Hydrogen Storage in Ni/graphene and Pd/graphene Nanomaterials

Abstract

Hydrogen is a promising energy carrier that could be an alternative to the traditional carbon based fuels. Hydrogen storage in the Ni/graphene and Pd/graphene systems was investigated in the present work using Thermogravimetric Analysis (TGA). A laboratory apparatus was designed, built and applied for hydrogenation under pressure. Novel synthesis methods were developed to synthesize the graphene-based composites. Multiple characterizations have been performed to understand the sorbent structures, including the component determination and distribution, chemical state, electronic structure and metal-graphene interfaces. The hydrogen storage behavior was determined, and a hypothesis was proposed to explain the hydrogen performance in the sorbents. The Ni/graphene (5 at.% Ni, atomic percentage; 100 at.% : Ni + C) composite, charged with H2 pressure under 1 and 60 bar desorbed 0.14 wt.% H2 and 1.18 wt.%, respectively, in a TGA apparatus under a flow of argon, at room temperature. The hydrogen release could occur at an operating temperature below 150°C and was completed at 250°C. The Pd/graphene (1 at.% Pd, 100 at.% : Pd + C) composite, charged under H2 pressure of 50 and 60 bar released 6.7 and 8.67 wt.% H2, respectively, in a TGA apparatus under a flow of argon, at room temperature. The 5%Pd/graphene (5 at.% Pd, 100 at.% : Pd + C) composite charged under 60 bar H2 and dehydrogenated under the same conditions in a TGA apparatus, released 7.16 wt.% H2. The composites could discharge hydrogen below 100°C and complete the process up to 200°C. The Pd/graphene system releases relatively high hydrogen storage capacity in TGA.