**1. Introduction**

Photocatalysis has wide applications in environmental, fuel production, and chemical synthesis [1, 2]. Photocatalytic materials that can convert photon energy to chemical energy are employed to split water to produce hydrogen and also produce highly reactive intermediates for chemical synthesis and reactive oxygen radicals for the degradation of organic pollutants [3]. Light absorption generates holes and electrons within the valence and conduction bands in heterogeneous photocatalysis. Those charges may migrate within the semiconductor particle and be trapped at surface sites. They'll also participate in the interfacial electron transfer processes involving the molecules of electron acceptor (A) and donor (D). within the photocatalytic organic degradation process, oxygen act as A and water as D, creating anion (O2 •–) and chemical group (OH• ) radicals. Those reactive radicals are liable for most of the oxidation of organic substances. Oxidation under these conditions is sometimes complete, giving H2O and CO2 because of the final products.

The reactions can therefore be used in water, air, or surface purification. But, the recombination of photogenerated charge carriers competes with this photocatalytic degradation process, which is a critical factor in limiting the kinetics of photocatalysts and reaction rate. To overcome this limitation, numerous photocatalysts have been developed to enhance efficiency. The nanomaterials with large surface areas, abundant surface states, and specific morphologies have emerged as pioneering photocatalysts for the dye degradation process. The optimal structure-properties relationships are essential for efficient organic pollutant degradation [4]. Significantly, the hierarchical hetero-nanostructured materials called nanoarrays give rise to separating the photogenerated electron-hole pairs to improve the photocatalytic activity further [5]. To reduce the recombination of charge carriers, the photocatalyst surface need suitable and sufficient acceptors. Since these processes involve some complicated steps, but improvement of separation and transportation of photogenerated charge carriers are the main challenges to designing highly effective photocatalysts for practical applications. Another critical issue that induces the photocatalytic activity of a catalyst is the nature of its surface/interface chemistry. The surface energy and chemisorption properties are vital in transferring electrons and energy between substances at the interface. This process allows the overpotential of redox reactions on the photocatalyst surface, which reduces photo-corrosion. Previous studies have mainly focused on the reactivity of the catalyst. Moreover, the less diffusion rate of oxygen in water, limits the photocatalytic reactions even under high light intensity. In contrast to conventional double-phase photocatalytic systems, which consist of catalysts immersed in a bulk liquid phase, triple-phase catalytic systems by supporting catalysts at the gas-liquid boundaries have been developed and exhibited outstanding performance [6].

The wettability modification of a catalyst surface includes a vital role in improving the charge transfer ability. Superwetting behavior could be a unique wetting phenomenon that always depends upon the phases. Superwettable surfaces, like super-hydrophilic and superhydrophobic surfaces, exhibit unique transport dynamics and providing exceptional prospects for reinforcing chemical process efficiency. Therefore, these materials are dramatically different from traditional materials. Superwetting catalysts have enhanced catalytic activity when introducing an air layer between the catalyst and liquid. The charge carriers from reacting interface are very fast to radicals by oxygen, and enough oxygen within the air layer can effectively capture electrons and minimize the electron-hole recombination. Superwetting materials are commonly designed by controlling surface energy, chemical compositions, and geometric structures of solid surfaces. This chapter discussed the photocatalytic organic pollutants supported superwetting materials. The discussion mainly contains widely investigated photocatalytic reactions involving gas and water molecules as reactants and products for organic pollutant degradation.
