Direct synthesis of N, S co-doped porous carbons using novel organic potassium salts as activators for efficient CO2 adsorption

In the current work, we proposed the use of two organic potassium salts, 4-morpholineethanesulfonic acid (MES) potassium salt and 1,4-piperazinediethanesulfonic acid (PIPES) dipotassium salt, as novel and tri-functional activators for the synthesis of N, S co-doped carbons (NSCDCs). The organic potassium salts served as acti-vator and N/S source at the same time, allowing direct synthesis of NSCDCs with N/S free precursor. In order to verify this hypothesis, N,S free hydrochar derived from glucose was selected as the carbon source. NSCDCs with high and tunable surface area (1673-2235 m2/g), N content (3.44-5.80 wt%), and S content (5.26-8.72 wt%) were obtained. Physicochemical properties of the carbons were mainly decided by potassium salt and activation temperature. The NSCDCs were also investigated for their CO2 adsorption properties. At 25 degrees C and 1 bar, high CO2 uptake of 3.04-3.99 mmol/g was achieved by the carbons. Qst of the NSCDCs was 22.6-28.7 kJ/mol, and CO2 adsorption selectivity over N2 was 10.5-17.3 at 25 degrees C and 1 bar. At 25 degrees C and 20 bar, CO2 uptake increased to 11.26-17.29 mmol/g, and exhibited linear dependence on specific surface area. The current work indicated that MES potassium salt/PIPES dipotassium salt could be used as activator for convenient synthesis of NSCDCs as efficient CO2 adsorbents.

Automated summary

In this study, two organic potassium salts were proposed as novel and tri-functional activators for the synthesis of N, S co-doped carbons. The organic potassium salts served as activator and N/S source, allowing direct synthesis of NSCDCs with high surface area, N content, and S content.