Effect of nitrogen and sulfur co-doping on the performance of electrochemical hydrogen storage of graphene

In recent decades, finding a solution to replace metal catalysts with inexpensive and available elements has been investigated extensively. Carbon nanomaterials doped with heteroatom such as (N, B and S) which do not have any metal content can provide sustainable materials with a remarkable electrocatalytic activity that can compete with their metal counterparts. Doped graphene has been considered as an electrode material for oxygen reduction reaction, supercapacitor and Li-ion batteries. In this present account, co-doped graphene with nitrogen and sulfur was studied in order to investigate their electrochemical hydrogen storage performance. The dual doped sample was prepared via a simple hydrothermal method, using thiourea as a nitrogen and sulfur source. The nitrogen and sulfur co-doped graphene (NSG) showed excellent electrical conductivity and electrochemical performance compared with the nitrogen doped graphene (NG) and graphene oxide (GO). Doping graphene with foreign atoms is a method to create a semiconducting gap in it and can act as an n-type semiconductor, therefore the electrochemical performance is remarkable when used as an electrode. According to the results by increasing the electrical conductivity of graphene, the storage capacity of hydrogen was increased. The discharge capacity of GO after 20 cycles was increased from 653 mAh/g to 1663 mAh/g (5.88 wt% hydrogen) and 2418 mAh/g (8.55 wt% hydrogen) in single doped graphene (NG) and co-doped graphene (NSG), respectively. The prepared samples were characterized via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmet-Teller analysis (BET), vibration sample magnetometer (VSM) and infrared spectrum (FT-IR).