The impacts of nitrogen doping on the electrochemical hydrogen storage in a carbon

Activated carbon materials doped with different nitrogen contents and nitrogen functional groups were synthesized. Nitrogen doping can improve the electrochemical hydrogen storage activity as well as the hydrophilicity of the carbon materials. Synthesized with the optimal synthesis conditions, the N-doped activate carbon demonstrated the hydrogen storage capacity of 148.4 mAh g(-1) under 100 mA g(-1) rate, and 84.3% capacity retention at a high current density of 1000 mA g(-1). 73.4% hydrogen could be preserved after a 24 hours rest at open potential. The main nitrogen functional groups on this carbon material were found to be pyrrole N, pyridine N oxide and nitro N. The density functional theory (DFT) calculations revealed that the H adsorption energy on pyridine N and pyrrole N was larger than that of pyridine N, while graphite N had no advantage in improving the H adsorption energy of carbon materials.