysed metal-nitrogen-carbon (MNC) are viewed as an inexpensive replacement for platinum-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. One of the drawbacks of all the reported procedures to synthesize MNC electrocatalysts is the inability to control the nitrogen content. Since the type of nitrogen present (pyridinic, pyrrolic, quaternary/graphitic) and their proportions both play a seminal role in deciding the ORR activity of the electrocatalyst, it is important to carefully study the effect of nitrogen content on electrocatalyst properties. In this study, selenium was used as a ligand to replace the nitrogen coordinated to the iron atom in the electrocatalyst, thereby imparting control on the nitrogencontent.Uponintroducing14at%ofselenium,theNcontentofthecatalystdroppedto3.7wt%andtheORRactivityreached a maximum of 7.2 mA cm −2 at 0.8 V vs. RHE. We demonstrated the need for iron to complete the active site: upon complexing the iron site with bipyridine, ethylene diammine and oxalic acid in 1N H2SO4, the overpotential toward the ORR increased by ∼60 mV, ∼140 mV and ∼140 mV respectively at 2 mA cm −2 .

26 citations


Cited by
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Journal ArticleDOI
TL;DR: This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core-shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts and metal-free catalysts.
Abstract: The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

2,964 citations

Journal ArticleDOI
TL;DR: In this review, the recent advances in the application of MOFs in heterogeneous catalysis are discussed and the personal view on future research directions is wrapped up.
Abstract: More than 95% (in volume) of all of today’s chemical products are manufactured through catalytic processes, making research into more efficient catalytic materials a thrilling and very dynamic rese...

772 citations

Journal ArticleDOI
TL;DR: This review describes the imprinted polymer production processes, the techniques used for reporting, and the applications of the reported sensors, including those designed to detect toxic chemicals, toxins in foods, drugs, explosives, and pathogens.
Abstract: Molecularly imprinted polymers are synthetic receptors for a targeted molecule. As such, they are analogues of the natural antibody–antigen systems. In this review, after a recounting of the early history of the general field, we specifically focus on the application of these polymers as sensors. In these applications, the polymers are paired with a reporting system, which may be electrical, electrochemical, optical, or gravimetric. The presence of the targeted molecule effects a change in the reporting agent, and a calibrated quantity of the target is recorded. In this review, we describe the imprinted polymer production processes, the techniques used for reporting, and the applications of the reported sensors. A brief survey of recent applications to gas-phase sensing is included, but the focus is primarily on the development of sensors for targets in solution. Included among the applications are those designed to detect toxic chemicals, toxins in foods, drugs, explosives, and pathogens. The application...

749 citations

Journal ArticleDOI
TL;DR: A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal catalysts is presented and suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided.
Abstract: A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed Additionally, the recent application of Cu-based catalysts for the ORR is reviewed Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided

591 citations

17 Feb 2006
TL;DR: In this paper, the authors compared the performance of carbon nanotubes (MWNTs) and Vulcan XC-72 in terms of surface oxide formation and 30% lower corrosion current.
Abstract: Abstract Electrochemical surface oxidation of carbon black Vulcan XC-72 and multiwalled carbon nanotube (MWNT) has been compared following potentiostatic treatments up to 168 h under condition simulating PEMFC cathode environment (60 °C, N2 purged 0.5 M H2SO4, and a constant potential of 0.9 V). The subsequent electrochemical characterization at different treatment time intervals suggests that MWNT is electrochemically more stable than Vulcan XC-72 with less surface oxide formation and 30% lower corrosion current under the investigated condition. As a result of high corrosion resistance, MWNT shows lower loss of Pt surface area and oxygen reduction reaction activity when used as fuel cell catalyst support.

536 citations