Solar energy offers sustainable and versatile solutions through photothermal, photovoltaic, and photocatalytic methods, using various catalysts for efficient energy conversion.
Among various sustainable energy sources, solar energy is considered promising due to its inexhaustible, universal, large capacity, and environmentally friendly advantages.
Solar energy can be used by photothermal, photovoltaic and photocatalytic methods, including:
Solar energy can be applied in many fields.
Catalysts play an important role in all processes of solar energy conversion.
The three important reactions of solar to chemical energy conversion include: light-driven water splitting, light-driven CO2 reduction, organic photosynthesis, and other photocatalytic reactions.
Solar-driven water splitting is a promising method for sustainable hydrogen production.
The ideal photocatalyst should have the characteristics of low price, abundant reserves and low toxicity. Traditionally used photocatalyst materials are mainly limited to inorganic semiconductor materials such as oxides (such as TiO2, Cu2O) and sulfides.
In addition, some semiconductors and their nanostructured composite materials have become star materials and show high efficiency in these reactions. These include transition metal oxygen-containing salts (phosphate, tungstate, vanadate, titanate), composite oxidation Materials (multi-metal oxides, oxynitrides, oxysulfides, oxyhalides), non-metallic materials (carbon, nitride, black phosphorus), etc.
Among them, the nanocomposite photocatalyst based on gC3N4 is used as a low-cost, strong, visible light active photocatalyst for water splitting, CO2 conversion and organic synthesis.
Photothermal catalysis (PTC) can use full-spectrum sunlight to stimulate the synergy between photocatalysis (PC) and thermal catalysis (TC).
This synergy not only realizes the high utilization efficiency of solar energy, but also minimizes the energy consumption compared with a separate PC and TC.
Photothermochemical materials play a key role in achieving high photothermal catalytic activity. The ideal material must meet several functional requirements:
Purify various pollutants through photocatalytic oxidation (PCO), such as volatile organic compounds (VOC) or inorganic gases (NOx, SOx, CO, H2S, ozone, etc.) at relatively low concentrations.
Photocatalysis has used a variety of materials as catalysts. For example, metal oxides include binary compounds (TiO2, ZnO, WO3, Fe2O3, ZrO2, etc.), ternary compounds (vanadate, tantalate, tungstate and bismuthate, etc.) and other complex oxyhalides. 
Figure 3. Photocatalysts for air purification
Feifan Wang. (2017). “Recent Progress in Semiconductor-Based Nanocomposite Photocatalysts for Solar-to-Chemical Energy Conversion.” Advanced Energy Materials 7(23): 1700529.
Rong Ma. (2020). “Review of synergistic photo-thermo-catalysis: Mechanisms, materials and applications.” International Journal of Hydrogen Energy 45(55): 30288-30324.
Yash Boyjoo. (2017). “A review on photocatalysis for air treatment: From catalyst development to reactor design.” Chemical Engineering Journal 310(2): 537-559.