Polymer-mediated exsolution and segregation of ruthenium oxides on β-MnO2 for durable water oxidation in proton-exchange membrane electrolyzers

Abstract

The development of acid-stable and low-noble-metal electrocatalysts for the oxygen evolution reaction (OER) is challenging but demanding for the large-scale application of proton-exchange membrane water electrolyzers (PEMWE). Herein, taking advantage of the densely packed and stable crystalline structure of β-MnO₂ and the dopant-induced lattice strain, a high-performance OER catalyst with low Ru loading is developed via the thermally-driven and polymer-mediated exsolution and segregation process. While high-resolution microscopic studies clearly illustrate the Schottky mechanism involved in the formation of polycrystalline RuO_x-containing grains anchored to the MnO₂ support, spectroscopic findings unveil a significantly altered electronic structure with reduced Mn and Ru chemical states, as well as populated vacancies. Consequently, the best catalyst Ru–MnO₂-PT achieves remarkable OER activity in acidic medium, requiring an overpotential of only 163 mV to reach a current density of 10 mA cm⁻², in addition to excellent electrolytic stability, enabling a prolonged operation of PEMWE for over 2000 hours. This study sheds new light on controllably regulating the exsolution and segregation process of noble metal-doped transition metal oxides for the fabrication of highly robust OER catalysts.