fig3

Figure 3. High-resolution XPS spectra of (A) P 2p, (B) Fe 2p, (C) Co 2p, (D) Ni 2p of Fe₃₀Co₃₀Ni₃₀-PNC sample; (E) N₂ adsorption/desorption isotherms and (F) the corresponding pore size distributions of the Fe₃₀Co₃₀Ni₃₀-PNC and Fe₃₀Co₃₀Ni₃₀-NC. XPS: X-ray photoelectron spectroscopy; PNC: phosphorus and nitrogen doped carbon.