▎ 摘　　要

The maximized atomic efficiency of supported catalysts is highly desired in heterogeneous catalysis. Therefore, the design and development of active, stable, and atomic metal-based catalysts remains a formidable challenge. To tackle these problems, it is necessary to investigate the interaction between single atoms and supports. Theoretical calculations indicate that the Pd binding strength is higher on graphene/amorphous carbon (AC) than that on graphene or AC substrate. Based on these predictions, we present a facile confined-interface-directed synthesis route for the preparation of single-atom catalysts (SACs) in which Pd atoms are well-dispersed on the interface of double-shelled hollow carbon nanospheres with reduced graphene oxide (RGO) as the inner shell and AC as the outer shell. Owing to the synergetic effect of the RGO/AC confined interface and the atomically dispersed Pd, the as-made RGO@AC/Pd SAC achieves the maximum atomic efficiency (catalytic activity) of Pd species and exhibits an excellent stability in chemical catalysis. This confined-interface-directed synthesis method provides a novel direction to maximize the atomic efficiency, improve the activity, and enhance the stability of metal-based catalysts.