Comparative study on electrochemical hydrogen storage of nanocomposites based on S or N doped graphene quantum dots and nanostructured titanium niobate

Abstract

It is necessary to boost extremely effective and sustained mixed metal oxide-supported materials that can participate in the energy storage process. Herein, TiNb2O7 nanostructure-embedded S- or N-doped graphene quantum dots (S-GQDs/TN or N-GQDs/TN) with interconnection structures are synthesized through a facile alcothermal procedure using in situ chelating and stabilizing agents composed of acetylacetone (Acac) and amines that have different lengths of carbon chains. The interconnected S/N-doped GQDs make the nanocomposites more electron-rich and have improved conductivity, and pyridinic nitrogen produces electrophilic active sites to facilitate hydrogen absorption on the material. The as-prepared nanocomposites exhibited preferable activity for hydrogen sorption. The outstanding electrochemical performance of GQDs/ TN nanocomposites is principally ascribed to the contributory impacts of TiNb2O7 nanoparticles and GQDs, which can not only equip valuable effective sites, uncomplicated availability of electrolyte and spreading of hydrogen but also engage its excellent conductivity and efficient structure. Additionally, the morphology and electrolyte concentration were optimized as important parameters. The hydrogen storage capacities of pristine TN microspheres and nanoparticles are 200 and 979 mA h g−1 and increase with modification by GQDs (discharge capacities for S-GQDs/TN3 and N-GQDs/TN3 measured 1234 and 2433 m Ah g−1). In addition, by increasing the electrolyte concentration, the hydrogen storage capacity was increased.