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

Abstract

For excellence in the synthesis of highly active metal and oxide catalysts, a newly emerging technique—laser 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.

Perspective of Surfactant‐Free Colloidal Nanoparticles in Heterogeneous Catalysis

“…Pulsed laser post‐processing (PLPP) strategies of support materials to prepare defect‐rich NPs is an emerging field in laser‐based synthesis research . The main goal is to understand and develop photon‐induced defect formation strategies and understand how different types and densities of defect sites contribute to the catalytic activity in different reaction scenarios.…”

“…The main goal is to understand and develop photon‐induced defect formation strategies and understand how different types and densities of defect sites contribute to the catalytic activity in different reaction scenarios. Despite the studies on single crystalline oxide surfaces and bulk materials as well as nanomaterials, no general mechanism on laser‐based defect generation in the liquid is available to date . From the present knowledge, the most important laser parameters determining defect formation in terms of electron excitation and occurring thermal stress during and after laser irradiation are: laser pulse duration, laser fluence, the particle mass‐specific laser energy dose and laser wavelength .…”

“…In turn, Zhang et al. covered the recent advances, opportunities and challenges of laser‐material interaction during laser ablation with respect to the generation of defect‐rich or doped semiconductors for photo‐ and electrocatalytic applications . In two subsequent reviews, the Ma group first reviewed the utilization of laser‐generated metal and alloy nanoparticles at the example of carefully selected catalytic studies .…”

Reactivity of Trapped and Accumulated Electrons in Titanium Dioxide Photocatalysis

“…Facile laser ablation and processing techniques have been developed to introduce the defects into TiO 2 nanocrystals and colloids in liquid [31][32][33][34]. In a typical procedure, TiO 2 suspensions are irradiated by a high-intensity pulsed laser with frequent repetition rates to produce the characteristic blue-black TiO 2 .…”

Facile Formation of Stable Water‐Dispersed Luminescent Silicon Nanocrystals by Laser Processing in Liquid: Toward Fluorescent Labeling for Bio‐Imaging

“…Furthermore, the structural properties and composition of nanomaterials synthesized by this process can be controlled through external fields such as temperature‐ and electric‐fileds . It should be noted that the laser irradiation technique efficiently generates surfactant free nanoparticles which can exert an high catalytic activity . For the luminescent silicon nanoparticle formation, such a laser irradiation process is a promising top down approach .…”