Alloying effects on inhibiting hydrogen evolution of Zn metal anode in rechargeable aqueous batteries

Alloying strategy is a feasible avenue to inhabiting the hydrogen reaction evolution (HER) of Zn anode. However, the general rule to select doping element is still unclear. In this study, the effects of Sn, Bi, Ag, and Co alloying on HER of Zn anode were investigated by experiments and DFT calculations. It is found that the doping of Sn or Bi is beneficial for inhabiting the HER compared with that of Ag or Co doping. The Gibbs free energy change (Delta GH*) and Zn atom binding energy calculations confirm that both Sn and Bi doping can inhabit the HER and dendrite formation. The Bader charge analyses indicate that Sn and Bi gain trivial electrons from neighbor Zn atoms. Bond length calculations show that the Sn and Bi will introduce local distortion into surrounding Zn atoms. The effects of alloying doping on the work functions of Zn anodes indicate that the Sn doping and Bi doping both have lower work functions than those of doping Ag and Co doping. Thus, it is proposed that the elemental doping with less charge transfer, inducing large local distortion and reducing the work function might be beneficial to inhabiting HER of Zn anode.