Operando Revealing the Crystal Phase Transformation and Electrocatalytic Activity Correlation of MnO₂ toward Glycerol Electrooxidation

In this work, we report for the first time a comprehensive operando investigation of the intricate correlation between dynamic phase evolution and glycerol electrooxidation reaction (GEOR) performance across three primary MnO₂ crystallographic phases (α-, β-, and γ-MnO₂). The results showed that all three electrocatalysts exhibited comparable selectivity toward three-carbon products (∼90%), but γ-MnO₂ exhibited superior performance, with a low onset potential of ∼1.45 V_RHE, the highest current density of ∼1.9 mA cm^-2 at 1.85 V_RHE, and reasonable stability. Operando Raman spectroscopy revealed the potential-induced surface reconstruction of different MnO₂ structures from which a correlation among the applied potential, electrocatalytic activity, and product distribution was identified. The higher the applied potential, the greater conversion from the original structure to δ-MnO₂, resulting in lower C-C cleavage and higher 3C product selectivity. This study not only provides a systematic understanding of structure-controlled electrocatalytic activity for high selectivity toward 3C products of MnO₂ but also contributes to the development of a non-noble and environmentally friendly catalyst for valorizing glycerol.