MgH2–TiF4-MWCNTs based hydrogen storage tank with central tube heat exchanger

Abstract

Improvement of hydrogen sorption kinetics of MgH2–TiF4-MWCNTs based tank by addition of central tube heat exchanger and enhancement of hydrogen diffusion is proposed. After doping with TiF4 and MWCNTs, dehydrogenation temperature of MgH2 decreases significantly (ΔT = up to 90 °C). Superior hydrogen permeability, favoring hydrogen sorption kinetics is detected at hydrogen supply side to the middle of the tank, while effective heat transfer during exothermic hydrogenation is assured by the temperature increment of heat exchanger fluid (compressed air at room temperature). Hydrogen desorption and absorption can be completed within 120–150 and 25 min, respectively, up to twice as fast as the tank without heat exchanger from the previous studies. Due to fast hydrogenation rate resulting in short reaction time at high equilibrium temperature (up to 390 °C), particle agglomeration and/or sintering of MgH2 upon cycling are prevented. Enhanced de/rehydrogenation rates and suppression of MgH2 particle growth during cycling yield to considerable reversibility upon 20 de/rehydrogenation cycles with storage capacity up to 5.60 wt % H2 (82% theoretical value). By increasing operating temperature to 330–335 °C, hydrogen released with constant flow rate of 0.30 standard L/min is prolonged up to three times, favoring electrical power production of PEMFC stack. Electrical performances obtained from PEMFC stack (13 single cells) supplied with hydrogen gas from MgH2-based tank are also investigated.