Recent Advances in Surfactant-Free, Surface-Charged, and Defect-Rich Catalysts Developed by Laser Ablation and Processing in Liquids

For excellence in the synthesis of highly active metal and oxide catalysts, a newly emerging techniquelaser synthesis and processing of colloids (LSPC)-is gaining increasing attention for catalytic applications, such as water splitting, fuel cells, and photodegradation of organic pollutants. The advantages of using LSPC-synthesized metal catalysts have been reviewed elsewhere [Chem. Rev. 2017, 117, 3990-4103]. Herein, current challenges related to the properties (surface chemistry and particle evolution) of metal catalysts synthesized by laser ablation in liquids/laser processing in liquids are discussed. The main focus is on the advantages of LSPC in surfactant-free defect engineering of oxide nanoparticles. Compared with other techniques (e.g., hydrogenation), LSPC provides a unique platform to simultaneously introduce oxygen vacancies and surface disorders into oxide (e.g., TiO2) nanomaterials; thus allowing narrowing of the band gap from both conduction and valence bands. Defect-rich oxides have versatile uses, such as being directly applied as photocatalysts and as building blocks to construct supported, doped, and ternary oxide photocatalysts for electrochemical and photocatalytic applications. The LSPC-synthesized catalysts are promising for applications as commercial catalysts in light of their higher activities than those of current Pt/C and P25 TiO2 commercial catalysts.