Raghuram Chetty

Fuel Cell Hybrid Electric Vehicles (FCHEVs) have the potential for providing a solution for clean transportation. For FCHEVs to be successful, it is important to improve their fuel economy and acceleration performance. One of the important systems to be worked on to achieve these goals is the vehicle's powertrain. This research work aims at providing a systematic procedure for multi-objective optimum sizing of a FCHEV powertrain, with the objectives of minimizing the fuel consumption and maximizing the acceleration performance. The work was carried out for a fuel cell-battery hybrid heavy road vehicle for Indian driving cycle. The design variables in the component sizing process were chosen to be speed ratio (x) of the traction motor and degree of hybridization (H) of the power sources. The values of objective functions and constraints were evaluated using ADVISOR software for a sample set of design variables. Surrogate modelling technique was adopted for constructing models for objective functions and constraints. Then, the optimization was carried out using multi-objective genetic algorithm approach to find the Pareto optimal solutions for the problem. This study provides a framework for component sizing of FCHEV that considers x and H as design variables.

In this article, Box–Behnken experimental design methodology was successfully used to consider the effects of silver (Ag)ion concentration and temperature of reaction together with the interaction between Ag+ and reducing agent (hydrazine)concentration on the yield of Ag nano-rods. The statistical and variance analysis was presented, which indicated the factors with higher influence over the model response. By applying such model, the optimum conditions for effective factors were determined for obtaining Ag nano-rods with yield per volume 0.6–0.7, which was at Ag+ concentration of 0.19 g/ml, molar ratio between surfactants of 1, concentration of hydrazine of 0.5 g/ml and nano-rods formation temperature of 90 °C, and was found to give 0.55 g/ml varied from predicted values which was 0.7g/ml with Ag nano-rod outer diameter of 59–73 nm.

Palladium (Pd) dendrites on carbon black support were synthesized by a simple template/surfactant-free electrochemical deposition. In comparison to Pd spherical deposit obtained on non-activated carbon, Pd deposited on an electrochemically activated carbon displayed a dendritic morphology with increased electrochemical surface area and showed enhanced catalytic activity for formic acid oxidation. The effect of electrochemical activation and deposition cycles were studied in relation to the growth and morphological features of Pd deposit. Scanning electron micrographs and X-ray diffraction studies showed a transition in Pd morphology from spheres to dendrites when the carbon support was subjected to varying cycles of electrochemical activation, prior to Pd deposition. Raman and X-ray photoelectron spectra results showed that the defects induced during electrochemical activation on carbon played a major role in tailoring the Pd morphology.

Palladium (Pd) dendrites were synthesized on electrochemically activated carbon (Vulcan XC-72R) support by a simple template free potentiostatic (constant voltage) deposition. Scanning electron micrographs displayed a dendritic morphology when deposited at potentials <0.5 V (vs. RHE), whereas spherical aggregates were obtained at potentials >0.5 V. Transmission electron micrographs and X-ray diffraction pattern confirmed the difference in morphological features and growth of Pd dendrites. Pd deposited at 0.4 V showed higher electrochemical surface area of 128.5 m2 g−1 in comparison to 25.1 m2 g−1 obtained for Pd deposited at 0.5 V and also displayed enhanced activity towards formic acid oxidation.

Multiwalled carbon nanotubes (CNTs) functionalized by oxygen plasma were used as a support for platinum-ruthenium nanoparticles for electrochemical methanol oxidation. The influence of plasma treatment time on the electrocatalytic activity was investigated by cyclic voltammetry, CO stripping voltammetry, and chronoamperometry. The electrocatalysts were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results showed that oxygen plasma treatment led to the formation of -CO and -COO groups on the CNT surface. Platinum-ruthenium nanoparticles dispersed with an optimum plasma treatment time of 30 min exhibited the maximum catalytic activity towards methanol oxidation. The rationale for the high catalytic activity is discussed.

Suitability of low Ni austenitic stainless steel (201 SS) as an effective alternative to 316L stainless steel bipolar plates for proton exchange membrane fuel cells (PEMFC) was investigated. Polarization studies showed 201 SS behaved similar to 316L in the cathodic environment of fuel cell, but performed poorly in the anodic environment. Electrochemical impedance spectroscopy (EIS) studies revealed that in the anodic environment the oxide thickness and resistance of 201 SS is lower than 316L, whereas in the cathodic environment both steels showed similar behavior. Mott-Schottky analysis revealed that the defect concentration in oxide layer is higher for 201 SS at the anodic environment, whereas the oxide stability is better than 316L at the cathodic environment. The interfacial contact resistance (ICR) for both the steels was similar.

In a microbial fuel cell (MFC) the reduction reaction at cathode has been a limiting factor in achieving maximum power density, and numerous strategies have been implemented in an attempt to overcome this. Herein, we demonstrate that carbon xerogel (CX) doped with iron (Fe) and nitrogen (N) followed by modification with graphene oxide (GO) is an efficient catalyst for MFCs. The CXFeNGO catalyst was characterized using a scanning electron microscope, and X-ray diffraction, and the catalytic activity was confirmed using cyclic voltammetry studies. At the anode, colonization of bacterial cells on the electrode surface, forming a biofilm, was observed. When the CXFeNGO-modified electrode was used at the cathode in the MFC, a maximum power density of 176.5 ± 6 mW m −2 was obtained, compared to that of plain graphite electrode, which produced 139.1 ± 4 mW m −2 . The power density of the modified electrode is thus 26.8% higher. The power density further increased to 48.6% when the pH of the catholyte was increased to 12, producing a power density of 207 ± 4 mW m −2 .

In this investigation, the effect of embedding nanocomposite with different morphology in a polymer-based reverse osmosis (RO) membrane was studied. Thin-film-nanocomposite (TFN) RO membrane was prepared with graphene oxide (GO) and amino-functionalized zinc oxide (ZnO) having different morphologies, i.e. spherical (ZnO-S), flower (ZnO-F) and rod (ZnO-R) shaped nanostructure. The surface properties of the fabricated TFN-RO membrane were investigated using SEM, TEM, XRD, FTIR, AFM, XPS and contact angle measurement. The membrane performance was evaluated using a cross-flow filtration set-up at 25 °C and 20 bar pressure for 2000 mg/L NaCl solution. The experimental results indicated that 0.02 wt% GO-ZnO composite membranes (regardless of their shape) exhibited enhanced hydrophilicity, flux, and permeability. A comparison of different GO-ZnO morphology highlighted that the GO-ZnO-S TFN-RO membrane exhibited superior performance due to the smaller size of ZnO-S, which effectively prevented GO nanosheets from stacking together. The modified membrane with an optimum GO-ZnO-S concentration of 0.02 wt% showed higher solute water flux (31.42 L/m2·h) compared to the pristine TFC membrane (14.28 L/m2·h) with a good salt rejection. Moreover, the modified membranes were found to be chlorine resistant and showed better anti-fouling performance compared to the pristine membrane.

Electrodeposition of Pd was carried out on Vulcan coated graphite (VCG) substrate by cyclic voltammetry (CV) technique. The VCG was electrochemically activated prior to Pd deposition, and an increase in intensity ratio (ID/G) from 0.17 to 1.24 between the D-band and G-band was observed in the Raman spectra. The increase in ID/G suggests the presence of more structural defects and improved hydrophilicity with the increase in number of electrochemical activation cycles. Scanning electron micrographs showed a transition of Pd morphology from spheres to dendrites with the increase in activation cycles. The activity of the electrodeposited Pd catalysts towards oxygen reduction reaction (ORR) in acidic media showed an increase in the cathodic current confirming the reduction of oxygen, and the current density increased with the increasing cycles of electrochemical activation. The results indicate, insertion of defects on the VCG substrate during electrochemical activation favored good metal-support interaction, resulting in a dendritic morphology with enhanced ORR activity.