To identify the distinction between the active phase formation and valence state of surface metals of two catalysts, we furthermore performed XPS characterization. XPS full spectra of respectively. Compared with CoNiCuFe-Oxide, Co peaks in the spectra of CoNiCuFe-PBA have obvious red shift (Figure ), which manifests that there were higher valence Co cations in CoNiCuFe-PBA, and this would make it easy to be hydrated and adsorb oxygenated intermediate species in the electrocatalysis process to reconstruct into CoOOH active phase. Similarly, the Ni element in CoNiCuFe-PBA has a higher oxidation state than CoNiCuFe-Oxide (Ni 2p spectra in Figure ), which could cooperatively form NiOOH at a low overpotential to enable a higher OER activity. The peaks centered at 856.6 and 858.15 eV of CoNiCuFe-PBA correspond to Ni 2+ and Ni 3+ , while those shifts to lower binding energies at 852.8 and 853.7 eV of CoNiCuFe-Oxide (Figure ) . In addition, Cu cations mainly exist in the form of Cu 2+ for both catalysts (Figure ), but similarly display a completely positive shift of CoNiCuFe-PBA. At the initial stage of the OER, there is a competition for electron donation between oxygen anions and the redox process of metal cations on the catalyst surface. The higher extent of the initial valence state of Co or Ni cations, the more electrons are distributed to the electronic orbital of O, which is more favorable to oxygen evolution. Therefore, XPS results testify that there are more high-valence state of Ni and Co elements in the CoNiCuFe-PBA than the CoNiCuFe-Oxide (Figure ), so it can eliminate most of the metal oxidation process and accelerate the active phase transformation, thereby rendering a higher catalytic activity of OER. The O 1s XPS spectra of the two catalysts further confirmed the above points. As can be seen from Figure , the peaks at 529.6, 531.3, and 532.9 eV are assigned to the metal-oxygen (M-O), hydroxyl groups (O-H), and hydrated surface adsorbed H2O of CoNiCuFe-oxide, respectively. Nevertheless, there exists few signals of M-O in CoNiCuFe-PBA and the peak of O-H shifted positively to 531.3 eV. The more O-H hydroxide and absorbed H2O(l) bonds but fewer M-O bonds indicate the stronger binding strength with active intermediates and the higher degree of hydroxylation of CoNiCuFe-PBA. It is worth noting that the CoNiCuFe-PBA with good crystallinity adsorbs more H2O and *OH, which is consistent with its stronger metal redox activity and thus higher OER activity. This suggests that crystallinity and orderliness may not be a universal "descriptor" of activity for all OER catalysts, but more for oxide OER catalysts. On the contrary, the ability to combine *OH and then hydroxylate, i.e. the ability to form an active phase, is the intrinsic determinant of high catalytic activity.