Journal of Physical Chemistry A, Vol.102, No.43, 8355-8361, 1998
Amplitude control of chemical waves in catalytic membranes. Asymmetric wave propagation between zones loaded with different catalyst concentrations
Chemical waves of the Belousov-Zhabotinsky type are studied applying bathoferroin catalyst fixed on a polysulfone membrane. A new method is developed to create contacting high- (H) and low-amplitude (L) regions for chemical waves. The amplitude is high in zones (H) loaded with high catalyst concentrations, and it is low in zones (L) loaded with low catalyst concentrations. An asymmetric wave propagation is found : waves coming from region H can initiate waves in region L across the HL boundary with a higher frequency than vice versa. The ratio of the cross-recovery times R(L --> H) and R(H --> L) is 1.7 in the experiments reported here. To measure this ratio, rotating chemical waves were applied. The waves propagate in two concentric annular zones-the inner zone with low and the outer with high catalyst concentration-and the HL. boundary forms a circle. It was found that in such a reactor complex wave patterns (so-called chemical pinwheels) can rotate nearly independently in the H and L zones, interacting only weakly across the HL boundary.