Frontier Band Orbitals of Active Sites in Single-Atom Catalysis

Active sites in single-atom catalysis are characterized by individual metal atom centers, so their frontier orbitals are often described by the atomic orbital model, but that model is oversimplified and even disputed. We propose a frontier band orbital model to accurately describe the nature of the frontier orbitals of active sites by designing an electronically tunable single-atom catalysis system. The electron distributions at the silver frontier orbitals are tailored by modulating the catalyst's energy bands via adjusting support MnO2 tunnel ions. By transferring partial Ag 4d5s charge to 5p orbitals, Ag1@MnO2 with tunnel potassium ions exhibits more effective adsorption behavior and higher surface reactivity, and hence, it shows a better CO oxidation activity than Ag1/MnO2 without tunnel ions. The band-induced orbital-dependent activity reveals that the frontier orbitals of the active sites not only are the concrete atomic orbitals to dictate adsorption behavior but also bear the delocalized band feature to regulate surface reactivity.