Microwave-assistant preparation of N/S co-doped hierarchical porous carbons for hydrogen adsorption

Hydrogen storage based on physisorption into microporous materials is considered as one of the most promising technology to store and release hydrogen safely and economically. Particularly, the development of robust techniques to prepare microporous carbon materials with high hetero-atom doping amount and high specific surface area display most promising research interest. In this article, we develop a microwave-assistance method to generate hetero-elements doped porous carbon by using citric acid and urea/thiourea as sources. As a result, an O/N/S co-doped porous carbon (CT-800) displayed a high surface area (3073m(2) g(-1)) and large porosity (1.779 cm(3) g(-1)) combined with the O/N/S doping amount of 7.19 at%, 4.15 at% and 1.01 at%, respectively. Each gram of CT-800 can adsorb 267.3 cm(3) H-2 at 77 K, which is super of most of reported porous carbons, covalent-organic frameworks (COFs) and metal-organic frameworks (MOFs). We also found that the micropores are mainly contribute to high H-2 uptake ability, but the high heat of adsorption (9 kJ mol(-1)) indicates that doping atoms can also effectively improve H-2 adsorption under relative low pressure. Through atoms-in-molecules analyses, we recover that the sulfonyl group has the highest potential to adsorb H-2 molecule and further visually confirmed that the interaction between H-2 and adsorption carrier is mainly Van der Waals interaction which is of great significance for the design of carbon-based porous adsorbents.