Selective electro-oxidation of renewable diols in OrganoMetallic Fuel Cells (OMFCs) for both energy and chemicals production

Direct alcohol fuel cells (DAFCs) operating in alkaline environment are the only devices where the free energy of an alcohol can be converted into electrical energy with contemporaneous release of a higher added-value product. A crucial role for achieving this goal is played by the anode electrocatalyst that must promote the partial oxidation of the alcohol to carboxylic compounds in a selective way and with fast kinetics. This sustainable chemistry goal has been attempted for many years, with limited success: palladium nanoparticle based catalysts can oxidize selectively ethanol to acetate but fail in selective polyalcohols oxidation. A solution comes from an innovative kind of DAFC, developed in the last few years: OrganoMetallic Fuel Cells (OMFCs), which employ, as anodic electrocatalysts, organometallic compounds. The established methods for organometallic synthesis, leading to well-defined molecular metal complexes, offer enormous advantages in the rational design and optimization of fuel cell catalysts, so organometallic catalysts can allow selective fuel oxidation. In addition, these catalysts employ low metal loading respect nanostructured catalysts, due to the fact that a high number of metal sites could be active. We have employed the rhodium complex [Rh(OTf)(trop2NH)(PPh3)], supported on Ktejen Black®, as anodic electrocatalyst in DAFCs for oxidation of renewable diols like ethanol, ethylene glycol and 1,2-propanediol. These alcohols are selectively oxidized to the carboxylic compounds as described in Figure 1. This organometallic catalyst, which is the first metal complex ever used as anodic electrocatalyst in a fuel cell, matches the goal of both energy and raw chemicals production in DAFCs