Influence of molecular structure of extractor molecules on liquid-liquid extraction of oxide particles and properties of composites

Interest in particle extraction through liquid-liquid interface (PELLI) technology is motivated by the need to transfer particles directly from the synthesis medium to the device processing medium. This method avoids the difficulty encountered by conventional re-dispersion methods where particles agglomerate during the drying stage. We develop PELLI strategies to transfer MnO2, ZnO and CeO2 particles that are synthesized in aqueous media into 1-butanol using extractors containing phosphonate and carboxylic groups. We demonstrate that, in addition to head-tail (HT) surfactants, molecules containing two hydrophilic end groups (HTH) can also be employed as extractors, a finding that opens new PELLI applications. We demonstrate this new approach using multifunctional HTH molecules as both PELLI extractors, and charged dispersing agents for the electrophoretic deposition (EPD) of particles that are transferred to an EPD processing medium. Using the HTH extractors for PELLI, we fabricate MnO2-based bulk electrodes for electrochemical supercapacitors (ES) that exhibit superior electrochemical performance. These high active mass loading ES electrodes have a capacitance of 5.7 F cm−2 (157 F g−1) and 2.5 F cm−2 (67 F g−1) at 2 and 100 mV s−1 scan rates, respectively, with low impedance. In another strategy, the use of HTH extractor for particle transfer to screen printing processing medium facilitates the fabrication of efficient thin film SC electrodes. Measurements provide insight into the influence of anchoring groups and extractor molecule structure on the extraction efficiency and electrochemical performance.