Fig. 3: Identifications of ultimate active sites toward OER.
From: Lattice oxygen activation enabled by high-valence metal sites for enhanced water oxidation
a Steady CV scanning curves of electrochemical activated MCA films. b Electrochemical in situ Raman spectra of EA-FCCN at the range of 350–700 cm−1 at the operated potentials from 1.1 to 1.5 V versus RHE. cδ(Ni-O)-to-ν(Ni-O) ratios in electrochemical in situ Raman spectra of various catalysts related to the operated potentials. d, e Ex situ sXAS measurements of various catalysts. d Ni L-edge and (e) O K-edge sXAS spectra. Dash and solid lines represent the spectrums collected at open circuit condition and the operated potentials (i.e., 1.5 V for EA-FCCN, 1.55 V for EA-FCN, and 1.6 V for EA-CCN), respectively. f Schematic representation of activating oxygen ligands induced by Ni4+ species in Mott-Hubbard model. g Computational 3d-orbitals PDOS diagrams of localized Ni site adjacent to Fe/Co in various oxyhydroxide models, together with the related band centers.
