Critical Review of Photocatalytic Reactor Designs for Environmental Applications

Photocatalytic processes are a viable alternative to reduce fossil fuel use and global warming. The photocatalytic approach has the potential to restore the globe to its equilibrium state through a combination of energy production (solar cells), energy conversion (CO2 to fuels, water splitting), and environmental remediation (degradation). Despite the rocketing research on photocatalytic materials for photocatalytic degradations, research on photocatalytic reactors is urgently required to match the explosive growth of research on photocatalytic materials. Although numerous innovative, futuristic designs are brought up by various research fields, the development of photocatalytic reactors to achieve commercialization objectives has not yet attained maturity. The photocatalytic treatment of contaminants is typically influenced by three factors: the pollutant (liquid), the catalyst (solid), and light (massless). It is difficult to advance the research further since all three components are in different phases. In order to decrease the restrictions brought on by photocatalysis, such as mass transfer and light penetration, numerous approaches have been proposed. As of now, many reactors have been constructed in a variety of sizes and shapes, from bench-top and laboratory designs to industrial pilot scales with different operational modes. The overall efficiency of the photocatalytic reactor is influenced by its working components. Reactor types classified according to their catalyst installation and geometry have been identified as the primary groups and their advantages and disadvantages were assessed. Additionally, several potential modifications and designs for sunlight-driven photocatalytic reactors are discussed. Finally, conclusions and future improvement points were highlighted as well as a collective tabulated comparison of the reactor's advantages and disadvantages.