The vast amount of carbon dioxide reduction research from investigations over many years has resulted in the discovery and characterization of numerous catalysts that can reduce CO2 to CO or formate. However, very few of these can convert CO to more valuable or multi-carbon products such as methane, ethanol, and acetone. The few that have emerged are largely based on metallic copper electroreduction. Writing in the Journal of Physical Chemistry C, Sangyeon Lee and co-workers at Rensselaer Polytechnic Institute highlight a naturally occurring iron compound, called green rust (GR), as another potent reductant capable of converting CO selectively to acetone.

The team synthesized both powdered GR and a thin film grown on an iron chip in order to carefully study its behaviour in the presence of CO. The powder was synthesized from white rust by the general description outlined above, and the thin film was electrodeposited onto the chip with 50 cycles between –1 and –0.2 V in 0.5 M NaHCO3 at pH 9.5, saturated with N2. The team used the powder to carry out the reduction of CO, with nuclear magnetic resonance spectroscopy to determine the product distribution in solution and Raman spectroscopy to characterize the resulting iron product. The thin film was used to analyse the band structure and electronic properties of GR using electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis.