Kothandaraman Ramanujam

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.

A DSSC with an Efficiency of ∼10 %: Fermi Level Manipulation Impacting the Electron Transport at the Photoelectrode‐Electrolyte Interface

Abstract: In the literature, many studies pertain to gold (Au) nanoparticles, (NPs) incorporated dye-sensitized solar cells (DSSCs) were reported due to the beneficial effect of the surface plasmon polaritons originating from the Au NPs on the DSSC performance. Thiolated Au quantum dots and dye based DSSCs was explored recently, wherein the Au cluster act both as sensitizer and voltage booster by enhancing the quasi-Fermi level of TiO2. There is a knowledge gap on effect of thiolated Au NPs on DSSC performance. In this study, we have demonstrated Fermi level equilibration between the TiO2 and thiolated Au NPs. Thiolated Au NPs blocks the back electron transfer at the thiolated Au NPs-electrolyte interface thereby improving the open circuit voltage and efficiency of DSSCs. We have also shown beneficial effect of WO3–TiO2–thiolated Au NPs interface in enhancing the DSSC performance significantly in comparison to that of sole TiO2 based DSSC. For the DSSC cell: FTO/WO3/TiO2-Au-thiolated/N719, an efficiency of 9.9 % is achieved (JSC = 17.4 mA cm−2, VOC = 0.820 V and FF=0.70).

Carbon-supported Co(III) dimer for oxygen reduction reaction in alkaline medium

Abstract: Non-precious metal electrocatalysts obtained by pyrolysis of precursors of metal, nitrogen, and carbon (MNC) are viewed as an inexpensive replacement for platinum-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. The hypothesized ORR active site structure of typical MNC catalysts consists of a transition metal coordinated to the pyridinic/pyrollic type of nitrogen covalently attached to the edges of the graphitic crystallites. One of the drawbacks of all the reported procedures to synthesize these MNC electrocatalysts is the inability to control the formation of a specific active site structure suitable for ORR. Lack of clarity on the active site structure limits the researcher’s ability to design a synthesis methodology that maximizes the specific active site density. In this study, we have synthesized a Co(III) dimer ([Co2(OH)2(OOCCH3)3(bpy)2] NO3 ⋅ 1.5 H2 O) and demonstrated its ORR activity in alkaline medium. The ORR activity and methanol tolerance property of the Co(III) dimer were compared with those of Ketjenblack carbon (used as support for Co(III) dimer) and commercial 20 wt% Pt/C, respectively. Since Co(III) dimer is a molecular material, its characterization by single-crystal X-ray diffraction, nuclear magnetic resonance, and infrared studies revealed the chemical structure unambiguously. Density functional theory calculation predicted the possibility of both end-on and side-on oxygen adsorption at the metal center of the Co(III) dimer.

New cyclic and acyclic imidazole-based sensitizers for achieving highly efficient photoanodes for dye-sensitized solar cells by a potential-assisted method

Abstract: A series of systematically tailored aryl acyclic (biphenyl, dye 1 and 2), cyclic (phenanthrene, dye 3 and 4) and methyl-substituted (dye 5) imidazole derivatives were synthesized and characterized for application in dye-sensitized solar cells (DSSCs). The anisole ancillary donor was attached to the –NH position in the imidazole center to obtain dyes 2 and 4. Cyclic voltammetry and UV-visible studies of all the dyes indicate their suitability for DSSC applications. Among the as-synthesized dyes, dye 4 with a phenanthrene donor and anisole ancillary donor showed the highest power conversion efficiency (PCE) of 7.16% (JSC = 13.07 mA cm−2, VOC = 0.831 V, FF = 0.659). Dye 2 displayed the highest electron lifetime in the conduction band of the photoanode; hence, the open circuit voltage of the DSSC based on dye 2 was the highest among the studied dyes (0.865 V). By using a novel potential-assisted dye staining process, the dye loading on the photoanode was enhanced by 18% in 1 h, which in turn enhanced the PCE to 8.10%.

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

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.

Metal–Organic Frameworks in Heterogeneous Catalysis: Recent Progress, New Trends, and Future Perspectives

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...

Molecularly Imprinted Polymers

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...

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

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

Durability Investigation of Carbon Nanotube as Catalyst Support for Proton Exchange Membrane Fuel Cell Electrode

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.