Galvanostatic response, oxidation rates

Figure 11. Transient galvanostatic response of the rates of ethylene oxidation r, (O) and deep oxidation rt (0) and of the cell overvoltage AV for reactor RC 9. Electrolyte breakdown occurred at 40 min. Conditions RC 9, 420°C, i — 100 pA, P0l = 0.095 bar, PET = 0.012 bar.

The nature and structure of surface intermediates in hydrocarbon adsorption has been investigated using galvanostatic (constant current) and potential sweep techniques (7, 10, 172-174 or radiotracer methods (175. Niedrach s (172, 173 galvanostatic results with C1-C4 alkanes and with ethylene indicate the existence of common, partially oxidized surface species, despite differences in the initially adsorbed hydrocarbons. Methane adsorption is very slow, but higher saturated hydrocarbons adsorb faster and at similar rates. Potentiostatic adsorption followed by an anodic potential sweep gives two peaks [Fig. 14 (174 corresponding to different adsorbed species. The intermediate responsible for the peak at low potentials (0.7-... 

Figure 18 depicts a galvanostatic transient experiment, showing the rate response to an applied current step (+300 aA for 120 min) during ethylene oxidation on an Ir02 catalyst/ The evolution of the catalyst film potential with respect to the reference electrode, Kwr, is also given. Initially the circuit is open (/ = 0) and the unpromoted catalytic rate is very slow. At f = 0 a constant current (/ = +300 tA) is applied between... 

---