Influence of particle size on the apparent electrocatalytic activity of LiMn₂O₄ for oxygen evolution

Abstract

Particle size influences the product current densities of LiMn2O4 where smaller particles showed higher faradic efficiency for the OER.

Undesired Bulk Oxidation of LiMn2O4 Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes

“…Our previous studies showed no evidence of morphological changes of the LiMn 2 O 4 nanoparticles in NaOH). [5,6] As the detected Mn loss during the first 5 cycles is similar for all LiOH electrolytes ( Figure S1) and also similar to the Mn loss reported in NaOH, [5] we expect that no changes in morphology occurred in the used LiOH electrolytes. In Figure 2a, the anodic and cathodic traces of the CV in NaOH were featureless except for the exponential rise due to oxygen evolution, [4][5] while there was a clear anodic shoulder and cathodic peak in the CV in LiOH.…”

“…We investigated the CV of 10 mM LiOH further as it showed a clear exponential rise in current density and emphasized the aforementioned differences to previous studies in NaOH and KOH (Figure c). The rising disk current density at high voltage was assigned based on the ring current (blue dashed line), which was set to reduce oxygen at 0.4 V vs. RHE and thus qualitatively detected the oxygen produced at the disk.…”

“…This procedure reduces a possible contamination of the electrodes. A RHE (Hydroflex, Gaskatel GmbH) was used to calibrate the SCE to RHE scale . For XAS measurements we used graphite foil (Alfa Aesar 99.8 %) as the electrode instead of a glassy carbon in the RRDE‐setup.…”

“…For RRDE‐measurements, we used a rotation speed of 1600 rpm. The detection potential for the detection of oxygen was determined in our previous work . Our protocol includes an impedance measurement from 100 KHz to 1 Hz at the open circuit potential.…”

“…The detection potential for the detection of oxygen was determined in our previous work. [6] Our protocol includes an impedance measurement from 100 KHz to 1 Hz at the open circuit potential. The ohmic resistance for the iR correction was obtained from this measurement at high frequency where the phase angle approached zero.…”