Iron(I) Tetraphenylporphyrin\nIs an Active Catalyst\nin Reductive Deoxygenation when Switching from CO<sub>2</sub> to Isoelectronic\nN<sub>2</sub>O

The electrochemical reductive deoxygenation of N<sub>2</sub>O catalyzed\nby iron tetraphenylporphyrin (TPPFe) is studied and compared to the\nelectroreduction of CO<sub>2</sub> to CO by the same catalyst. We\nshow that the electroreduction of N<sub>2</sub>O is catalyzed by TPPFe(I),\nalbeit at a slower rate compared to that of TPPFe(0). On a similar\ntime scale, CO<sub>2</sub> does not react with TPPFe(I). The catalytic\nreduction of N<sub>2</sub>O by TPPFe(I) is however endowed by a self-modulation\nprocess due to the production of hydroxide ions as a coproduct that\nbind to TPPFe(II) and slow down the regeneration of the TPPFe(I) catalytic\nactive species. Two catalytic cycles are thus intertwined when the\nelectrocatalysis is run at a potential where TPPFe(0) is generated,\nand the resting state in solution is TPPFe(II)(OH) and not TPPFe(I),\nas opposed to the case of CO<sub>2</sub> catalytic reductive deoxygenation.\nRevealing the shift of the active catalysis from TPPFe(0) to TPPFe(I)\nopens the way toward the design of molecular catalysts for N<sub>2</sub>O reductive deoxygenation at a lower overpotential.