RESEARCH / A0233
Rare-Earth-Induced Intermediate-Spin Co Centers in MnCo2O4.5 for Sustainable Acidic Water Oxidation
Read the original paper · 10.1021/jacs.5c17361 ↗
Source figures may contain other techniques and soft X-ray spectra. C, N and O measurements are outside our current hard-XAFS testing range.
Figure 2. Structural characterizations and magnetic properties of Sm-MnCo2O4.5. (a, b) High-resolution XPS spectra of Co 2p and Mn 2p regions for MnCo2O4.5 and Sm-MnCo2O4.5. (c) Quantitative analysis of Co and Mn oxidation states based on XPS peak deconvolution. (d) Co K-edge XANES spectra of Sm-MnCo2O4.5, MnCo2O4.5, Co foil, CoO and Co3O4. (e) Normalized Co XES spectra of the CoO, Co3O4, MnCo2O4.5, Sm- MnCo2O4.5 and Co2O3. (f) Temperature-dependent EPR spectra of Co3O4, MnCo2O4.5, and Sm-MnCo2O4.5 recorded at 100, 150, 200, and 298 K. (g) The magnetization hysteresis loops (M-H curves) at room temperature of Sm-MnCo2O4.5 and MnCo2O4.5. (h) Temperature-dependent magnetic susceptibility under field-cooled (FC) mode at 1000 Oe. (i) Schematic illustration of Co spin-state transition from high-spin (HS) to intermediate-spin (IS) induced by Sm doping.
Figure 4. Valence state, electronic and structural evolution of MnCo2O4.5 and Sm-MnCo2O4.5 during acidic OER. (a, b) Co K-edge XANES spectra of MnCo2O4.5 and Sm-MnCo2O4.5 collected under different applied potentials. (c) The oxidation states of Co versus potential. (d, e) Fouriertransformed Co K-edge EXAFS spectra and (f) corresponding fitted Co−O coordination. (g) In-situ Raman spectra of Sm-MnCo2O4.5 under increasing potential. (h) Schematic illustration of the local coordination and electronic structure transformation from Co−O−Mn to Co−O−Sm.