**5. Summary and outlook**

oxide (RGO).

environment. In addition, it shows significantly increased photodegradation performance even without a noble‐metal cocatalyst, which is due to the increased charge separation, visible‐light absorbance, specific surface area and reaction sites upon the introduction of MoS2 QDs. Besides, the enhancement mainly came from holes left in the TiO2 crystals rather than electrons transferring to reduced graphene **Summary and outlook** Photocatalysis appears to be a promising avenue to solve environmental and energy issues in the future. Although the photocatalytic processes involve a complicated sequence of multiple synergistic or competing steps, the efficient utilization of solar energy (especial visible-light energy) and improvement in separation and transportation of charge carriers are the main challenges and current trend to design highly effective photocatalysts. Finally, we conclude that this chapter, after discussing with various materials and its composites for photocatalytic process, may be useful for further applications in the area of energy and environment. In summary, we have discussed the general strategies and recent progress in photocatalysis for developing highly efficient and stable photocatalysts, including: (1) Titania (TiO2), iron oxides (α-Fe2O3); (2) ternary oxide photocatalytic matericals, such as Bi systems photocatalytic materials and (3) semiconducting materials and its composites. The achieved progress in photocatalysis indicates a promising route to enhance the photocatalytic efficiencies of photocatalytic semiconductors.

 Photocatalysis appears to be a promising avenue to solve environmental and energy issues in the future. Although the photocatalytic processes involve a complicated sequence of multiple synergistic or competing steps, the efficient utilization of solar energy (especial visible‐light energy) and improvement To date, in addition to different kinds of semiconductor materials and its composites significant advances have been reported to improve the photocatalytic efficiencies that range from environmental remediation to clean−energy harvesting by enhancing the utilization of sunlight or improving the separation/transportation of the electron−hole pairs some examples

in separation and transportation of charge carriers are the main challenges and current trend to design

highly effective photocatalysts. Finally, we conclude that this chapter, after discussing with various

materials and its composites for photocatalytic process, may be useful for further applications in the area

of energy and environment. In summary, we have discussed the general strategies and recent progress

in photocatalysis for developing highly efficient and stable photocatalysts, including: (1) Titania (TiO2),

are highlighted in this chapter. Extending light-response to the visible− or even infrared regions, decreasing the amount of recombination of electrons and holes, and increasing the light−harvesting efficiency have been the major tools that have led to such advances. Although great advancements have been made in investigation of heterostructured photocatalytsts, it is still challenging to design more challenges in high efficiency of photocatalytic systems. First, there is no detailed understanding of the charge generation, separation and transportation across nanoscale interfaces of heterostructured photocatalysts, which are critical for the design and optimization of highly more-efficient and more-reliable photocatalysts. Second, while most available photocatalysts so far can only function in the UV or near−UV regime, the highly effective utilization of visible light is another challenge of heterostructured photocatalysts. Third, photostability of heterostructured photocatalyst is and will still be a major challenge for practical applications. Finally, elucidating and understanding the mechanisms that are involved in various photocatalytic reactions. Therefore, the deepening knowledge of the photocatalytic mechanism and exploration of new materials are indispensible to make substantial breakthroughs for practical application of photocatalysts.
