A bilayer coating as an oxygen-transfer cascade for the electrochemical ambient conversion of methane to oxygenates.

Oxidation of methane at ambient conditions to useful oxygenates at a bilayer-coated electrode is demonstrated. The composition of the coating, a Mn porphyrin mediator layer on top of a N(OH)2/NiOOH one, allows a cascade of oxygen transfer events upon applying a potential. It is shown, using (spectro)electrochemical techniques, density functional theory computations and product analytical methods, that formate and methanol accompanied by CO2 suppression can be observed at a certain potential range. This can lead to further development of similar oxygen/electron transfer cascades for possible use in devices for energy conversion and fuel/product generation.

DFT and Empirical Considerations on Electrocatalytic Water/Carbon Dioxide Reduction by CoTMPyP in Neutral Aqueous Solutions*.

A combined experimental and density functional theory (DFT) investigation was employed in order to examine the mechanism of electrochemical CO2 reduction and H2 formation from water reduction in neutral aqueous solutions. A water soluble cobalt porphyrin, cobalt [5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin], (CoTMPyP), was used as catalyst. The possible attachment of different axial ligands as well as their effect on the electrocatalytic cycles were examined. A cobalt porphyrin hydride is a key intermediate which is generated after the initial reduction of the catalyst. The hydride is involved in the formation of H2 and formate and acts as an indirect proton source for the formation of CO in these H+ -starving conditions. The experimental results are in agreement with the computations and give new insights into electrocatalytic mechanisms involving water soluble metalloporphyrins. We conclude that in addition to the porphyrin's structure and metal ion center, the electrolyte surroundings play a key role in dictating the products of CO2 /H2 O reduction.