Deterioration mechanism of vanadium dioxide smart coatings during natural aging: Uncovering the role of water.

• The role of water in the deterioration process of VO 2 is discussed. • Humidity is a key factor in the rate of VO 2 natural aging. • Water affects the adsorption of oxygen on VO 2 surfaces by hydrogen bonding. • Water is involved in the reaction in the form of combined water. • Water accelerates aging by destroying the dense structure of VO 2. Vanadium dioxide (VO 2) has already been widely concerned as a thermochromic smart window material. However, the Achilles heel of VO 2 is susceptible to degradation by water and oxygen in the air, which has limited its commercialization. Until now, it has remained unclear what effect water has on the deterioration of VO 2 , hindering the solution to this dilemma. In this work, the degradation mechanism of VO 2 during natural aging was proposed based on density functional theory (DFT) calculation and experimental analysis, and the role of water in the degradation process was discussed in detail. The results showed that water affects the deterioration reaction by influencing the adsorption behavior of oxygen on the VO 2 surface, destroying the dense structure, and participating in the reaction in the form of combined water. This work fills the degradation mechanism gap of VO 2 , helps to design high-performance structures of VO 2 -based smart coatings, and provides theoretical guidance to solve the problem of VO 2 weatherability. [ABSTRACT FROM AUTHOR]