Preparation of platinum impregnated activated carbon via vacuum treatment and effect on hydrogen storage rate

Hydrogen uptake was effectively enhanced by platinum impregnated activated carbon (Pt/AC) prepared in an improved vacuum treatment process. Under high vacuum condition, the precursor of Pt could be infused into deep pores of AC. The fine Pt nanoparticles (<2 nm) were well dispersed in mesopores and micropores of AC after heating reduction. The characterization results indicate the modified vacuum treatment in this research effectively decreased the size and improved the dispersion of Pt catalysts. The impregnating condition of Pt nanocrystals obviously influenced specific surface area and pore structure, and also evidently resulted in dissimilar hydrogen adsorption behavior. Depending on the measurement of high pressure thermo-gravimetric analyzer under hydrogen atmosphere, the hydrogen adsorption rate could be accurately analyzed. Notably, the exceptional result was found in this investigation. Even with much lower surface area and pore volume, tiny Pt nanoparticles uniformly distributed in pores effectively assisted in hydrogen diffusing in deeper sites of AC via spillover phenomenon, and then substantially enhanced twice higher hydrogen uptake rate as comparing to the original process without vacuum treatment. It means the size and distribution of Pt catalysts in the pores of AC should be important key factors for hydrogen spillover behavior. (C) 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.