Fig. 2
Correlation with intrinsic HER activity. HER activity trends of overpotential at 10 mA cm−2oxide as a function of a A-site ionic electronegativity, and b A-site ionic radius for single and double perovskites studied here. Plots of Tafel slope values as a function of c A-site ionic electronegativity (the rate-determining steps estimated from the Tafel slope are shown in pink and purple dashed lines), and d A-site ionic radius for the prepared single and double perovskites. Error bars stand for the standard deviation (s.d.) of three independent HER measurements performed in 1.0 M KOH at 25 °C and the gray dashed lines are shown for guidance only. Triangles and squares represent the single and double perovskites, respectively. Sr-doped perovskites (green) and perovskites doped with different lanthanides (Sm0.5La0.5 and Pr0.5Gd0.5 in black) are shown in distinguished colors
