Electrolytic cell for hydrogen and sulfuric acid production

The anodic depolarization of sulfur dioxide reduces the thermodynamic potential of water splitting from 1.23 V to 0.29 V at 50 % H2SO4 wt. and temperature of 25 degrees C. This process leads to hydrogen and sulfuric acid production. The major problem of the electrolytic cell is the permeation of SO2 into the cathode compartment where the 'parasitic' reaction of SO2 + 4H(+) -> S + H2O takes place, thus decreasing the hydrogen efficiency and poisoning the cathode catalyst. The original idea, supporting this study, is to use gas diffusion electrodes (GDEs) as anodes, designed to electrochemically oxidize SO2. Carbon GDEs have been developed and modified with cobalt phthalocyanine (CoPc). The GDEs serve as a membrane attenuating SO2 permeation. An electrolytic cell with ODE has been designed and tested with: (i) different types of ODE; (ii) with and without membranes; and (iii) utilizing J(-)J(2) as a mediator. It has been found that when operating with gas mixtures which contain up to 20% vol. SO2, the main issue, namely its permeation into the electrolyte, can be solved. This beneficial approach can be used to treat waste gases with low SO2 concentration which would have a favorable impact on the environment.