Hydrogen diffusion mechanism on α-AlPO4 (0001)/α-Al2O3 (0001) interface: A first-principles study

α-AlPO4 (0001)/α-Al2O3 (0001) fabricated by selective laser sintering could improve the performance at protection against H permeation compared with that of single phase α-Al2O3 and α-AlPO4. In this study, the possible interfacial structures, thermodynamics and kinetics of hydrogen diffusion in heterojunction α-AlPO4 (0001)/α-Al2O3 (0001) coating were investigated based on the density functional theory. The adsorption energy and the adsorption sites are calculated in order to obtain the most stable configuration. The hydrogen isotopic diffusion in heterojunction α-AlPO4 (0001)/α-Al2O3 (0001) is also compared with that in α-Al2O3 (0001) or α-AlPO4 (0001) surface. The interfacial binding illustrates that hydrogen is more difficult to diffuse through the grain compare with α-Al2O3 (0001) or α-AlPO4 (0001). Due to the higher saddle point energy of hydrogen migration and potential well, the hydrogen resistivity property of α-AlPO4 (0001)/α-Al2O3 (0001) is better than the single phase materials. The interface of α-AlPO4 (0001)/α-Al2O3 (0001) is predicted to be effective at suppressing hydrogen permeation.