A review on adsorption-enhanced photoreduction of carbon dioxide by nanocomposite materials

The large amount of CO2 emissions from the increasing consumption of fossil fuels is a potential cause for global warming. Photocatalytic reduction of CO2 using sunlight is considered as an attractive method for mitigating CO2 emissions. Extensive amount of researches on CO2 photoreduction are available, which tend to focus on the types of photocatalysts, the photocatalytic activity, and photoconversion efficiency. However, CO2 adsorption in the CO2 photoreduction process has been overlooked, despite it being an initial and important step. Recently, there has been an increase in the number of publications investigating the effects of CO2 adsorption on the CO2 photoreduction process. Thus, this review summarizes the research progress in this regard. This review focuses on the different CO2 adsorption modes and characterization methods as well as the factors influencing CO2 adsorption such as surface area, surface basicity, surface functional groups, surface defects, and exposed crystal facets. Furthermore, the design of nanocomposites that consist of photocatalysts and CO2 adsorption promoters are reviewed and discussed. It has been demonstrated that the CO2 photoreduction performance can be increased by utilizing CO2 adsorption in various types of nanocomposites, including metal oxides, chalcogenides, layered double hydroxides, and metal organic frameworks. This review provides a unique perspective in the design of nanocomposite photocatalysts with the goal of efficient CO2 photoreduction.