Electrochemical hydrogen storage of Pt and Ni nanoparticles-electrodeposited multi-walled carbon nanotube/micro-hybrid composite

Abstract

Cyclic voltammetric (CV) hydrogen storage of multi-walled carbon nanotube (MWCNT)/micro-hybrid composites is studied. For this purpose, a three-electrode system is utilized using a Pt disk as counter, Ag/AgCl (3.0M) as reference and MWCNT/micro-hybrid composite as working electrodes. Optimum percentage of MWCNTs in the composite matrix is suggested to 50% (w/w). Solution of NaOH (6.0M) is also selected as electrolyte. Hydrogen adsorption/desorption behavior of composite is investigated based on CV measurements in the range of −1.60 to +0.50V (vs. Ag/AgCl). Chrono-amperometery is applied to estimate active surface area of the composite (0.145m2g−1) and diffusion coefficient (3.41×10−11m2s−1) of adsorbed hydrogen. According to the results, the active surface area and also the diffusion coefficient of H2 are significantly promoted when thermally activation of the CNT-based composite by O2, or assisting to ultraviolet (UV) radiation and/or microwave irradiator. In this fstudy, the effect of nanoparticles such as Ni and Pt is also investigated via electrodeposition of Ni(II) and PtCl42- on the CNT-based composite using single- and double-pulse methods. According to the voltammograms, significant enhancements are observed in the reduction peak currents of hydrogen, when decorating Ni or Pt nanoparticles. Ultimately, hydrogen capacity of fabricated composite is evaluated to 4.62wt.%, after charging the CNT-based composite for a certain time (∼1h).