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

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 (Er) is 95.03 kJ ml−1 and the energy barrier (Ebar) is 167.54 kJ mol−1, respectively. The presence of VO can remarkably decrease the Ebar and Er to half. Moreover, the Ebar and Er 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.