Sustainable Electrochemical Synthesis of Large Grain- or Catalyst-Sized Iron

Abstract

Electrolytic production of iron in molten salts by splitting iron oxide into iron metal and O2 is a low-carbon footprint alternative to the massive CO2 emissions associated with conventional carbothermal iron production and permits. This study advances a CO2-free method for iron production, by modifying iron electrosynthesis in molten Li2CO3 to control iron product particle size and by decreasing the electrolyte extracted with the pure iron product. We present the first study of electrolytic iron micro-morphology as formed from iron, and demonstrate it is strongly influenced by the deposition conditions. Particle size and morphology are critical characteristics in a variety of metal applications. In this study, large (~500 µm) iron particles are formed at low current densities during extended electrolysis, or at high Fe(III) concentrations, and small (~10 µm) at high current density and low Fe(III). Deposited Fe is fiber shaped from equal molals of Fe2O3 and Li2O, but particle-like from electrolytes with surplus Li2O. Iron is formed at high current efficiency, and the observed electrolysis potential decreases with (i) the decreasing current density, (ii) addition of Li2O, (iii) the increasing anode area, and (iv) the increasing temperature.