fig8

Figure 8. (A) Tafel plots, (B) the ECSA, and (C) EIS of the N,P-3D-GA, MnZn/N,P-3D-GA, Zn/N,P-3D-GA and Mn/N,P-3D-GA; and (D) the stability of MnZn/N,P-3D-GA at -0.92 V (vs. RHE). ECSA: Electrochemical active surface area; EIS: electrochemical impedance spectroscopy; 3D: three-dimensional; GA: graphene aerogel; RHE: reversible hydrogen electrode.