Design and Application of a High-Surface-Area Mesoporous δ-MnO2 Electrocatalyst for Biomass Oxidative Valorization

The design and application of electrocatalysts based on Earth-abundant transition-metal oxides for biomass valorization remain relatively underexplored. Here, we report a nanocasting route to synthesize mesoporous delta-MnO2 with a high surface area (198 m(2)/g), high pore volume, and narrow pore size distributions to address this issue. By taking structural advantages of mesoporous oxides, this mesoporous delta-MnO2 is employed as a highly efficient, selective, and robust anode for 5-hydroxymethylfurfural (HMF) electrochemical oxidation to 2,5-furandicarboxylic acid (FDCA) with a high yield (98%) and faradic efficiency (98%) under alkaline conditions. The electrocatalyst is also effective for the more difficult HMF electro-oxidation under acidic conditions, forming both FDCA and maleic acid as value-added products in a potential-dependent manner. Experimental results combined with theoretical calculations provide insights into the reaction kinetics and the reaction pathways of electrochemical HMF oxidation over this advanced electrocatalyst. This work thus showcases the rational design of non-noble metal electrodes for multiple applications, such as oxygen evolution, water electrolysis, and biomass upgrading with high energy efficiency.

Automated summary

This study synthesized a mesoporous delta-MnO2 electrocatalyst with high surface area, high pore volume, and narrow pore size distributions using a nanocasting route. The electrocatalyst exhibited high efficiency, selectivity, and robustness for the electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) under alkaline conditions. The reaction kinetics and pathways of the electrochemical HMF oxidation over this advanced electrocatalyst were investigated and provided insights.