Dissolved O2 sensor based on cobalt(II) phthalocyanine immobilized in situ on electrically conducting carbon ceramic mesoporous SiO2/C material

This work describes the preparation of mesoporous carbon ceramics SiO2/50 wt.% C (SBET = 170 m2 g−1), where C is graphite, by the sol–gel method. This material was used as a matrix to support cobalt phthalocyanine (CoPc), prepared in situ on their surface, to assure homogeneous dispersion of the electrocatalyst complex in the pores of the matrix. Pressed disk electrode made with SiO2/C/CoPc was used to analyze dissolved oxygen in water by an electrochemical technique in neutral media and dissolved O2 was reduced at −0.23 V. The linear response range, sensitivity and detection limit obtained were 0.5–6.6 mg L−1, 2.16 μA L mg−1 and 0.01 mg L−1, respectively, by chronoamperometry. A mechanism involving two electrons in O2 reduction was determined by cyclic voltammetry technique. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation was 1.6% for 10 measurements of a solution of 6.5 mg L−1 oxygen. The sensor was applied to determine oxygen in pond and tap water samples showing to be a promising tool for this purpose.