Insight into the effect of coexistence of CO2 and H2 on stoichiometric and defective PuO2 surfaces hydriding from first-principles study

Abstract

Studying the effect of coexistence of CO2 and H2 on plutonium hydriding is of great significance for nuclear safety storage and disposal. In this work, we studied the microscopic adsorption morphology of CO2 and H2 molecules with low and high coverage on stoichiometric PuO2 (111) and (110) surfaces. The adsorption energy results showed that both CO2 and H2 have relatively strong reactivity with the (110) surface. The CO2 molecule may be dominant in competitive adsorption with H2. The influences of the coexistence of CO2 and H2 on the adsorption and dissociation behavior for H2 on stoichiometric and defective surfaces were further researched. The CO2 adsorption configuration on the defect surface reveals that the O atom attempts to “heal” the oxygen vacancy. The results show that the presence of CO2 can weaken the interface interaction between H2 and the surface, and increase the H2 dissociation energy barrier on the surface from about 0.518 eV to about 0.791 eV. The electronic properties and work function show that the adsorbed CO2 hinders the electron interaction between H2 and surface resulting in the blocking of hydrogen adsorption and dissociation, which may be the reason for inhibiting the hydrogenation of plutonium. Our study could provide new insights into the CO2 effect on the hydriding process of active metals.