An Operando-Raman study on oxygen evolution of manganese oxides: Roles of phase composition and amorphization

摘要: Abstract Manganese oxide catalysts exist in various forms of polymorphs, which have direct influence on their oxygen evolution reaction (OER) performance. However, structure flexibility under working conditions remains a great challenge for identifying active structures. In this work, OER performances manganese electrocatalysts with representative phase compositions (birnessite, bixbyite) were examined using operando-Raman spectroscopy. The results indicate that containing birnessite composition do not exhibit apparent activity before an charging activation process. Shifting Raman peaks around ∼640 cm−1 can serve as indicator predicting onset potentials. amorphization mixed-phase catalyst is favor and reduces the potential by 120 mV. Moreover, coexistence bixbyite-like Mn(III) center amorphized combines abilities catalyzing both electrochemical chemical steps, creating more bias-efficient channel. This leads to lowest Tafel slope improved high overpotential region, suggesting amorphous structural facilitate kinetics.