Controlling the Metal–Ligand Coordination Environment of Manganese Phthalocyanine in 1D–2D Heterostructure for Enhancing Nitrate Reduction to Ammonia

Abstract

Eight-electron nitrate reduction (NO3RR) offers a cost-effective and environmentally friendly route of ammonia production and wastewater remediation. However, identification and reinforcement of the metal–ligand interaction responsible for the catalytic activity in transition-metal phthalocyanine-based heterostructures still remain unclear due to their complexity. Herein, directed by computation, we present a heterostructure approach to couple 2D graphene sheets with 1D manganese (II) phthalocyanine to produce a pyrrolic-N coordinated electron-deficient Mn center that interacts to generate the vital intermediates of the NO3RR process. The catalyst system delivers an ammonia yield rate of 20,316 μg h–1 mgcat–1, a faradaic efficiency (FE) of 98.3%, and an electrocatalytic stability of 50 h. Mechanistic investigations verified by FTIR spectroscopy and theoretical calculations to identify Mn coordinated pyrrolic-N as the active sites in MnPc and RGO reinforce the active sites by orbital interaction for enhancing the charge transfer in the formation of *NOH @ NO3RR intermediates while suppressing the competitive hydrogen evolution reaction (HER), resulting in high selectivity and FE.