Adsorption and dissociation of a single water molecule on graphene-like ZnO monolayer with oxygen vacancies: a first-principles study

Abstract

Abstract ZnO monolayer (ZnO-ML) is a novel two-dimensional (2D) nanomaterial with a structure and characteristics similar to graphene. The interaction between water molecules and ZnO-ML especially oxygen vacancy (VO) decorated ZnO-ML (VO-ZnO-ML) has not been investigated yet. First-principles calculations are used to comprehensively investigate the adsorption configurations, electronic properties, and adsorption energy of a single H2O molecule on ZnO-ML. The H2O molecules and ZnO-ML interact strongly, with H2O serving as the charge accepter. ZnO-ML can maintain its nonmagnetic feature following the adsorption of H2O and the introduction of VO. For the H2O dissociation process on pure ZnO-ML, the reaction energy (E r) is 95.03 kJ ml−1 and the energy barrier (E bar) is 167.54 kJ mol−1, respectively. The presence of VO can remarkably decrease the E bar and E r to half. Moreover, the E bar and E r can be further reduced with the increase of the VO density. The hydroxyl groups can stably exist on ZnO-ML, and the adsorption becomes stronger with the increase of the VO density. These findings provide details of the interaction between H2O and ZnO-ML, thereby facilitating the further research of 2D ZnO nanomaterial in photocatalysis, electrocatalysis, and smart devices.