Enhancement of hydrogen desorption in magnesium hydride catalyzed by graphene nanosheets supported Ni-CeOx hybrid nanocatalyst

• A Tri-component catalyst Ni-CeOx/GNS is synthesized by impregnation-reduction method.
• Ni-CeOx/GNS catalyst exhibits enhanced catalytic effect on dehydrogenation of MgH2.
• The excellent kinetics is due to the synergistic effect of nanosize Ni, CeOx and GNS.
• JMA model shows random nucleation of Mg is the rate limiting step of dehydrogenation.

A new hybrid nanocatalyst Ni-CeOx/GNS (graphene nanosheets supported nanoscale Ni and CeOx, x = 1.69) of high surface area and porosity is synthesized by impregnation-reduction method. It is demonstrated that the Ni-CeOx/GNS nanocatalyst exhibits improved catalytic effect on the dehydrogenation performances of MgH2 compares to individual Ni/GNS, CeOx/GNS, or GNS. Differential scanning calorimetry (DSC) measurement proved that both the onset and peak desorption temperature of MgH2-5 wt% Ni-CeOx/GNS (abbreviated as MgNCG) nanocomposites can be decreased by 90.2 and 60.1 °C, respectively. Isothermal desorption kinetic test confirmed that the dehydrogenation kinetics of MgNCG nanocomposites is dozens of times higher than the pure milled MgH2, e.g. MgNCG nanocomposites can release 6.50 wt% H2 within 10 min at 300 °C with an initial hydrogen pressure of 5 KPa, superior to 0.16 wt% H2 desorbed by MgH2 under the same condition. Additionally, the activation energy (Ea) of MgNCG decreases significantly contrast with pure milled MgH2, it is proposed that the tri-component of Ni-CeOx/GNS nanocatalyst has a synergistic effect on the highly efficient dehydrogenation of MgH2.

A tri-component nanocatalyst of Ni-CeOx/GNS has a synergistic enhanced effect on the dehydrogenation of MgH2 than those of bi-component of Ni/GNS or CeOx/GNS. Figure optionsDownload as PowerPoint slide