Energy conversion and loss in heterojunction photocatalysts

Photocatalysis has gained significant attention due to its wide range of potential applications. Recent studies highlight impressive energy conversion efficiency and quantum yield. This perspective aims to facilitate a better comprehension of the photocatalytic processes through analysis. Traditionally viewed as the direct conversion of light energy to chemical energy, photocatalytic processes are now understood to involve light undergoing a two-step conversion: first to electrical energy and then to chemical energy. Three major factors contribute to energy losses. Firstly, external factors include absorption, reflection, and scattering of light on the reactor surface as well as light absorption by the solution and partial light transmission across the reactor. Secondly, internal factors encompass the energy loss derived from vibrational relaxation and the disappearance of the photogenerated charge carriers. Lastly, reverse reactions induce product decomposition. In summary, achieving 100% energy conversion efficiency and quantum yield is extremely challenging and nearly impossible considering these various factors.