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.

http://repository.ust.hk/ir/bitstream/1783.1-77094/1/acs.chemrev.5b00462_withlink.pdf

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

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...

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

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...

Molecularly Imprinted Polymers

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

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

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.

http://ma.ecsdl.org/content/MA2005-02/33/1168.full.pdf

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

Vanadium redox flow battery (VRFB) is an energy storage system, wherein V2+/V3+ and VO2+/VO2+ are used as negative and positive electrolyte respectively. It is well known that, V2+/V3+ redox reaction is sluggish in comparison to that of VO2+/VO2+ reaction. As the redox potential of V2+/V3+ redox-couple is more negative to that of H+/H2 redox-couple, during the V2+ formation hydrogen evolution occurs concomitantly, which affects the capacity retention of VRFB inducing redox couples concentration imbalance between the positive and negative electrolytes. In this study, we have explored the beneficial effect of D-fructose as an additive to the negative electrolyte. D-fructose (i) enhances the interfacial area of the graphite felt negative electrode-electrolyte interface by wetting, thereby the current due to V2+/V3+ redox reaction at a given overpotential, (ii) suppresses the H2 evolution at negative electrode during charging of VRFB (iii) controls the VO2+ accumulation at the positive electrolyte and (iv) chemically reduces the VO2+ arriving at negative electrode side through crossover, thereby avoiding the direct reaction between V2+ and VO2+. A capacity retention of 86 % and 25 % is achieved at the end of the 25th cycle in the presence and absence of D-fructose in the negative electrolyte, respectively. This way of in-situ redox balancing alleviates the requirement for external redox balancing of the electrolyte, and help VRFB to deliver constant capacity with cycles.

On In–situ Redox Balancing of Vanadium Redox Flow Battery Using D-Fructose as Negative Electrolyte Additive

http://jes.ecsdl.org/content/164/7/A1720.full.pdf

Introduction of Carbonyl Groups: An Approach to Enhance Electrochemical Performance of Conjugated Dicarboxylate for Li-Ion Batteries

Nitrogen Functionalized Few Layer Graphene Derived from Metal-Organic Compound: A Catalyst for Oxygen Reduction Reaction

This work deals about the development of paper-based fuel cells with high open-circuit voltages for application in powering the micro-nanosystems such as bio-sensors. The developed fuel cell employs Whatman paper as the ion conductor placed between the anode and the cathode to replace expensive ion-conducting membranes such as Nafion. A maximum open-circuit voltage of ∼2.1 V per single cell and a power output of ∼4.5 mW cm−2 at ∼6 mA cm−2 are obtained when employing 1 M NaBH4 in 20 wt% NaOH solution and 1 M VO2
 + in 2.5 M H2SO4 solution. Chronoamperometric measurement performed at 1 V indicates that the output power density varies from 6 to 1 mW cm−2 in about 100 min. The power delivered at the end of even 100 min is comparable to that of the peak power delivered by many of the micro-fuel cell systems reported in the literature.

Flexible paper-based borohydride-vanadium fuel cell for powering micro-nanosystems

A new, simple, green method for the synthesis of Au nanowires (average diameter 8 nm and several micrometers in length) using Au seeds prepared from bael gum (BG) is reported. The nanowires are characterized using UV–visible absorption spectroscopy, powder X-ray diffraction, transmission electron microscopy (TEM), and high-resolution-TEM. It is observed that the rate of the reduction process might be the decisive factor for the shape selectivity, as evident from the formation of nanowires at a particular concentration of seeds and NaOH. The polysaccharide present in BG is the active ingredient for the synthesis of Au nanowires, while the small molecules present in BG, when used alone, did not result in nanowire formation. The TEM images of the precursor to the Au nanowires suggested that new, nucleated particles align in a linear manner and fuse with one another, resulting in the nanowire. The linear fusion of the newly nucleated particles could be due to the lack of adequate protecting agent and the pres...

Kothandaraman Ramanujam

Papers

On In–situ Redox Balancing of Vanadium Redox Flow Battery Using D-Fructose as Negative Electrolyte Additive

Introduction of Carbonyl Groups: An Approach to Enhance Electrochemical Performance of Conjugated Dicarboxylate for Li-Ion Batteries

Nitrogen Functionalized Few Layer Graphene Derived from Metal-Organic Compound: A Catalyst for Oxygen Reduction Reaction

Flexible paper-based borohydride-vanadium fuel cell for powering micro-nanosystems

Green, Seed-Mediated Synthesis of Au Nanowires and Their Efficient Electrocatalytic Activity in Oxygen Reduction Reaction.