Nanofibrous Electrode Research Articles

Nanofibrous Electrodes with Tunable Electrodeposited Pt Morphologies with High ORR Activity and Durability

A new approach for the preparation of PEMFC cathode electrocatalysts based on thin layers of platinum deposited on a support instead of conventional Pt nanoparticles supported on carbon black could be achieved adopting various Pt deposition techniques including atomic layer deposition, electrochemical atomic layer epitaxy, self-terminated Pt electrodeposition, thermal dealloying, and galvanostatic displacement of Ni and Cu ions with Pt1,2. This morphology allows for a more effective utilisation of the highly priced noble metal, while increases the durability of the electrodes over time. The morphology and nature of the support material also plays a crucial role. Nanostructured 1D materials have attracted significant research attention due to the influence of their nanostructure and porosity on performance and durability of the PEMFC3. In this regard, electrospinning is a reliable and scalable technique for the preparation of nanofibers with controlled and uniform diameters and structures. Its versatility allows the production of organic, hybrid and inorganic nanofibres, as well as the possibility of creating different geometries, assemblies and architectures4. We developed novel nanofibrous electrodes (NFE) based on 3D nanostructured networks of carbon nanofibers covered by Pt nanoislands, merging the advantage of Pt thin layers catalyst and a highly porous robust support. This was achieved by combining electrospinning and high overpotential pulsed Pt electrodeposition. These catalysts are based on self-standing electrospun carbon nanofibers covered by platinum thin platinum nanoislands. NFEs are highly durable when compared to commercial standards and have a higher degree of platinum exploitation. Electrochemical active specific surface areas as high as 140 m2g-1 Pt with retention in the order of 70 % after accelerated stress testing are measured, making them a suitable alternative to currently available commercial catalyst. 1. S. M. Alia, Y. Yan, and B. Pivovar, Catal. Sci. Technol., 4, 3589–3600 (2014) 2. G. Ercolano, S. Cavaliere, D. Jones, and J. Rozière, ECS Trans., 69, 1237–1242 (2015). 3. S. Cavaliere et al., ChemElectroChem, 2, 1966–1973 (2015). 4. S. Subianto et al., in Electrospinning for Advanced Energy and Environmental Applications, vol. 1, p. 29–60 (2015).

Nanofibrous Electrode Design By CNT-Winded Pt/TiO2 for Superior PEMFC Performance and Durability at High Temperature

Fuel cell is one of the most promising electrochemical energy conversion devices that has many advantages such as high efficiency, high power density, CO2 free, noise free, rapid start up, etc. Especially, polymer electrolyte membrane fuel cell (PEMFC) has been shown a lot of attention due to its high power density and relatively good portability. Generally, Pt supported on carbon black is used as an electrocatalyst in PEMFC. However, carbon corrosion is one of the main problem for electrode structure collapse and catalyst activity loss, which can be further accelerated at high temperature. Therefore, we need to find an alternative catalyst support material that is electrochemically stable and interacts strongly with the catalyst active sites. Recently, metal oxide supports have been reported as promising materials due to their excellent mechanical resistance and inherently higher stability. Among many candidates, titanium dioxide (TiO2) support has an extraordinary stability under severe acidic atmosphere, which provides the possibility to directly use as a support material. However, the low electrical conductivity, catalytic activity and surface area of TiO2hinder the direct apply to the PEMFC electrode. In order to solve these problems, we prepared TiO2 nanofibers by electrospinning method and platinum nanoparticles are deposited by microwave-assisted polyol method to synthesize an effective electrode catalyst. Then, CNT was winded around the catalyst surface to boost up the electrical conductivity. Furthermore, we found a modified Pt electronic structure that takes advantage of the strong synergetic interactions of TiO2 nanofibers, Pt nanoparticles and winded-CNT. This structure influences on a decrease of the d-band vacancy of Pt due to electron transfer from the support, resulting in an improved oxygen reduction reaction. Therefore, the cathode with the CNT modified Pt/TiO2 nanofiber composite shows higher catalytic activity due to the elimination of the drawback associated with conductivity and enhanced electronic active structure. As from various PEMFC tests, our CNT-Pt/TiO2 catalyst shows superior performance and durability, which is definitely distinguishable at high temperature condition of 120 oC and RH 40% compare to the commercial Pt/C.

Highly flexible binder-free core–shell nanofibrous electrode for lightweight electrochemical energy storage using recycled water bottles

The creation of a novel flexible nanocomposite fiber with conductive polymer polyaniline (PAni) coating on a polyethylene terephthalate (PET) substrate allowed for increased electrochemical performance while retaining ideal mechanical properties such as very high flexibility. Binder-free PAni-wrapped PET (PAni@PET) fiber with a core–shell structure was successfully fabricated through a novel technique. The PET nanofiber substrate was fabricated through an optimized electrospinning method, while the PAni shell was chemically polymerized onto the surface of the nanofibers. The PET substrate can be made directly from recycled PETE1 grade plastic water bottles. The resulting nanofiber with an average diameter of 121 nm ± 39 nm, with a specific surface area of 83.72 m2 g−1, led to better ionic interactions at the electrode/electrolyte interface. The PAni active layer coating was found to be 69 nm in average thickness. The specific capacitance was found to have increased dramatically from pure PAni with carbon binders. The specific capacitance was found to be 347 F g−1 at a relatively high scan rate of 10 mV s−1. The PAni/PET fiber also experienced very little degradation (4.4%) in capacitance after 1500 galvanostatic charge/discharge cycles at a specific current of 1.2 A g−1. The mesoporous structure of the PAni@PET fibrous mat also allowed for tunable capacitance by controlling the pore sizes. This novel fabrication method offers insights for the utilization of recycled PETE1 based bottles as a high performance, low cost, highly flexible supercapacitor device.

Femtosecond laser nanostructuring for femtosensitive DNA detection

In this paper, a new concept to achieve improved probe–target recognition has been devised by introducing a novel class of DNA-functionalized three-dimensional (3D), stand-free, and nanostructured electrodes. The gold nanofibrous electrodes were created using MHZ ultrafast laser material processing in air at ambient conditions. The developed nanofibrous DNA biosensor was characterized by cyclic voltammetry with the use of ferrocyanide as an electrochemical redox indicator. Currently, electrochemical signal enhancement which is of great significance for improving the sensitivity in DNA detection remains a great challenge. Through, enhanced surface area-to-volume ratio and more efficient arrangement of probe molecules on nanofibrous electrodes, our newly developed electrode system overcomes some of the sensitivity challenges of the existing systems. This nanofiber-based system realizes femtomolar (fM) sensitivity toward complementary target DNA, and demonstrates a very wide dynamic range (from 1fM to 1nM).

Sensitive electrochemical detection of superoxide anion using gold nanoparticles distributed poly(methyl methacrylate)–polyaniline core–shell electrospun composite electrode

In the present communication, a novel composite nanofibrous electrode is developed for the detection of superoxide anion (O(2)˙(-)) in phosphate buffered saline (PBS). The composite fiber electrode is fabricated by dispersing gold nanoparticles onto poly(methyl methacrylate) (PMMA)-polyaniline (PANI) core-shell electrospun nanofibers. The constructed architecture is proven to be a favorable environment for the immobilization of the enzyme, superoxide dismutase (SOD). Direct electron transfer is achieved between SOD and the electrode with an electron transfer rate constant of 8.93 s(-1). At an applied potential of +300 mV, PMMA/PANI-Au(nano)/SOD-ESCFM shows highly sensitive detection of O(2)˙(-). In addition to this, quantification of different activities of SOD is realized at PMMA/PANI-Au(nano)/SOD-ESCFM. These analytical features offer great potential for construction of the third-generation O(2)˙(-) biosensor.

The performance of coupled (CdS:CdSe) quantum dot-sensitized TiO 2 nanofibrous solar cells

Highly porous networks and reduced grain boundaries with one-dimensional (1-D) nanofibrous morphology offer enhanced charge transport in solar cells applications. Quantum dot (QDs) decorated TiO 2 nanofibrous electrodes, unlike organic dye sensitizers, can yield multiple carrier generations due to the quantum confinement effect. This paper describes the first attempt to combine these two novel approaches, in which CdS (∼18 nm) and CdSe (∼8 nm) QDs are sensitized onto electrospun TiO 2 nanofibrous (diameter ∼80–100 nm) electrodes. The photovoltaic performances of single (CdS and CdSe) and coupled (CdS/CdSe) QDs-sensitized TiO 2 fibrous electrodes are demonstrated in sandwich-type solar cells using polysulfide electrolyte. The observed difficulties in charge injection and lesser spectral coverage of single QDs-sensitizers are solved by coupling (CdS:CdSe) two QDs-sensitizers, resulting in a enhanced open-circuit voltage (0.64 V) with 2.69% efficiency. These results suggest the versatility of fibrous electrodes in QDs-sensitized solar cell applications.

A novel glucose biosensor based on immobilization of glucose oxidase into multiwall carbon nanotubes–polyelectrolyte-loaded electrospun nanofibrous membrane

Nanofibrous glucose electrodes were fabricated by the immobilization of glucose oxidase (GOx) into an electrospun composite membrane consisting of polymethylmethacrylate (PMMA) dispersed with multiwall carbon nanotubes (MWCNTs) wrapped by a cationic polymer (poly(diallyldimethylammonium chloride) (PDDA)) and this nanofibrous electrode (NFE) is abbreviated as PMMA–MWCNT(PDDA)/GOx–NFE. The NFE was characterized for morphology and electroactivity by using electron microscopy and cyclic voltammetry, respectively. Field emission transmission electron microscopy (FETEM) image reveals the dispersion of MWCNT(PDDA) within the matrix of PMMA. Cyclic voltammetry informs that NFE is suitable for performing surface-confined electrochemical reactions. PMMA–MWCNT(PDDA)/GOx–NFE exhibits excellent electrocatalytic activity towards hydrogen peroxide (H 2O 2) with a pronounced oxidation current at +100 mV. Glucose is amperometrically detected at +100 mV (vs. Ag/AgCl) in 0.1 M phosphate buffer solution (PBS, pH 7). The linear response for glucose detection is in the range of 20 μM to 15 mM with a detection limit of 1 μM and a shorter response time of ∼4 s. The superior performance of PMMA–MWCNT(PDDA)/GOx–NFE is due to the wrapping of PDDA over MWCNTs that binds GOx through electrostatic interactions. As a result, an effective electron mediation is achieved. A layer of nafion is made over PMMA–MWCNT(PDDA)/GOx–NFE that significantly suppressed the electrochemical interference from ascorbic acid or uric acid. In all, PMMA–MWCNT(PDDA)/GOx–nafion–NFE has exhibited excellent properties for the sensitive determination of glucose like high selectivity, good reproducibility, remarkable stability and without interference from other co-existing electroactive species.

Anode and Cathode Templated Three-dimensional Lithium Ion Batteries Based on Nano-fibrous Electrodes

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