Operando Revealing the Crystal Phase Transformation and Electrocatalytic Activity Correlation of MnO 2 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 MnO 2 crystallographic phases (α-, β-, and γ-MnO 2 ). The results showed that all three electrocatalysts exhibited comparable selectivity toward three-carbon products (∼90%), but γ-MnO 2 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 MnO 2 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-MnO 2 , 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 MnO 2 but also contributes to the development of a non-noble and environmentally friendly catalyst for valorizing glycerol.