Experimental correlation of Mn³⁺cation defects and electrocatalytic activity of α-MnO₂– an X-ray photoelectron spectroscopy study

Abstract

Identification and exploration of catalytically active sites is key to designing and engineering low-cost and earth-abundant highly active electrocatalyst materials as alternative to Pt/C in a variety of electrochemical energy...

Boosting the Stability of Highly Flexible Cathodes in Zinc‐Ion Batteries via the Pillaring Effect of Molybdenum in α‐MnO2

“…[38,39] The three split peaks in the O 1s spectra (Figure 2f) indicate metal-oxygen bond in the lattice (529.7 eV), oxygen vacancy (531.4 eV) and adsorbed water (532.5 eV). [40,41] Subsequently, Raman spectroscopy (Figure S7) indicates stretching vibrations, including the F 2g vibrational mode (514 cm À 1 ) and the A g vibrational mode (579 and 636 cm À 1 ), as well as bending vibrations (399 cm À 1 ) and antisymmetric stretching vibrations (739 cm À 1 ) of MnÀ O bonds in MnO 6 octahedra in the CC@MMO band. [42] Distinctly, in the CC@MnO 2 pattern, only the primary peak at 658 cm À 1 and two secondary peaks at 319 and 371 cm À 1 are attributed to the MnÀ O bond.…”

“…The Mn 2p spectrum (Figure 2e) reveals that the Mn element comprises two valence states, Mn 3+ (642.2 eV and 653.6 eV) and Mn 4+ (643.7 eV and 654.4 eV), with a binding energy separation of 11.6 eV between Mn 2p 3/2 (642.4 eV) and Mn 2p 1/2 (654.0 eV) orbitals [38,39] . The three split peaks in the O 1s spectra (Figure 2f) indicate metal‐oxygen bond in the lattice (529.7 eV), oxygen vacancy (531.4 eV) and adsorbed water (532.5 eV) [40,41] . Subsequently, Raman spectroscopy (Figure S7) indicates stretching vibrations, including the F 2g vibrational mode (514 cm −1 ) and the A g vibrational mode (579 and 636 cm −1 ), as well as bending vibrations (399 cm −1 ) and antisymmetric stretching vibrations (739 cm −1 ) of Mn−O bonds in MnO 6 octahedra in the CC@MMO band [42] .…”

Effects from Surface Structures of Manganese Phosphate on Electrocatalytic Water Oxidation

“…The Mn 2p spectra show similar main and satellite peaks (Figure h), and the Mn 3s spectra also show similar peak positions (Figure i). These results indicate that the valence states of Mn in both MnPi electrocatalysts are divalent . The XPS spectra of P, O, and Na elements in both MnPi electrocatalysts are displayed in Figure S1.…”

“…These results indicate that the valence states of Mn in both MnPi electrocatalysts are divalent. 24 The XPS spectra of P, O, and Na elements in both MnPi electrocatalysts are displayed in Figure S1. High-resolution transmission electron microscopy (HR-TEM) further showed identical structures (Figure S2).…”

Design of a flexible but robust setup for temperature‐dependent electrochemistry down to cryogenic temperatures

“…The assembled cryo-electrochemical cell setup with all external connections is illustrated in Figure 4 (please find detailed descriptions on preparatory procedures and the assembly in SI section S3 [50,51]). It was field-tested with the Ferrocene j Ferrocenium (Fc j Fc + ) redox couple (eqn.…”