Chemical-Potential-Dependent Thermodynamic Study of Electrochemical Nitric Oxide Reduction to Ammonia on Single-Cluster Catalysts

The chemical potential (μ) is a substantial but ignored factor in many theoretical studies of electrochemical nitric oxide reduction (NORR). Herein, by means of the grand canonical density functional theory in the JDFTx, the chemical-potential-dependent intermediate configurations and catalytic activities have been investigated on the designed nine single-cluster catalysts, which are composed of the trimeric-transition-metal cluster-embedded graphitic carbon nitride (TM3@C3N4, TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu). The Co3@C3N4, Ni3@C3N4, and Cu3@C3N4 with small or even no thermodynamic energy barriers are considered to be efficient NORR catalysts at μ= 0 eV vs SHE. By the analysis of the chemical-potential-dependent density of state (DOS), electron variation, and global softness (S), the intrinsic charge effect induced by the applied chemical potential (μ) has been revealed. We refer to the fact that chemical potential plays an important role in catalytic activity evaluation and electronic property analysis, which cannot be described in the traditional electric neutral model.