Undesired Bulk Oxidation of LiMn₂ O₄ Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes.

ABSTRACT: Chemical and structural changes preceding electrocatalysis obfuscate the nature of the active state of electrocatalysts for the oxygen evolution reaction (OER), which calls for model systems to gain systematic insight. We investigated the effect of bulk oxidation on the overpotential of ink-casted LiMn₂ O₄ electrodes by a rotating ring-disk electrode (RRDE) setup and X-ray absorption spectroscopy (XAS) at the K shell core level of manganese ions (Mn-K edge). The cyclic voltammogram of the RRDE disk shows pronounced redox peaks in lithium hydroxide electrolytes with pH between 12 and 13.5, which we assign to bulk manganese redox based on XAS. The onset of the OER is pH-dependent on the scale of the reversible hydrogen electrode (RHE) with a Nernst slope of -40(4) mV/pH

SUBMITTER: Baumung M 

PROVIDER: S-EPMC6899966 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature