Monitoring of ethanol electrooxidation on highly efficient conductive RuNi metal-organic framework by mass spectrometry

Ethanol is one of the most promising sustainable fuels for use in direct alcohol fuel cells. The detailed mechanism of the ethanol oxidation reaction (EOR) is still elusive and contradictory. Therefore, developing new materials is critical to achieve an efficient ethanol electro-oxidation. In this work, the catalytic activity of conductive RuNiMOF has been studied and compared to Ni-MOF towards EOR in alkaline medium. Differential electrochemical mass spectrometry (DEMS) has been used for in-situ monitoring the EOR products. Specifically, spectrometric signals of volatile molecules during ethanol oxidation evidenced the production of acetaldehyde as the sole electrooxidation product at both catalysts. It has been also proved that the incorporation of Ru (1.3 at. %) into the Ni-MOF significantly increases the catalytic activity during the ethanol-to-acetaldehyde (CH3CHO) reaction pathway. DEMS has been shown to provide unique information for the study of these reactions, allowing us to propose a mechanism for the entire process. In this sense, this in-situ technique revealed an increment in the amount of oxygen generated during the anodic scan as the ethanol concentration increases. This effect could be related to the formation of NiO during the EOR, which boosts the lattice-oxygen-mediated component of the oxygen evolution reaction.