Nitrogen-doped carbons prepared from eutectic mixtures as metal-free oxygen reduction catalystsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ta08630b

• Main Authors: López-Salas, Nieves, Gutiérrez, María C, Ania, Conchi O, Muñoz-Márquez, Miguel A, Luisa Ferrer, M, Monte, Francisco del
• Format: Article
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c5ta08630b

Deep eutectic solvents (DESs) composed of resorcinol, either 2-cyanophenol or 4-cyanophenol, and choline chloride were used for the synthesis of hierarchical nitrogen-doped carbon molecular sieves. Carbons were obtained with high conversions by polycondensation of resorcinol and either 2-cyanophenol or 4-cyanophenol with formaldehyde, and subsequent carbonization at 800 °C in nitrogen atmosphere. The nitrogen content was ca. 2.4 wt%, revealing an excellent nitrogen-doping efficiency for cyanophenol derivatives when used in the form of DES. The use of either 2-cyanophenol or 4-cyanophenol modified the contribution of quaternary-N valley groups in the resulting carbons, being larger in carbons coming from 4-cyanophenol than in those coming from 2-cyanophenol. The hierarchical porous structure was composed of micro-, meso- and macropores, and the diameter distribution of mesopores was also related to the use of either 2-cyanophenol or 4-cyanophenol. These structural and compositional differences were critical for the use of the resulting hierarchical nitrogen-doped carbons as efficient metal-free electrocatalysts. In particular, the carbons coming 4-cyanophenol proved particularly effective in the direct reduction of oxygen to OH − (H 2 O in acidic solution) through a four-electron (4e − ) process with high catalytic activity and selectivity, and longer stability and stronger tolerance to crossover effects than platinum-based electrocatalysts. Deep eutectic solvents (DESs) composed of resorcinol, either 2-cyanophenol or 4-cyanophenol, and choline chloride were used for the synthesis of hierarchical nitrogen-doped carbon molecular sieves.