Synthesis of low-cost biomass charcoal-based Ni nanocatalyst and evaluation of their kinetic enhancement of MgH2

In this study, a low-cost biomass charcoal (BC)-based nickel catalyst (Ni/BC) was introduced into the MgH 2 system by ball-milling. The study demonstrated that the Ni/BC catalyst significantly improved the hydrogen desorption and absorption kinetics of MgH 2 . The MgH 2 + 10 wt% Ni/BC-3 composite starts to release hydrogen at 187.8 °C, which is 162.2 °C lower than the initial dehydrogenation temperature of pure MgH 2 . Besides, 6.04 wt% dehydrogenation can be achieved within 3.5 min at 300 °C. After the dehydrogenation is completed, MgH 2 + 10 wt% Ni/BC-3 can start to absorb hydrogen even at 30 °C, which achieved the absorption of 5 wt% H 2 in 60 min under the condition of 3 MPa hydrogen pressure and 125 °C. The apparent activation energies of dehydrogenation and hydrogen absorption of MgH 2 + 10 wt% Ni/BC-3 composites were 82.49 kJ/mol and 23.87 kJ/mol lower than those of pure MgH 2 , respectively, which indicated that the carbon layer wrapped around MgH 2 effectively improved the cycle stability of hydrogen storage materials. Moreover, MgH 2 + 10 wt% Ni/BC-3 can still maintain 99% hydrogen storage capacity after 20 cycles. XRD, EDS , SEM and TEM revealed that the Ni/BC catalyst evenly distributed around MgH 2 formed Mg 2 Ni/Mg 2 NiH 4 in situ, which act as a “hydrogen pump” to boost the diffusion of hydrogen along with the Mg/MgH 2 interface. Meanwhile, the carbon layer with fantastic conductivity enormously accelerated the electron transfer . Consequently, there is no denying that the synergistic effect extremely facilitated the hydrogen absorption and desorption kinetic performance of MgH 2 .