Fig. 4: Changes in elemental composition after the electrochemical stress test at various pH.

W/Mo and Sb/Sn atomic ratio evaluated by EDX (black line), and XPS (blue line) for MO, MO@pH2, MO@pH1, and MO@pH0. The Ovac/Olattice ratio (red line) was obtained from the O 1 s high-resolution XPS core-level spectra in Fig. S5. The error bars represent the standard deviation of duplicate samples.