Towards Mixed Fuels: The Electrochemistry of Hydrazine in the Presence of Methanol and Formic Acid

Abstract

The electrochemistry of formic acid, carbon monoxide and methanol have been investigated and evaluated in combination with hydrazine. Hydrazine was observed to display the anticipated steady-state oxidation waves at platinum (Pt) microelectrodes by cyclic voltammetry, and upon introduction of carbon monoxide (CO) gas, the Pt surface was fully passivated (prior to CO oxidation). However, the two individual responses of hydrazine and formic acid (HCOOH) are to be additive when combined in solution. No detrimental effects were observed upon the hydrazine voltammetry, even in the presence of excess formic acid, despite formic acid clearly displaying characteristic self-poisoning tendencies (primarily due to the formation of CO) in its own voltammetry. Effects intermediate to those of CO and formic acid were observed when methanol was present. Currents were essentially additive at low methanol content, but hydrazine oxidation current decreased by about 40% when an 100-fold excess of methanol was present, corresponding to poisoning by methanol dehydrogenation intermediates. These results are discussed with relevance to mixed fuels for more flexible or powerful fuel cells, and the possible formation of a random microelectrode array (templated by strongly adsorbed poison) on the microelectrode surface.

Electroanalytical properties of screen printed shallow recessed electrodes

“…iron(III) oxide graphite composite electrodes (1.18 mM) 41 and iron phthalocyanine film upon a gold macro electrode (11 mM), 42 the PtdrSPE offers the unique advantage of being screen printed, with the key attribute of the electrode being the simple configuration with the onboard additions of a reference and counter electrode, in addition to this, no prior treatment of the electrode, nor sample is required with the necessity for potential cycling alleviated as is required in other studies. 43,44 The PtdrSPE was further utilised for the sensing of hydrogen peroxide, first cyclic voltammetric studies were carried out determining the reduction potential of hydrogen peroxide in a pH 7 phosphate buffer solution to be +0.35 V (vs. Ag/AgCl) in agreement with previous reports. 39 Consequently, chronoamperometric measurements (+0.35 V, 120 s) for the addition of hydrogen peroxide into a pH 7 phosphate buffer solution were obtained over the range 100 to 1000 mM (I/mA ¼ 2.085 Â 10 À2 mA/mM + 4.066 Â 10 À4 mA; R 2 ¼ 0.99, N ¼ 10).…”

Platinum screen printed electrodes for the electroanalytical sensing of hydrazine and hydrogen peroxide

“…Such requirements are negated through the use of the PtSPE, which is also not found to compromise the low detection limits. Interestingly, the PtSPE has an inherent advantage over that of platinum microelectrodes, where Aldous and Compton 67,68 demonstrate that variable results can be achieved which is greatly dependant on the history of the electrode with optimal results observed at oxidised platinum surfaces; extensive pretreatment in the form of potential cycling 67,68 needs to be applied to ensure generation of the platinum oxide but in our case, such a step is negated since the platinum is in the form of an oxide upon the screen printed surface greatly simplifying the analytical protocol.…”

“…We have reported the application of novel, disposable, singleshot platinum screen printed electrodes and explores its analytical performance towards the sensing of hydrazine and hydrogen peroxide which is found to exhibit analytically useful linear ranges and limits of detection compared to existing methodologies. The added benefit is that the platinum resides as an oxide which is beneficial for hydrazine 67,68 since the need to produce platinum oxides via extensive potential cycling on platinum electrodes is alleviated greatly simplifying the analytical protocol.…”

Liquid fuel cells

“…In addition to individual compounds, mixtures can be used to improve electrode kinetics. Hydrazine, for example, was mixed with formic acid and methanol for that purpose [26]. …”