Preparation And Hydrogen Adsorption Properties Of Cyanobacteria Based Activated Carbon

Hydrogen Energy, which is renewable and non-polluting, is considered as an attractive alternative energy. However, hydrogen storage is the key issue in the use of hydrogen. As a promissing hydrogen carrier, high surface area activated carbons have attracted a lot of interest. In this work, cyanobacteria based activated carbons activating with different activators were prepared. The influence of preparation and modification conditions on the pore structure of samples were studied. In addition, the influence of pore structure and surface chemical properties on the hydrogen storage capacity of samples were also studied with the methods of BET, SEM, and Boehm titration. The main results are as follows:(1) Characterization results of ultimate analysis and proximate analysis showed that cyanobacteria could be used to prepare activated carbon.(2) Results of the one step activation experiment showed that KOH and Zn Cl2 showed better activation performance compared with Na OH and H3PO4.(3) Results of the carbonization-activation experiments suggested that: the surface area of cyanobacteria based activated carbons which were activated with Zn Cl2 increased with the Zn Cl2/char ratio, while increased with the activation temperature after an initial decrease. Unlike with Zn Cl2, KOH showed a best activation performance when KOH/char ratio was 2, and the surface area of samples increased with the activation temperature. In addition, ACK28 showed the best performance with surface area and pore volume of 1951 m2/g and 1.092 cm3/g respectively.(4) The modification experimental study found that the surface area and pore volume of samples modified with nitric acid and phosphoric acid were decreased, which was contrary to that of samples modified with ammonium hydroxide.(5) At 77 K and 1 bar, the hydrogen capacity of cyanobacteria based activated carbons increased with the micropore volume and surface area. ACK28 showed the best hydrogen capacity, which was 1.73 wt%. All of the three chemicals showed a positive effect for the hydrogen uptake on cyanobacteria based activated carbons. In addition, the hydrogen capacity of modified samples were affected by the micropore volume, surface area and surface chemical groups, in which the surface chemical groups played a leading role. Activated carbons modified by ammonium hydroxide showed the best performance in hydrogen uptake, which was 2.52 wt% at 77 K and 1 bar, increased by 46% in comparison with ACK28.