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

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 (V-O) decorated ZnO-ML (V-O-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 V-O. 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 V-O 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 V-O density. The hydroxyl groups can stably exist on ZnO-ML, and the adsorption becomes stronger with the increase of the V-O 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.