Temperature (Over)Compensation in an Oscillatory Surface Reaction

Abstract

Biological rhythms are regulated by homeostatic mechanisms that assure that physiological clocks function reliably independent of temperature changes in the environment. Temperature compensation, the independence of the oscillatory period on temperature, is known to play a central role in many biological rhythms, but it is rather rare in chemical oscillators. We study the influence of temperature on the oscillatory dynamics during the catalytic oxidation of formic acid on a polycrystalline platinum electrode. The experiments are performed at five temperatures from 5 to 25°C, and the oscillations are studied under galvanostatic control. Under oscillatory conditions, only non-Arrhenius behavior is observed. Overcompensation with temperature coefficient (q 10 , defined as the ratio between the rate constants at temperature T + 10°C and at T) < 1 is found in most cases, except that temperature compensation with q 10 ≈ 1 predominates at high applied currents. The behavior of the period and the amplitude result from a complex interplay between temperature and applied current or, equivalently, the distance from thermodynamic equilibrium. High, positive apparent activation energies were obtained under voltammetric, nonoscillatory conditions, which implies that the non-Arrhenius behavior observed under oscillatory conditions results from the interplay among reaction steps rather than from a weak temperature dependence of the individual steps.

Effect of temperature on the electro-oxidation of ethanol on platinum

“…Estimating the apparent activation energies in such systems is a far from simple task. 9,[22][23][24][25][26] Nevertheless, the results obtained here are well correlated with the role played by the increase of temperature and water content in facilitating the electrochemical oxidation of ethanol on platinum in phosphoric acid media. Moreover, the obtained values are in the range of that found for other comparable reaction and the changes with the electrolyte and the temperature range might well reflect the changes in the reaction mechanism.…”

Complex Oscillatory Response of a PEM Fuel Cell Fed with H[sub 2]/CO and Oxygen

“…[1][2][3] Particularly in the case of low temperature fuel cell relevant reactions, such as the catalytic electrooxidation of hydrogen and small organic molecules, oscillatory dynamics seems to be a rule rather than an exception. [4][5][6][7][8][9][10][11] Current and potential oscillations during the electro-oxidation of hydrogen have been very often observed since the first half of the last century. [12][13][14][15][16][17][18][19] The current understanding of this reaction is that oscillations arise due to the overlap between two potential-dependent adsorption isotherms.…”

Potential oscillations during electro-oxidation of ethanol on platinum in alkaline media: The role of surface sites

“…To do this, the applied current was normalized according to the following equation, proposed by Nagao et al [29]:…”