Sandwich-like MnO_x/MnN_0.84/Mn Electrode toward Improved Electrocatalytic Oxygen Evolution in Acidic Media

Abstract

Developing efficient and robust noble-metal-free electrocatalysts capable of catalyzing water oxidation in acidic media is highly desirable for producing H 2 while it remains a great challenge. Herein, a selfsupported MnO x /MnN 0.84 /Mn electrode with a sandwich-like configuration was prepared by consecutive steps involving a nitridation treatment and an in situ electrochemical activation process. The electrode requires overpotentials of ca. 475 and 571 mV at current densities of 10 and 100 mA cm −2 , respectively, for the oxygen evolution reaction (OER) in 1.0 M H 2 SO 4 . More impressively, the electrode remains stable for over 300 h of continuous operation at a current density of 100 mA cm −2 , which is, as far as we know, among the best values reported for Mn-based materials in the field of acidic water electrolysis. It is found that the metallic MnN 0.84 layer is not only the precursor for the formation of MnO x nanosheet electrocatalysts as the actual catalyst for the OER but also enables efficient charge transfer between the active sites at the surface and the substrate. Moreover, the anticorrosive MnN 0.84 interlayer that acts as the binder between the Mn substrate and the MnO x catalyst can protect the Mn substrate from corrosion in acidic electrolytes, highlighting the importance of interlayer modification in stabilizing electrocatalysts in harsh reaction conditions.