Organogel Polymer Electrocatalysts for Two-Electron Oxygen Reduction

Abstract

Polymer gels, renowned for unparalleled chemical stability and self-sustaining properties, have garnered significant attention in electrocatalysis. Notably, organic polymer gels that exhibit temperature sensitivity and incorporate suitable polar nonvolatile liquids, enhance electronic conductivity, and impart distinct morphological features, but remain largely unexplored as electrocatalysts for oxygen reduction reaction (ORR). To address this issue, an innovative strategy is proposed for synergistic modulation of the rigidity of mainchain molecular skeleton and length of alkyl sidechains, enabling the development of organogel polymers with a sol–gel temperature-sensitive phase transition that promises high selectivity and enhanced activity in electrocatalytic processes. Notably, the shortening of alkyl sidechain length can significantly affect the gelation behavior and internal microstructure of the catalyst, which modifies the electron state, ultimately impacting the catalytic activity of the gel polymer catalysts. In particular, phenyl-containing Ph-FL1 with short alkyl sidechains demonstrates outstanding 2e⁻ ORR activity in alkaline medium, achieving a remarkable hydrogen peroxide (H₂O₂) selectivity of 98.6% with an impressive yield of 4.08 mol g⁻¹ h⁻¹. This performance surpasses most metal-free carbon-based electrocatalysts. Through theoretical calculation, the carbon atom (site-3) of C═N group is identified as potential active sites, representing a significant advancement toward designing cost-effective and efficient ORR electrocatalysts.