Optimizing the oxygen evolution reaction: Role of crystallographic phases in support materials under acidic conditions

Abstract

Proton exchange membrane (PEM) water electrolysis is essential for the sustainable production of high-purity green hydrogen. However, the large-scale adoption of this technology is constrained by the need for advanced electrocatalysts that can achieve an optimal balance between activity and stability for the oxygen evolution reaction (OER) at the anode. This study investigates the impact of MnO2 crystal phases on the OER performance of Ru-loaded MnO2 catalysts in acidic media. We synthesized three distinct MnO2 phases-beta-, gamma-, and S-MnO2- -and subsequently deposited Ru onto their surfaces. Our findings indicate that the intrinsic OER activity highly depends on the MnO2 phase, particularly the corner-sharing (Opla) to edge-sharing (Opyr) MnO6 octahedra ratio. Notably, Ru/S-MnO2, predominantly composed of Opyr, exhibited the highest intrinsic activity, while Ru/ beta-MnO2, characterized mainly by Opla, demonstrated exceptional long-term stability, sustaining operation for over 150 h. This research underscores the significance of the octahedral coordination environment in the MnO2 phase for optimizing the Ru-Mn synergy, thereby enhancing OER catalysis.