Effect of the anode composition on the performance of reversible chlor-alkali electro-absorption cells

In this work, the performances of a reversible electrochemical cell for the storage of energy using the chloralkaline process was investigated. The cell operates at room temperature with liquid electrolytes in both compartments. In the electrolyzer mode, the cell transforms a sodium chloride solution into hydrogen and chlorine, which is then disproportionated to form hypochlorous acid and hypochlorite. In fuel cell operation mode, the cell becomes an electro-absorber to oxidize hydrogen at the anode while reducing hypochlorous acid at the cathode. Because of the low solubility of hydrogen, a special mechanical device is used to produce hydrogen microbubbles in the anodic compartment. The influence of the ratio Ru/Pt in the electrode devoted to the electrochemistry of chlorine species is also evaluated. It was found that a molar ratio Ru:Pt in the range 3-4 was good enough to obtain a good performance in both operation modes (electrolyzer and fuel cell). In the electrode in charge of the hydrogen electrochemistry a platinum coating on Ti was used and it demonstrates robustness enough to obtain good operation results. Maximum efficiency in the electrolysis mode was 8.0 mmol H-2/Wh while in the fuel cell mode, the maximum energy production reached 0.5 Wh/mol H-2.