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 O 2 is a low-carbon footprint alternative to the massive CO 2 emissions associated with conventional carbothermal iron production and permits. This study advances a CO 2 -free method for iron production, by modifying iron electrosynthesis in molten Li 2 CO 3 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 Fe 2 O 3 and Li 2 O, but particle-like from electrolytes with surplus Li 2 O. Iron is formed at high current efficiency, and the observed electrolysis potential decreases with (i) the decreasing current density, (ii) addition of Li 2 O, (iii) the increasing anode area, and (iv) the increasing temperature.