Bruno G. Pollet

Nano-sized Co/Co(OH) 2 core-shell structure synthesized in molten salt as electrode materials for supercapacitors

A facile and low cost molten salt method for the synthesis of Co@Co(OH)2 core-shell nanostructured material exhibiting high specific capacitances for supercapacitors was developed. In our conditions, the molten salt acted as solvent and reducing agent for the precipitation and formation of Co-based nano-structures. It was observed that in the Co@Co(OH)2 core-shell nanostructure, Co cores can act as a conductive medium to improve the utilization of Co(OH)2 due to the superior electrical conductivity of Co metal and its high surface area. It was also found that the as-prepared Co@Co(OH)2 exhibited high electrochemical performance as a cathode material in asymmetric supercapacitors, yielding specific capacitance values of up to ~410xa0Fxa0g−1 at 2xa0Axa0g−1 with a retention rate of 90xa0% after 2500xa0cycles. The achievement of high capacitance coupled to a low cost method represents an important step forward in the development of promising electrode materials for alkaline supercapacitor cathodes.

Sonoelectrochemical one-pot synthesis of Pt – Carbon black nanocomposite PEMFC electrocatalyst

Simultaneous electrocatalytic Pt-nanoparticle synthesis and decoration of Vulcan XC-72 carbon black substrate was achieved in a novel one-step-process, combining galvanostatic pulsed electrodeposition and pulsed ultrasonication with high power, low-frequency (20kHz) ultrasound. Aqueous chloroplatinic acid precursor baths, as well as carbon black suspensions in the former, were examined and decoration was proven by a combination of characterization methods, namely: dynamic light scattering, transmission electron microscopy, scanning electron microscopy with EDX-analysis and cyclic voltammetry. In particular, PVP was shown to have a beneficial stabilizing effect against free nanoparticle aggregation, ensuring narrow size distributions of the nanoparticles synthesized, but is also postulated to prevent the establishment of a strong metal-substrate interaction. Current pulse amplitude was identified as the most critical nanoparticle size-determining parameters, while only small size particles, under 10nm, appeared to be attached to carbon black.

Enhanced Cycleability of Amorphous MnO2 by Covering on α-MnO2 Needles in an Electrochemical Capacitor

An allomorph MnO2@MnO2 core-shell nanostructure was developed via a two-step aqueous reaction method. The data analysis of Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Diffraction and N2 adsorption-desorption isotherms experiments indicated that this unique architecture consisted of a porous layer of amorphous-MnO2 nano-sheets which were well grown onto the surface of α-MnO2 nano-needles. Cyclic voltammetry experiments revealed that the double-layer charging and Faradaic pseudo-capacity of the MnO2@MnO2 capacitor electrode contributed to a specific capacitance of 150.3 F·g−1 at a current density of 0.1 A·g−1. Long cycle life experiments on the as-prepared MnO2@MnO2 sample showed nearly a 99.3% retention after 5000 cycles at a current density of 2 A·g−1. This retention value was found to be significantly higher than those reported for amorphous MnO2-based capacitor electrodes. It was also found that the remarkable cycleability of the MnO2@MnO2 was due to the supporting role of α-MnO2 nano-needle core and the outer amorphous MnO2 layer.

Ultra-high surface area and mesoporous N-doped carbon derived from sheep bones with high electrocatalytic performance toward the oxygen reduction reaction

A nitrogen (N)-doped mesoporous carbon material exhibiting ultra-high surface area was successfully synthesized from sheep bones via a facile and low-cost method. The obtained carbon material had an ultra-high specific surface area of 1961xa0m2xa0g−1 and provided rich active sites for the oxygen reduction reaction (ORR), which in turn resulted in high electrocatalytic activity. It was found that the pore size distribution for the newly prepared carbonaceous material fell in the range of 1–4xa0nm. Benefiting from its high surface area and the presence of pyridine-N and quaternary-N species, the as-prepared carbon material exhibited excellent ORR activity in an oxygen-saturated 0.1xa0M KOH solution, compared to commercial Pt/C (10xa0wt%). Due to its high ORR catalytic activity, stability and low-cost, using sheep bone as C and N precursors to produce N-doped carbon provides an encouraging step toward the goal of replacing commercial Pt/C as fuel cell cathode electrocatalyst.

V2O5-SiO2 hybrid as anode material for aqueous rechargeable lithium batteries

V2O5-SiO2 hybrid material was fabricated by heat-treating a mixture of H2SiO3 and V2O5. SEM, TEM, XRD, and N2 isotherm analyses were performed to characterize the morphology and structure details of the as-prepared V2O5-SiO2. The possibility of using the as-prepared V2O5-SiO2 as anode material for aqueous lithium-ion batteries was investigated. Potentiostatic and galvanostatic results indicated that the intercalation/de-intercalation of Li+ in this material in aqueous electrolyte was quasi-reversible. It was also found that a discharge capacity of up to 199.1xa0mAhxa0g−1 was obtained at a current density of 50xa0mAxa0g−1 in aqueous solution of 1xa0M Li2SO4, a value which is much higher than the available reported capacities of vanadium (+5) oxides in aqueous electrolytes.

Sonoelectrochemical Production of Fuel Cell Nanomaterials

This chapter highlights the use of sonoelectrochemistry for the synthesis of fuel cell nanomaterials which is currently an emerging research area. The chapter also focuses on recent studies of sonoelectrochemical production of noble metals and electrocatalysts for Proton Exchange Membrane Fuel Cells, Solid Oxide Fuel Cells and other Fuel Cells.