Title : Formate electrooxidation using cobalt hexacyanoferrate as non-noble metal catalyst
Abstract:
One of the biggest challenges currently facing humankind and the scientific community is the energy production and consumption without the use of fossil fuels. Big efforts have been invested in creating technologies that enable closed carbon or carbon neutral fuel cycles, decreasing CO2 emissions into the atmosphere. Formic acid/formate (FA) has attracted increasing interest as a liquid fuel over the last half century, giving rise to many studies seeking for efficient catalysts for FA electrocatalytic oxidation in fuel cells. However, the FA oxidation catalysts are typically based on Pt or Pd, which are prone to catalytic deactivation by adsorption of intermediate species (e.g., CO). We propose the use Co−Fe Prussian Blue derivative (CoFePB), which is one of the first heterogeneous noble-metal-free catalysts reported for the electrooxidation of small hydrocarbon molecules. Importantly, the catalyst showed a very high tolerance against surface poisoning during the reaction, as supported by the cyclic voltammetry and electrochemical impedance spectroscopy data. The remarkable selectivity, stability, and high current density of CoFePB, in contrast to state-of-the- art catalysts based on platinum-group metals, open new oportunities in the search for inexpensive earth-abundant materials for oxidation of organic molecules either for use in liquid fuel cells or for selective organic molecule sensors. Focusing on fuel cell applications, although the currently obtained onset potential must be further decreased, CoFePB can be already implemented in a formate fuel cell using a strong enough oxidant, i.e., stronger than oxygen, which is the typically employed oxidant in fuel cells. As a proof-of-concept, an aqueous direct formate fuel cell configuration has been developed using CoFePB as a formic acid oxidation catalyst coupled with carbon felt as a cathode, Ce4+ as oxidant, and anolyte and catholyte solutions working at basic and acidic pH conditions, respectively. With a maximum power output of 8.6 mW cm-2, this is the first example of a fully noble-metal-free direct formate oxidation fuel cell.
