We report the efficient electrocatalytic oxidation of glycerol (Gly) and ethylene glycol (EG) using a thin film of gold-curcumin (Au-CM) nanocomposite deposited on a glassy carbon electrode. The nanocomposite was synthesized using a galvanostatic technique in a two-electrode system with a very low current of 0.5 mA. Extensive characterization confirmed that the deposit consists of gold nanoparticles in a porous curcumin envelope. The Au-CM/GCE showed excellent catalytic activity for the electrocatalytic oxidation of Gly and EG with a low activation energy of 20.7 and 49.7 kJ mol-1 and a low onset potential of -0.17 V and -0.14 V, respectively.

Gold nanoparticles (AuNPs) possess tunable size-and shape-dependent properties that are ideal for catalytic properties for many applications. However, the challenge lies in the synthesis of highly stable and ultra-small NPs. We report an energy-efficient galvanostatic route to engineer gold-curcumin (Au-CM) nanocomposites constituting small-sized (-2 nm) AuNPs enveloped by a porous network of curcumin. During electrolytic deposition, the in situ formed Au-CM complexes are the key for the low current involved in our electrosynthesis, which ultimately deposits as CM-enveloped AuNPs at the cathode (Au-CM/GCE). The DFT study also presented high binding energy (18.76 eV) of Au-CM complex in the solvent phase. The Au-CM/GCE nanocomposite exhibited excellent stability (-200 cycles), facile electron transfer ability, catalytic activity, and low Arrhenius energy of 42 and 45 kJ mol(-1), respectively, towards electrooxidation of EtOH and MeOH in alkaline medium. The oxidation kinetics are comparable to those of the best gold-polymer composites. This study points the way for one-pot green synthesis of other engineered electrocatalysts for different applications.

Engineering nanomaterials for non-invasive electrochemical detection of dopamine (DA) in biological samples has been daunting. We report a novel gold-curcumin (Au-CM) nanocomposite as an electrochemical sensor for real-time ultra-selective detection of DA in urine samples. Gold nanoparticles (∼2–3 nm) encased in porous curcumin (CM) network on the surface of a glassy carbon electrode were synthesized via a galvanostatic method and used as the electrochemical sensor. The modified electrode exhibited excellent sensitivity and selectivity toward DA sensing with a record-low limit of detection (LOD) of 3 pM (signal-to-noise ratio of 3). Our DFT-D3 calculations revealed a higher (by 23.3 kJ mol −1 ) adsorption energy of DA on the Au-CM nanocomposite than on the bare Au nanocluster. Furthermore, a wide range of detection 1 pM − 400 μ M ( R 2 = 0.99) was achieved at pH 6. Real-time DA detection was successfully performed in pharmaceutical formulations and urine samples with a single step of dilution with results comparable to clinical values, thus overcoming the complexity of biofluids.

Abstract We developed a surfactant-free spray coating process to coat commercial cellulose-based paper with carbon nanotubes (CNTs) and prepared paper-CNTs current collectors for Li-ion batteries (LIBs). The paper-CNTs were used as current collectors for replacing conventional aluminum foil. Li-ion batteries assembled using paper-CNTs were coated with LiFePO4 as the active material and used as cathodes with Li as the anode, and the assembled LIBs showed a high energy density of 460 Wh kg−1 at a power density of 250 W kg−1. These electrodes were stable even at a current density as high as 600 mA g−1, and showed cycling stability for ~450 cycles at 150 mAh g−1. Furthermore, paper-CNTs based electrodes showed ~17% improvement in areal capacity compared to commercial aluminum-based electrodes suggesting that paper-CNTs can readily displace Al foils as current collectors. Summary: Paper based current collectors have been proposed as a cost-effective and simple replacement for aluminum current collectors. This has been achieved by a scalable spray coating of CNTs on printing papers without any surfactants or binders and subsequently testing them as current collectors for Li-ion batteries.

Resistive interfaces within the electrodes limit the energy and power densities of a battery, for example, a Li-ion battery (LIB). Typically, active materials are mixed with conductive additives in organic solvents to form a slurry, which is then coated on current collectors (e.g., bare or carbon-coated Al foils) to reduce the inherent resistance of the active material. Although many approaches using nanomaterials to either replace Al foils or improve conductivity within the active materials have been previously demonstrated, the resistance at the current collector active material interface (CCAMI), a key factor for enhancing the energy and power densities, remains unaddressed. We show that carbon nanotubes (CNTs), either directly grown or spray-coated on Al foils, are highly effective in reducing the CCAMI resistance of traditional LIB cathode materials (LiFePO4 or LFP and LiNi0.33Co0.33Mn0.33O2 or NMC). Moreover, the CNT coatings displace the need for currently used toxic organic solvents (e.g., N-methyl-2-pyrrolidone) by providing capillary channels, which improve the wetting of aqueous dispersions containing active materials. The vertically aligned CNT-coated electrodes exhibited energy densities as high as (1) ∼500 W h kg-1 at ∼170 W kg-1 for LFP and (2) ∼760 W h kg-1 at ∼570 W kg-1 for NMC. The LIBs with CCAMI-engineered electrodes withstood discharge rates as high as 600 mA g-1 for 500 cycles in the case of LFP, where commercial electrodes failed. The CNT-based CCAMI engineering approach is versatile with wide applicability to improve the performance of even textured active materials for both cathodes and anodes.

Battery electrode microstructure strongly affects the mixed ionic / electronic conduction in electrodes that is necessary to achieve rapid charging / discharging, especially in very thick electrodes. Thick electrodes having low porosity will not provide access of the full electrode structure to electrolyte ions, which will limit the effective capacity at high rates. One strategy for combating this limitation is to incorporate macroscopic pores into the electrode. Electrolyte-filled macropores provide an electrolyte reservoir that can provide ions needed for rapid charging / discharging of a thick electrode, due to the shorter overall distance that ions have to travel during charge / discharge. This talk will present recent work on the use of freeze tape casting with water-based electrode slurries to create thick electrodes having large macroscopic through-pores that run perpendicular to the electrode plane. Electrodes having similar mass loading can be charged / discharged more rapidly when these macropores are present, compared with electrodes that do not have macropores. Implications of the work for fabrication of very thick electrodes capable of rapid charging / discharging will be discussed. Figure 1

Rechargeable batteries (e.g., Li-ion) are widely used to power a number of portable electronic devices such as mobile phones and laptops. Li-ion batteries (LIBs) in particular have revolutionized electric vehicle technology, nonetheless, they suffer from poor energy and power densities, which ultimately limit the driving range and increase the cost. Recently, silicon (Si) anode has attracted a considerable attention from battery researchers as an alternative to conventional graphite anode due to its high specific capacitance (4200 mAh g-1) corresponding to Li22Si5. However successful commercialization of Si anodes in battery packs is hindered by the irreversible capacity loss during cycling associated with volume expansion (~300%), finally leading to electrode failure. In recent times, there have been a number of reports claiming high specific capacities for Si composites but they involve complex synthesis steps leading to higher cost. In this poster, we will discuss our approach of making a composite with CNTs and commercial Si using ultrasonication method. Carbon nanotubes (CNTs) have excellent electrical conductivity and mechanical stability. The composite electrodes when assembled into a battery showed excellent electrochemical performance: albeit small losses in coulombic efficiency during initial six cycles, they retained 100% efficiency for more than 150 cycles. This could be attributed to the inclusion of CNTs which form a flexible network around Si particles, and facilitates volume expansion/contraction during reduction/oxidation of the electrode. Such modification of Si anodes can be seamlessly integrated into commercial manufacturing.

Li-ion rechargeable batteries (LIBs) are the most promising candidates for use in electric and hybrid electric vehicles (EVs and HEVs) due to their high operating voltage and superior energy density compared to other conventional batteries such as the Ni-metal hydride battery. To enable cost-effective and long-lasting EVs, DoE estimates that the performance of present battery systems must be improved by at least four times without increasing the cost. LiFePO4 (LFP) emerged as a competitive cathode material for next-generation LIBs due to its remarkable stability and non-toxicity but they suffer from low electrical conductivity. While the addition of carbon improves the in-plane electrical conductivity, it fails to provide a conducting interface between the LFP/C/binder film and the current collector. This interfacial resistance at the current collector and active material interface (CCAMI) is critical for achieving high power density and rate capability but is often neglected. We addressed this issue by engineering the CCAMI with carbon nanotubes (CNTs). Previously, we demonstrated two roll-to-roll binder-free processes for coating Al foils with CNTS: (i) a CVD-based process for directly growing vertically aligned CNTs (VACNTs) on bare kitchen-grade Al foils [1], and (ii) a spray-coating process for coating industrial-grade Al foils with randomly oriented CNTs [2]. The above mentioned processes eliminate the need for a binder and thereby reduce both the dead weight of the inactive material and the CCAMI resistance. Specifically, we found that the VACNTs- or randomly oriented CNTs-coated Al foils obtained via our roll-to-roll processes enhance the areal (/gravimetric) capacity of LFP by >65% (/>50%) at low C-rates (<2 C), and by >85% (>70%) at high C-rates (>2 C). Moreover, the improved CCAMI resulted in gravimetric energy densities up to 360 Wh/kg and power densities up to 200 W/kg with much higher power capability (increased charge capacity at high discharge rates). Thus, this study describes an attractive approach for improved CCAMI, which is scalable and compatible with existing industrial protocols for coating LFP and takes us many steps closer to the commercial deployment of LIBs in HEVs and EVs. [1] M. R. Arcila-Velez et al., Nano Energy. 8 (2014) 9–16. doi:10.1016/j.nanoen.2014.05.004. [2] M. Karakaya et al., Appl. Phys. Lett. 105 (2014). doi:10.1063/1.4905153.

Graphene due to its high surface area and superior conductivity has attracted wide attention from both industrial and scientific communities. We chose graphene as a substrate for metal nanoparticle deposition with possible fuel cell applications. There are many chemical routes for fabrication of metal-graphene composites, but they have an inherent disadvantage of low performance due to the usage of surfactants, that adsorb on their surface. Here we present a design for one pot synthesis of gold nanoparticles and simultaneous deposition on graphene with laser ablation of gold strip and functionalized graphene. In this process there are two natural advantages, the nanoparticles are synthesized without any surfactants, therefore they are pristine and subsequent impregnation on graphene is linker free. These materials are well characterized with electron microscopy to find their morphology and spectroscopic techniques like Raman, UV-Vis. for functionality. This gold nanoparticle decorated graphene composite has been tested for its electrocatalytic oxidation of alcohols for alkaline fuel cell applications. An electrode made of this composite showed good stability for more than 200 cycles of operation and reported a low onset potential of 100 mV more negative, an important factor for direct extracting energy from ethanol. Figure 1

A facile surfactant free laser ablation mediated synthesis (LAMS) of gold-graphene composite is reported here. The material was characterized using transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, powdered X-ray diffraction, Raman spectroscopy, Zeta potential measurements and UV-Visible spectroscopic techniques. The as-synthesized gold-graphene composite was effectively utilized as catalyst for decolorization of 4 important textile and laser dyes. The integration of gold nanoparticles (AuNPs) with high surface area graphene has enhanced the catalytic activity of AuNPs. This enhanced activity is attributed to the synergistic interplay of pristine gold's electronic relay and pi-pi stacking of graphene with the dyes. This is evident when the Rhodamine B (RB) reduction rate of the composite is nearly twice faster than that of commercial citrate capped AuNPs of similar size. In case of Methylene blue (MB) the rate of reduction is 17,000 times faster than uncatalyzed reaction. This synthetic method opens door to laser ablation based fabrication of metal catalysts on graphene for improved performance without the aid of linkers and surfactants. (C) 2014 Elsevier B.V. All rights reserved.

A well-known limitation in the fabrication of metal-graphene composite has been the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. We demonstrate here a novel one-pot synthesis of gold nanoparticles by laser ablation of gold strip and in-situ decoration on graphene substrate. Not only the impregnation of nanoparticles was linker free, but also the synthesis by itself was surfactant-free. The composite materials were well characterized morphologically and functionally using electron microscopy, Xray and electron diffraction, Raman spectroscopy, Zeta potential, electrochemical measurements and UV-Visible spectroscopic techniques. This linker-free gold-graphene based composite has been employed for catalytic applications pertaining to electrooxidation. We have explored the use of this composite as a binder-free electrode in electrocatalytic oxidation of methanol and ethanol in alkaline medium. Additionally, the onset potential for ethanol oxidation was found to be more negative, -100 mV, an indication of its promising application in direct ethanol fuel cells.

Microwave induced reactions for immobilizing platinum and palladium nanoparticles on multiwall carbon nanotubes are presented. The resulting hybrid materials were used as catalysts for direct methanol, ethanol and formic acid oxidation in acidic as well as alkaline media. The electrodes are formed by simply mixing the hybrids with graphite paste, thus using a relatively small quantity of the precious metal. We report Tafel slopes and apparent activation energies at different potentials and temperatures. Ethanol electro-oxidation with the palladium hybrid showed an activation energy of 7.64 kJmol(-1) which is lower than those observed for other systems. This system is economically attractive because Pd is significantly less expensive than Pt and ethanol is fast evolving as a commercial biofuel.