Electrochemical decarboxylation of medium-chain fatty acids into hydrocarbons controlled by the polymer coatings on carbon-based electrodes†

Electrochemical conversion of carboxylic acids for biofuel synthesis is a significant avenue for valorizing biomass. However, the construction of catalyst coatings on electrode surfaces and their effects on the oxidative decarboxylation of medium-chain carboxylic acids remain insufficiently understood. This study examines two types of universal binders, Nafion and PTFE, along with various catalytic materials with decarboxylation activity (such as raw carbon paper (RCP), carbon black (CB), graphite flakes (GFs), carbon nanotubes (CNTs), and Pt/C) for the preparation of catalyst coatings. Through a series of characterization techniques, it was found that coatings containing Nafion exhibit hydrophilic and dense properties, while PTFE-containing coatings display hydrophobic characteristics and a macroporous morphology. Due to these attributes, Nafion coatings are prone to blockage during the electrolysis of medium-chain carboxylic acids (octanoate ions), which inhibits the decarboxylation reaction and favors the occurrence of the oxygen evolution reaction (OER). In contrast, the macroporous structure of PTFE coatings not only facilitates exposure of the catalytic active sites but also hinders the diffusion of water molecules, thereby reducing the OER. This study provides valuable insights and design considerations for the development of highly active electrochemical decarboxylation electrodes.