materials, photocatalysis has been demonstrated as a promising
technology for mitigation of urban air pollution (i.e. asphalt,
pavement, and wall) [11e17].
TiO2, with favorable features of durability and stability, ensures
its wide applications in the chemical, medical, biological, environmental,
and solar energy fields [18]. In the HVAC field, the
overwhelming majority of the catalysts are TiO2 and its derivatives.
In this review, the principles of the photocatalysis and two major
applications of PCO technologies in the field of the HVAC systems
and construction and building materials are summarized in detail.
In addition, the technical challenges that hinder the UV-PCO
technologies from being widely commercialized are discussed. In
the end, future research priorities are proposed in order to break
through current bottlenecks. Fig. 2 is a flowchart depicting the
framework in this review.