Fig. 3: Generation of H3O+-rich micro-environment.
From: Alkaline-based aqueous sodium-ion batteries for large-scale energy storage
a ATR-FTIR spectra for pure carbon and Ni/C at different potentials. Fundamental excitations of H3O+, denoted \({{{{{{\rm{\nu }}}}}}}_{{{{{{{\rm{H}}}}}}}_{3}{{{{{{\rm{O}}}}}}}^{+}}^{{{{{{\rm{u}}}}}}}\) (umbrella vibration), \({{{{{{\rm{\nu }}}}}}}_{{{{{{{\rm{H}}}}}}}_{3}{{{{{{\rm{O}}}}}}}^{+}}^{{{{{{{\rm{a}}}}}}}^{1}}\) (asymmetric O-H stretching), and resonance states between fundamental excitation of asymmetric O-H stretching and combination tones (r + u) denoted \({{{{{{\rm{\nu }}}}}}}_{{{{{{{\rm{H}}}}}}}_{3}{{{{{{\rm{O}}}}}}}^{+}}^{{{{{{{\rm{a}}}}}}}^{2},\,{{{{{\rm{r}}}}}}+{{{{{\rm{u}}}}}}}\), where r and u represent, respectively, frustrated rotation and umbrella vibration. Bending of H2O is denoted \({{{{{{\rm{\nu }}}}}}}_{{{{{{{\rm{H}}}}}}}_{2}{{{{{{\rm{O}}}}}}}^{}}^{{{{{{\rm{b}}}}}}}\). b Operando DEMS findings to determine H2 and O2 evolution during NMF//NTP battery cycling at 0.5 to 2.2 V at 0.5 C. c Schematic for H3O+ accumulation mechanism on electrode surface coated with Ni/C in the alkaline electrolyte.
