We have studied the oxidation of magnetite to Fe 2O 3 in an electrolytic cell in which the anode is magnetite and the cathode is platinum. We report cyclic voltammagram data consistent with the hypothesis that magnetite, without oxygen gas production but with hydrogen gas production at the cathode, is occurring. The reaction occurs at a potential at the anode of about 0.3 V vs SCE in 1 M NaOH electrolyte, consistent with colloid experiments which also estimated the equilibrium potential of the hypothesized reaction. Electrode characterization results using BET, XEDS, and macroscopic volume and mass measurements are reported, as well as the measurements of the amount of hydrogen gas generated per unit current. The quantity of gas generated is also consistent with our hypothesis concerning the electrode chemistry. Some samples exhibit evidence of two oxidation reactions occurring at the anode and a possible interpretation of these is also discussed. These results suggest the use of magnetite as an anode in a cell electrolysing water to produce hydrogen gas and Fe 2O 3. In such an electrolyser, the electrical energy cost of producing hydrogen gas could be significantly lower than the cost in a standard electrolyser. The measured steady state currents, equivalent to about 400 mA/g of magnetite, are too low to make a practical electrolyser. We briefly discuss several ways in which the currents might be increased to the levels required.
Bibliographical noteFunding Information:
This work was supported by a grant from the Center for Urban and Regional Affairs at the University of Minnesota and by the University of Minnesota Supercomputing Institute. We are extremely grateful to Professor William Smyrl for allowing the use of his laboratory for this investigation and for frequent advice and counsel. We are grateful for the assistance of Research Experiences for Teachers interns Eric Kehoe and Jeremy Kersten and undergraduate assistants Noah Trebesch and Heather Blundell in this work.