Oxygen Evolution Reaction on an Fe–N–C Catalyst Model in Water-in-Salt Electrolytes

Abstract

The oxygen evolution reaction (OER) is one of the core reactions in energy conversion processes. OER requires further investigations to overcome its high overvoltage (η) problem. A promising catalytic activity of carbonaceous materials doped with Fe and N (Fe−N−C catalysts) has been reported. Recently, a low-η OER phenomenon was observed on step-edge enriched Fe−N−C catalysts in diluted alkaline electrolytes. In this study, the low-η OER was investigated using an Fe−N−C model surface with elongated step edges in an extreme opposite environment, i.e., highly concentrated metal trifluoromethanesulfonates as water-in-salt electrolytes (WiSEs). The OER was suppressed in the WiSEs but was substantially enhanced through the addition of an alkaline electrolyte, MOH (M = Li, Na, K), and the low-η OER was observed on the Fe−N−C surface with the elongated step edges. However, the current was still lower than that in the diluted electrolyte when the cations used were Na + and K + . By contrast, the current increased in the case of Li + , and the highest current was observed in the case of the MOH-added WiSE. This was further elucidated via the Raman spectroscopy of the electrolytes and the theoretical analysis of the OER current−potential curves.

Elucidating the Active Sites and Synergies in Water Splitting on Manganese Oxide Nanosheets on Graphite Support

“…It is a popular candidate as a support material, considering its conductivity, [24] and electrochemical properties, [25] which have already been studied in situ, [26] and especially under OER conditions. [27,28] This work presents the experimental and theoretical characterization of the OER properties of the composite material MnO 2 /HOPG consisting of MnO 2 nanosheets (MnO 2 NS) on a HOPG support. The MnO 2 NS consists of Mn-O 6 octahedral units connected by shared octahedral edges forming a highly anisotropic 2D layer with a thickness of approximately 0.7 nm and a typical lateral size in the micrometer range.…”

“…It is a popular candidate as a support material, considering its conductivity, [ 24 ] and electrochemical properties, [ 25 ] which have already been studied in situ, [ 26 ] and especially under OER conditions. [ 27,28 ]…”