Electrocatalytic Oxidation of Dinitrogen to Nitric Acid via Direct Ten–Electron Transfer Using Manganese Phthalocyanine

Ammonia produced through the energy intensive Haber–Bosch process, undergoes catalytic oxidation for the manufacture of commercial nitric acid in the age–old Ostwald process. This two–step energetically non–viable industrial process demands the quest of an alternative single step electrocatalysis from the last century. The quest ends up in optimism when we unravel a ten–electron pathway associated with electrochemical dinitrogen oxidation reaction (N2OR) to nitric acid by manganese phthalocyanine (MnPc) hierarchical nano–structures (HNs) at STP. The catalyst delivers nitric acid yield of 720 µmol h–1 g–1cat @ 1.9 V vs. RHE and F.E. of 17.32 % @ 1.7 V vs. RHE in 0.05 M HCl. The local co–ordination environment (Mn–N4) during electrocatalysis process is ensured by the XAFS study. DFT based calculations express that the Mn site of MnPc is the main active center for nitrogen adsorption for N2OR, suppressing the OER.