Functionalized and Schiff base based multi walled carbon nanotubes for hydrogen storage

Abstract

The depletion of fossil fuels in the near future and their environmental problems will lead to an energy crisis. Due to its renewability, high energy density, and low emissions, hydrogen is an alternative energy source to fossil fuels. However, it faces great difficulties in terms of storage. Therefore, the aim of this study is to improve the storage capacity of MWCNT with low hydrogen storage capacity by modification and metal doping. For this purpose, firstly, the hydroxylated and Schiff base based MWCNT structures were synthesized from MWCNT. Then, the synthesized MWCNT-O-APTES-TFA was doped with different metals by solvent removal method. The characterization of samples were performed by BET, FTIR-ATR, DTA/TG, TEM and SEM/EDX devices. It was found that modification and metal doping were important variables in changing the surface areas of the samples. FTIR-ATR showed vibration bands belonging to hydroxyl groups and Schiff bases attached to the structure of MWCNT. The modified MWCNTs are looser, the tube lengths are shorter and the tendency to cluster is less. EDX and mapping analyses showed the presence of metals in the doped samples and that the metals were distributed homogeneously in the samples. The modification changed the degradation step temperature and step number of MWCNT. TEM image confirmed the tubular structure and nano-nature of MWCNT. The hydrogen storage capacity of the synthesized and doped samples was measured as a function of pressure at cryogenic temperature using Hiden IMI PSI gas storage device. The hydrogen storage capacity of MWCNT increased with modification and increasing pressure. The hydrogen storage capacities of the doped samples were different from each other. MWCNT-O-APTES-TFA-Co had the highest hydrogen storage capacity among the doped samples, while it was MWCNT-OH among the modified samples. The results showed that modification and doping were important parameters in improving the hydrogen storage capacity of MWCNT.