Hydrogen storage in nickel catalysts supported on activated carbon

We have studied hydrogen storage in a commercial activated carbon impregnated with nickel. High-pressure (20–30 bars) hydrogen uptake at room temperature was assessed using a high-pressure volumetric adsorption–desorption system. The properties of the prepared materials were studied by means of N2N2 physisorption, X-ray diffraction, transmission electron microscopy, metal surface area, hydrogen temperature programmed reduction and hydrogen temperature programmed desorption. Various factors influencing the level of hydrogen uptake (metal precursor, metal content, method of preparation) were examined and discussed. It is concluded that the hydrogen stored is loosely chemisorbed on the carbonaceous material surface as spilt-over species through H2H2 dissociation on the metal phase then migration onto the support. This hydrogen would also be directly adsorbed on carbon acceptor sites induced by H2H2-pretreatment at 623 K. In both cases, the stored hydrogen directly desorbs from the active carbon support.