Theoretical studies on MgH2 dehydrogenation reaction catalyzed by metalloporphrin complexes
Magnesium hydride(MgH2)is a solid-state hydrogen storage material with potential application due to its high hydrogen storage density and environmental friendliness.But its thermodynamic stability of dehydrogenation is still an obstacle to practical application.In order to solve this problem,the effects of six transition metal porphyrin complexes(TMTPP,TM=Mn,Fe,Co,Ni,Cu,Zn)on the hydrogen storage performance of MgH2 were analyzed based on density functional theory(DFT).The results show that the enthalpy of MgH2 dehydrogenation can be reduced by 0.56～1.12 eV because of the catalysis of TMTPP,and the charge density differences,density of states and crystal orbital Hamiltonian population of the MgH2/TMTPP system were analyzed.The results show that the MgH2/CoTPP system has the lowest enthalpy of formation,mainly because of the addition of CoTPP affects the electronic properties of H,and the charge on the H atom is transferred to the CoTPP side,resulting in the lengthening of the Mg-H bond and the weakening of the bond strength,as well as the instability of MgH2.Moreover,it is found that the Mg-H bond length corresponds to the enthalpy of dehydrogenation,so the Mg-H bond length can be used as a valid descriptor to reflect the dehydrogenation performance.
density functional theoryMgH2metalloporphyrin complexesdehydrogenation
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