Stable CO/H2 ratio on MoP surfaces under working condition: A DFT based thermodynamics study

Abstract

By performing a systematic DFT calculation and applying the atomistic thermodynamics analysis, the adsorption configurations, stable concentrations of nCO + mH2 co-adsorption on three representative MoP surfaces [(101), (001)-Mo and (001)-P] were investigated. Our results show that CO adsorbs much stronger than dissociative H2 on (101) and (001)-Mo surfaces but competitively with dissociative H2 on the (001)-P surface, and the hydrogen saturation coverage decreases with increasing CO pre-coverage. Ab initio atomistic thermodynamics analysis indicates the quite different CO and H2 co-adsorption manners on three surfaces under syngas atmosphere, i.e., at the equilibrium co-adsorption state, the Mo/P-terminated (101) surface and the Mo-terminated (001) surface have more versatile surface CO and H2 ratios, which are entirely different from that in the gas phase. However, the P-terminated (001) surface has only hydrogen adsorption at a wide range of conditions, which plays a role of hydrogen reservoir. Such investigations reveal that surface CO/H2 ratio could be altered by manipulating the pressures of the gas phase and temperatures, which would be beneficial to modify the syngas conversion reactivity as well as different product distributions on solid catalyst surfaces.