DFT research of methane preliminary dissociation on aluminum catalyst

•The preliminary dissociation of methane is carried out via physisorption step.•The preferred adsorption site of species is edge sites of Ni4 cluster.•The adsorption priority sequence was H>O2>CH3≫CH4>H2.•The activation of O2 and desorption of H2 is promoted by Ni4 supporting on support. Using the quantum chemistry calculation module based on density functional theory (DFT), the stable adsorption states of Ni4 cluster on the surface of α-Al2O3(0001) was investigated firstly, and then the most stable adsorption configuration was selected as the representative model of supported Ni4/α-Al2O3(0001) catalyst to investigate the catalytic performance for methane preliminary dissociation. After theoretic calculation, it was found that the methane dissociation products prefer to be adsorbed on edge sites of Ni4 cluster, the adsorption priority sequence (from large to small) for the concerned species was H>O2>CH3≫CH4>H2. Comparing with pure Ni4 cluster without support, the chemical adsorption ability of Ni4 cluster to H2 molecule is decreased after supporting on support, which would promote the desorption of product H2, and thus increase the H2 yield. The adsorption energy of O2 molecule on Ni4/α-Al2O3(0001) is much higher than that of other molecules such as CH4 or H2 on Ni4 cluster surface. The OO bond length on the most stable adsorption site is elongated by 0.21Å, which would promote the activation and dissociation of O2 molecule significantly and thus might facilitate the proceeding of further reaction.