Surface complexation site type topology determines face-specific electrostatic potentials on single crystal hematite surfaces in aqueous solutions.  Potentiometric titrations of (001), (012), and (113) faces indicate that biases of ~100 mV exist between separated hematite faces immersed in the same cell. When electrically connected these potentials drive currents of  ~10 mA through the circuit using multiple conduction pathways.  Oxalate and Fe(II) bearing solutions were used to study the interplay between surface site complexation, electron transfer reactions, and current flow across these interfaces and through the hematite bulk in various electrolytes.  Conditions that switch on net conduction involving coupled Fe exchange redox reactions were isolated.  However, current flow for coupled water oxidation/reduction reactions at opposing interfaces is generally higher, with no Fe atom exchange nor detectable surface modification.  Combined experiment and modeling are being used to develop a comprehensive quantitative model for chemistry and structure based electrical conduction in this system.

Electron transfer between single crystal hematite/electrolyte interfaces

245th National Meeting (2013)

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