Progress on gas-solid phase photoreactor and its application in CO2 reduction

The burgeoning field of photocatalytic reduction of CO2 has emerged as a remarkable promising solution to address some of the most pressing global energy and environmental issues which we face today. Researchers around the global have been striving to augment the efficiency of CO2 photocatalytic reduction, employing strategies that range from modifying the fundamental properties of photocatalysts to suppress the electron-hole recombination, optimizing reaction conditions to achieve the highest yield, and conceptualizing and constructing photoreactors to improve the adsorption process. Among these factors, the photoreactor plays a critical role in enhancing the overall photocatalytic efficiency. Understanding the various types of photoreactors and their operational dynamic can significantly influence the experimental design, thus guiding the data collecting and analysis. Compared to the solid-liquid phase, gas-solid phase photocatalytic reduction of CO2 is gaining recognition for its potential advantages, such as rapid molecular diffusion rates, adjustable CO2 concentrations, and uniform and sufficient light exposure. Nonetheless, the currently reported gas-solid phase photoreactors are still in their infancy. In this review, we dissect the underlying mechanism of photocatalytic CO2 reduction and the performance evaluation criteria of photoreactors, and review the development process of gas-solid phase photoreactors. Furthermore, we explore the evolution of gas-solid phase photoreactors, elucidating their growth trajectory and future possibilities. We present a comprehensive classification of gas-solid phase photoreactors, offering a new insight into their design and functionality, summarizing their strengths and inevitable limitations. Finally, we provide a forward-looking perspective on the future developmental prospects of carbon neutrality.