In-Liquid Plasma-Mediated Manganese Oxide Electrocatalysts for Quasi-Industrial Water Oxidation and Selective Dehydrogenation

The production of renewable feedstocks through the coupled oxygen evolution reaction (OER) with selective organic oxidation requires a perfect balance in the choice of a catalyst and its synthesis access, morphology, and catalytic activity. Herein we report a rapid in-liquid plasma approach to produce a hierarchical amorphous birnessite-type manganese oxide layer on 3D nickel foam. The as-prepared anode exhibits an OER activity with overpotentials of 220, 250, and 270 mV for 100, 500, and 1000 mA·cm –2, respectively, and can spontaneously be paired with chemoselective dehydrogenation of benzylamine under both ambient and industrial (6 M KOH, 65 °C) alkaline conditions. The in-depth ex-situ and in-situ characterization unequivocally demonstrate the intercalation of potassium in the birnessite-type phase with prevalent Mn III states as an active structure, which displays a trade-off between porous morphology and bulk volume catalytic activity. Further, a structure–activity relationship is realized based on the cation size and structurally similar manganese oxide polymorphs. The presented method is a substantial step forward in developing a robust MnO x catalyst for combining effective industrial OER and value-added organic oxidation.