Local Modulation of Single-Atomic Mn Sites for Enhanced Ambient Ammonia Electrosynthesis

Rationally tuning the local structures of single-atomic active sites for the electrocatalytic N2 reduction reaction (NRR) remains an urgent but worthwhile research topic. Herein, we accomplish the local modulation of single-atomic Mn sites and construct single Mn-O3N1 sites anchored on porous carbon (Mn-O3N1/PC) by delicately controlling the Mn-O bonding conditions. The constructed structures are confirmed via the combination of atomic-scale imaging, Raman spectroscopy, synchrotron radiation-based soft and hard X-ray absorption spectroscopies, and X-ray photoelectron spectroscopy. The Mn-O3N1/PC catalyst yields an NH3 yield rate of 66.41 μg h-1 mgcat.-1 (corresponding to 1.56 mg h-1 mgMn-1) at -0.35 V versus reversible hydrogen electrode, which is about four times that on the control Mn-N4/PC catalyst. The enhanced NRR performance is ascribed to its unique geometry and electronic structures, which not only facilitate the adsorption and activation of the N2 molecule but also lower the free energy change of the potential-determining step.