Electrochemical Reduction of N <sub>2</sub> O with a Molecular Copper Catalyst
Jorge L. Martinez, Joseph E. Schneider, Sophie W. Anferov, John S. Anderson
Abstract
High Resolution Image Download MS PowerPoint Slide Deoxygenation of nitrous oxide (N 2 O) has significant environmental implications, as it is not only a potent greenhouse gas but is also the main substance responsible for the depletion of ozone in the stratosphere. This has spurred significant interest in molecular complexes that mediate N 2 O deoxygenation. Natural N 2 O reduction occurs via a Cu cofactor, but there is a notable dearth of synthetic molecular Cu catalysts for this process. In this work, we report a selective molecular Cu catalyst for the electrochemical reduction of N 2 O to N 2 using H 2 O as the proton source. Cyclic voltammograms show that increasing the H 2 O concentration facilitates the deoxygenation of N 2 O, and control experiments with a Zn(II) analogue verify an essential role for Cu. Theory and spectroscopy support metal–ligand cooperative catalysis between Cu(I) and a reduced tetraimidazolyl-substituted radical pyridine ligand (MeIm 4 P 2 Py = 2,6-(bis(bis-2- N -methylimidazolyl)phosphino)pyridine), which can be observed by Electron Paramagnetic Resonance (EPR) spectroscopy. Comparison with biological processes suggests a common theme of supporting electron transfer moieties in enabling Cu-mediated N 2 O reduction.