NOVELTY - Hydrogen is contacted with an extended pi-conjugated substrate (E) in the presence of a hydrogenation catalyst under hydrogenation conditions to form a partially hydrogenated extended pi-conjugated substrate (P), and store hydrogen. The formed substrate is subjected to catalytic dehydrogenation in the presence of a preset amount of a dehydrogenation catalyst to release hydrogen from the hydrogenated substrate.    USE - Used for storing and releasing hydrogen using a dispenser in a fueling process (both claimed) used for fuel cells used for mobile vehicular systems. Also hydrogen is used in the chemical and petroleum processing industry.    ADVANTAGE - The storage and release of hydrogen is simply and safely enabled at practical operating temperature and pressure, with favorable gravimetric and volumetric storage density. The extended pi-conjugated substrate and their hydrogenated derivative are less volatile, and hence separation unit for separating substrate from hydrogen is not required.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a dispenser, which dispenses a liquid (1) and retrieves a liquid (2), where the dispenser comprises conduits (1, 2) having orifices (1, 2) for dispensing liquid (1), and retrieving liquid (2) in countercurrent direction w.r.t liquid (1), respectively;    (2) the dispensing and retrieving of liquids (1, 2), where the dispenser is contacted with compartments (1, 2), the liquid (1) is transferred to compartment (1) through conduit (1), and liquid (2) contained in compartment (2) is transferred to conduit (2) and liquid (1) is dispensed and liquid (2) is retrieved; and    (3) a fueling process in which the dispenser is placed in flow communication with compartments (1,2), where liquid (1) comprises partially hydrogenated pi-conjugated substrate and liquid (2) comprises pi-conjugated substrate, and a portion of liquid (1) residing in compartment (1) is transferred into a hydrogen generator and contacted with dehydrogenation catalyst under dehydrogenation condition to produce hydrogen and liquid (2) and a portion of liquid (2) is transferred into compartment (2), liquid (1) is transferred to compartment (1) through conduit (1), and liquid (2) is transferred through conduit (2), enabling fueling process.    DESCRIPTION OF DRAWING(S) - The graph shows enthalpy change of hydrogenation of isolated double bonds.