Electronic structure modulation of MnO2 by Ru and F incorporation for efficient proton exchange membrane water electrolysis

Abstract

Hydrogen is a sustainable energy carrier that can be produced via water electrolysis (WE). However, the use of precious metals as anode catalysts increases the cell stack price and hinders the practical implementation. Therefore, MnO₂ has been introduced as a catalytic support material to maximize the utilization of precious metals at a given loading. However, their oxygen evolution reaction (OER) activities remain unsatisfactory owing to lack of precise structural control. Here, Ru and F incorporation successfully modulates the electronic structure of MnO₂ for application to proton exchange membrane water electrolysis (PEMWE). Optimization of the synthesis conditions produced a (Mn_0.94Ru_0.06)O₂:2.5F catalyst, which showed a high mass activity. X-ray spectroscopic and electrochemical characterizations revealed that the OER activity increased with the Mn³⁺/Mn⁴⁺ ratio and oxygen vacancies. In addition, practical applicability was demonstrated by applying (Mn_0.94Ru_0.06)O₂:2.5F as the anode catalyst in a PEMWE cell.