fig6

Figure 6. High-resolution XPS spectra of (A-C) Pt 4f for PtCo–S/MCS, PtFe–S/MCS and PtCu–S/MCS catalysts; (D) Co 2p for PtCo–S/MCS, (E) Fe 2p for PtFe–S/MCS, (F) Cu 2p for PtCu–S/MCS; (G-I) S 2p for PtCo–S/MCS, PtFe–S/MCS and PtCu–S/MCS catalysts. MCS: Mesoporous carbon nanospheres; XPS: X-ray photoelectron spectroscopy.