▎ 摘　　要

The non-equilibrium Green's function approach is applied to investigate dc Josephson currents in S/ZGNR/S junctions, where ZGNR is the zigzag graphene nanoribbon and S is the s-wave superconductor. If the middle ZGNR is half-metallic ferromagnetic, the supercurrent changes from vanishing to a finite value when the gate voltage is adjusted, exhibiting a supercurrent switching effect.