“…The XPS spectrum in Figure a reveals the existence of Ni, Co, O, and P in the NiCo 2 O 4 /Ni 2 P composite catalyst. As shown in Figure b, the Ni 2p 3/2 spectrum shows four peaks with binding energies of 853.0, 855.6, 856.8, and 861.4 eV, which should be related to the Ni‐P, Ni 2+ , Ni 3+ , and the satellite peak, respectively . Notice that the binding energy of 853.0 eV is very close to that of metal Ni, which suggests the existence of partially reduced Ni species .…”