Sneh L. Jain

Electrochemical performance of a hybrid direct carbon fuel cell powered by pyrolysed MDF

Medium density fibreboard is a ubiquitous element in modern furniture, here we consider utilising waste MDF as a future energy source. In particular, we focus upon the hybrid direct carbon fuel cell (HDCFC), which involves a combined molten carbonate/solid oxide fuel cell anode/electrolyte interface and can be fuelled by a wide range of carbon forms. Current–voltage measurements and a.c. impedance at temperatures in the range of 525–800 °C have been made on cells powered by pyrolysed medium density fibreboard (pMDF) samples which had undergone three different preparatory treatments (immersion of strips in molten eutectic carbonate mixture; deep soaking of strips in aqueous carbonate mixture corresponding to the eutectic composition and fine powdering). Below 700 °C the three pMDF samples show quite different electrochemical performance in the HDCFC, but above 700 °C their behaviour becomes similar. Powdered pMDF gives the best OCV (0.89 V) and lowest resistance (2.36 Ω) values below 700 °C, although the electrochemical performance is dominated by diffusion limitations and the performance degrades at higher temperatures. The immersed strip behaves quite differently with limited performance below 750 °C but it shows both good OCV, 1 V, and low resistance, <4 Ω, at higher temperatures. Three components are discernable, an ohmic contribution probably due to both ionic resistance of zirconia electrolyte and electronic resistance of current collection and two electrode processes thought to be associated with the transfer of oxygen ions at the electrode : electrolyte interface and diffusion of reactant species through the electrode. The activation energies calculated from the ohmic resistances for the three samples (−0.79 – −1.00 eV) are of similar order to that expected for the yttria zirconia electrolyte.

A Novel Direct Carbon Fuel Cell Concept

This paper describes a direct carbon fuel cell (DCFC) based on a solid oxide fuel cell (SOFC) system which has been used to assess the performance of a high surface area carbon fuel material. The cell, consisting of a co-fired anode, electrolyte, and cathode, has been produced by standard tape casting methods and is of tubular geometry. The operating conditions of the cell require a 62 mol% Li 2 CO 3 and 38 mol% K 2 CΟ 3 eutectic secondary electrolyte and the operation of the cell is described over the temperature range 525-700°C. The cell performance has been examined by standard electrochemical methods.

Carbon Content in a Direct Carbon Fuel Cell

In direct carbon fuel cells (DCFCs), elemental carbon is directly oxidised electrochemically to generate electrical power. Carbon is readily available, easily transported and stored and, therefore, affordable to the global energy economy. Further operational advantages include the use of a fully renewable solid bio-carbon fuel source and the opportunity for scale-up. Herein we discuss a DCFC which utilises a molten mixed alkali metal carbonate eutectic as a secondary electrolyte, contained within a solid oxide fuel cell. The operation of the cells over an extended temperature range (525-700 oC) was examined using standard electrochemical methods. We will present the electrochemical performance of Super S, a high surface area carbon black.

Spectroelectrochemistry of copper(II) complexes with deprotonated tetradentate pyridine-2-carboxamide ligands: EC reaction of the electrogenerated Cu(III) species

Abstract The electrochemistry of [CuL 1 ] 1 and [CuL 2 ] 2 [H 2 L 1 =1,2-bis(pyridine-2-carboxamido)benzene, H 2 L 2 =3,4-bis(pyridine-2-carboxamido)toluene] was investigated. Both complexes show a quasi-reversible Cu(II/I) reduction near −1.6 V vs Fc + /Fc. Spectroelectrochemistry confirmed that the Cu(III) state is accessible near +0.4 V, and undergoes an EC reaction ( k ≃10 s −1 ) to generate a new Cu(II) species.

Kinetics of the Reaction of Mer-Tris(Picolinato) Iron(III) with Hydrogen Peroxide in Pyridine: Role of Hydroxyl Radicals in Subsequent Catalytic Oxygenation of Cyclohexane to the Ketone.

Reaction of pale-green high spin mer-tris(picolinato)iron(III) with t-butylhydroperoxide in pyridine gives rise to an EPR signal for the t-butylperoxyl radical via a short lived purple intermediate which itself decays eventually to a yellow-brown high spin iron(III) product. The kinetics of the corresponding reaction with hydrogen peroxide have been studied in regard to the dependence of the hydrogen peroxide and picolinic acid concentration on the rate of the initial stages. The results support two rate-determining initial steps (minutes) involving the formation of a short lived purple high spin hydroperoxoor tbutylperoxoiron(III) intermediate (λmax = 530 nm, ε ~ 1,000 dm3 mol-1 cm-1 for the hydroperoxo species) via pre-equilibrium loss of one picolinic acid which then undergoes homolytic Fe-O bond cleavage to give iron(II) and hydroperoxyl (t-butylperoxyl) radical resulting in eventual formation of deep yellow-brown solution which undergoes further complex UV-visible changes over a period of several hours. During this latter timescale these solutions are able to carry out Gif-type catalytic oxygenation of cyclohexane to cyclohexanone in the presence of H2O2 (or O2/pyH/Zn powder) a process which however is completely inhibited in the presence of small amounts of dimethylsulfoxide, an efficient scavenger of the hydroxyl radical. Bis(picolinato)copper(II) was found to be a poor oxygenation catalyst, a finding consistent with its inability to generate the hydroxyl radical via Cu(I) under the same conditions. These results confirm that generation of hydroxyl radicals (via reaction of H2O2 with iron(II) or any other suitably reactive lower valent state) is central to the oxygenation chemistry carried out by these solutions.

Cobalt(II) frameworks of 3,3 '-bipyridyl-5,5 '-dicarboxylate(bpdc(2-)). X-ray crystal structures of [Co(bpdc)(H2O2)(2)](n) and {[Co(bpdc)(H2O4]center dot 2H(2)O}(n)

Sodium 3,3′-bipyridyl-5,5′-dicarboxylate (Na2bpdc) reacts with cobalt(II) chloride under hydrothermal conditions to give the guest-free two-dimensional framework [Co(bpdc)(H2O)2] n 1 and at ambient temperature to generate the one-dimensional polymer {[Co(bpdc)(H2O)4].2H2O} n 2. In 1 the bpdc2- ligand is tetradentate, coordinating through the pyridyl nitrogens and two of the carboxylate oxygen atoms, in 2 solely the nitrogen atoms of this ligand bind to cobalt.

The reaction of [Fe(pic)3] with hydrogen peroxide: a UV-visible and EPR spectroscopic study (Hpic = picolinic acid).

The Gif family of catalysts, based on an iron salt and O2 or H2O2 in pyridine, allows the oxygenation of cyclic saturated hydrocarbons to ketones and alcohols under mild conditions. The reaction between [Fe(pic)3] and hydrogen peroxide in pyridine under GoAgg(III)(Fe(III)/Hpic catalyst) conditions was investigated by UV-visible spectrophotometry. Reactions were monitored at 430 and 520 nm over periods ranging from a few minutes to several hours at 20 degrees C. A number of kinetically stable intermediates were detected, and their relevance to the processes involved in the assembly of the active GoAgg(III) catalyst was determined by measuring the kinetics in the presence and absence of cyclohexane. EPR measurements at 110 K using hydrogen peroxide and t-BuOOH as oxidants were used to further probe these intermediates. Our results indicate that in wet pyridine [Fe(pic)3] undergoes reversible dissociation of one picolinate ligand, establishing an equilibrium with [Fe(pic)2(py)(OH)]. Addition of aqueous hydrogen peroxide rapidly generates the high-spin complex [Fe(pic)2(py)(eta1-OOH)] from the labilised hydroxy species. Subsequently the hydroperoxy species undergoes homolysis of the Fe-O bond, generating HOO. and [Fe(pic)2(py)2], the active oxygenation catalyst.

X-Ray crystal structures of trans-6,13-dimethyl-6,13-diamino-1,4,8, 11-tetraazacyclotetradecane.6HCl.2H2O and its condensation product with pyridine-2-carboxaldehyde

The X-ray crystal structures of trans-6,13-dimethyl-6,13-diamino-1,4,8,11-tetraazacyclotetradecane hexahydrochloride dihydrate (trans-diammac.6HCl.2H2O) and the product 1 derived by condensation of trans-diammac with pyridine-2-carboxaldehyde, have been determined. For 1 intramolecular attack of macrocycle amine nitrogen atoms on the C=N bonds of the intermediate diimine gives a ring-closed tautomeric form, which comprises two imidazolidine rings fused to the macrocycle.