Manipulating Coordination Structures of Mixed-Valence Copper Single Atoms on 1T-MoS2 for Efficient Hydrogen Evolution

Directing single atoms (SAs) to occupy specific lattice sites in support materials and correlating the resulting changes in atomic coordination structures to catalytic activity are crucial for the rational design of high-performance single-atom catalysts (SACs). Herein, for the same copper (Cu) SAs, two coordination structures on 1T-phase molybdenum disulfide (MoS2) are identified. In the adsorption model, Cu SAs are coordinated onto the outermost sulfur (S) plane in a trigonal pyramidal geometry (Cuads@MoS2), while in the substitution model, Cu SAs are substituted with molybdenum (Mo) atoms (Cusub@MoS2), octahedrally coordinating with six S atoms in 1T-MoS2. Interestingly, in both coordination models, Cu(I) and Cu(II) SAs simultaneously exist. Cuads@MoS2 (173 mV) and Cusub@MoS2 (160 mV) demonstrate significantly reduced overpotential (at 10 mA cm–2) for the hydrogen evolution reaction (HER) compared to that of 1T-MoS2 (235 mV) under acidic condition (0.5 M H2SO4). Additionally, theoretical results reveal that different coordination structures would result in distinct active sites, where in Cuads@MoS2, the Cu SAs are the active sites, whereas in Cusub@MoS2, the S atoms most adjacent to the Cu SAs are the major active sites. Accurately determining the atomic coordination structures of SAs and uncovering their structure–property relationships are essential to guiding future geometry and structural research on SACs.