Synthesis and characterization of Pt-N-doped activated biocarbon composites for hydrogen storage

Abstract

Activated carbon (AC) from bamboo having super surfaces areas of 3155 m2/g were firstly doped with nitrogen by microwave assisted hydrothermal methodology, to obtain nitrogen doped activated carbon (NAC) with N content of 1.64 wt%. Pt-AC composites with Pt nanoparticles at various loadings of 2.87–6.73 wt% were then prepared by wet impregnation methods. N2 adsorption at 77 K, ICP-OES, XRD, TEM, EDX, SEM, and H2 chemisorption were used to investigate the morphological, structural and textural properties of AC composites. The results showed that i) increasing Pt content gave rise to an increase of the metal particle size, ii) N doping resulted in smaller Pt nanoparticle and hence better dispersion, and iii) the surface area decreased after Pt doping due to the pore blocking. Hydrogen storage capacities were measured both at 77 K up to 1bar and 298 K up to 4 MPa. The capacity of hydrogen storage at 77 K was closely related to the porous texture, whether the heteroatom or metal Pt doped, and the hydrogen storage on Pt doped NAC at 298 K presented much higher enhancement factor of 1.82 compared with the Pt doped AC due to the spillover effect, depending on Pt content. The hydrogen uptakes/storage on Pt-N-doped AC were also higher than on pure AC doped with Pt due to the further enhancement with the spillover effect, which should be attributed to the better Pt dispersion and smaller Pt nanoparticle size obtained.