Theoretical studies of non-noble metal single-atom catalyst Ni1/MoS2: Electronic structure and electrocatalytic CO2 reduction

Single-atom catalysts (SACs) have aroused significant interest in heterogeneous catalysis in recent years because of their high catalytic selectivity and tunable activity in various chemical reactions. Herein, non-noble metal SACs with 3d-series metal single atoms (M1) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) supported on MoS2 are computationally screened by using first-principles quantum-chemical theory. The Ni1/MoS2 catalyst is found to be the most stable among those 3d-series SACs due to the optimal binding energy. In order to provide a fundamental understanding of the intrinsic stability and bonding interaction between the metal single atoms and MoS2 support, the electronic structure, including the spin density populations, charge density difference (CDD), electron localization function (ELF), band structure, density of states (DOS), and crystal orbital Hamiltonian populations (COHP) are systematically examined. The solid-state quantum theory of atoms in molecules (QTAIM) is also applied to further characterize the Ni—S and Mo—S covalent and ionic bonding nature between the metal single atoms and support. It is found that in addition to Ni—S bonding, there exists significant Ni—Mo bonding that is critical for the electronic structure, stability, and catalytic properties of Ni1/MoS2 catalyst. As a typical application of this Ni1/MoS2 catalyst, the electrocatalytic mechanism and reaction pathway of CO2 reduction reaction (CO2RR) on Ni1/MoS2 catalyst have been investigated. The MoS2-supported Ni single atoms are found to exhibit high catalytic activity for CO2RR to methanol. The calculational results provide theoretical insights towards the design of highly efficient SACs on MoS2-based functional materials.