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

Abstract

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.

Mining the Carbon Intermediates in Plastic Waste Upcycling for Constructing C–S Bond

“… Three dominant peaks, v 1 to v 3 , can be identified in the range of 200–700 cm –1 (Figure d). To elaborate, the frequency range of v 1 (620 cm –1 to 650 cm –1 ) is linked to Mn–O stretching vibrations that are perpendicular to the sheet of MnO 6 octahedra and symmetric stretching of the Mn–O bond within the MnO 6 octahedra unit, while v 2 (570 and 590 cm –1 ) signifies the Mn–O stretching vibration occurring within the plane of MnO 6 octahedra. − Compared to the previously reported Raman spectra of fine-crystalline MnO 2 , such as α-MnO 2 , γ-MnO 2 , and δ-MnO 2 , a significant blue shift of the v 2 band is observed in both Amo-MnO 2 and L-Cry-MnO 2 . This shift is attributed to the structural distortions in both samples, verifying their amorphous characteristics.…”

Advancements in catalysts for glycerol oxidation via photo-/electrocatalysis: a comprehensive review of recent developments

“…γ-MnO 2 delivered a superior performance with a lower onset potential owing to the preferential adsorption of secondary –OH groups on the surface. 191 MnO 2 fabricated on carbon paper in acidic media showed an impressive stability of 865 h along with a lower onset potential of 1.36 V RHE (270 mV lower than that for the OER) and lower Tafel slope (243.1 mV dec −1 ). The in situ Raman and DFT studies revealed that glycerol addition enhanced the stability of MnO 2 , inhibiting its dissolution and lattice oxygen processes, which led to high stability of electrode and selective production of FA.…”