Cobalt(II) Hematoporphyrin IX immobilized in a cellulose acetate niobium(V) oxide composite membrane: preparation and oxygen reduction study

hematoporphyrin ix [8,13,-bis(1-hydroxyethyl)-3,7,12,17-tetramethyl-21h-porphyrin-2,18-dipropionic acid] was adsorbed on the organic-inorganic composite membrane cel/nb2o5 surface. the porphyrin is strongly adhered on the nb2o5 surface by reaction of the porphyrin co2h groups with nb2o5 forming the -coo-nb chemical bond. metallation of the porphyrine ring was made very easily by immersing the membrane in co(ii) solution and allowing to rest for a few hours. the electronic absorption bands due to the q bands indicated the symmetry change from d2h to d4h upon metallation of the porphyrin ring. the chemical analyses of the material confirmed that the metallation yield was practically 100%. oxygen was reduced on a electrode surface made with the material under a cathodic peak potential of -390 mv, in 1 m kcl solution at ph 1, temperature of 298 k and at ambient pressure. the oxygen reduction was proposed to occur by a two electron transfer mechanism. a linear cathodic peak current response was obtained for dissolved oxygen concentrations between 1.5 and 15 ppm.