Recently, in collaboration with Prof. Huang Jun from the University of Sydney, our group reported the construction of hollow-structured nano-photoreactors with bimetallic catalysts loaded within mesoporous silicas (AuPt@HMZS). This nanoreactor exhibited broader absorbance region under visible light and excellent catalytic activity in cinnamyl alcohol oxidation to cinnamic acid with 99% selectivity. The results were published on Natl. Sci. Rev.
Schematic diagram of hollow nanoreactors for photocatalytic oxidation of cinnamyl alcohol (Image by TIAN Hao)
Photocatalytic oxidation process has been considered as a sustainable technology to achieve the selective oxidation under ambient conditions with irradiation from solar light. To develop superior photocatalysts with a broad-range of light absorption and efficient electron-hole separation, surface modification with metal nanoparticles such as Au and Pt allow for the fast transfer of photoexcited electrons to the surface active sites. Therefore, bimetallic Au and Pt catalysts would be desirable by combining the advantages of both surface plasmonic resonance effect on Au and activation effect on Pt to further enhance the efficiency for catalytic oxidation under visible light irradiation. Moreover, hollow structured materials have shown great potential in a variety of applications, including catalysis, drug release and delivery, and energy storage and conversion. However, it remains great challenge to develop a facile and mild synthetic method to simultaneously create efficient hollow photocatalytic nanoreactor with ordered porous channels on the shell, well-controlled metal location, broad-spectrum utilization and well-controlled mass transfer and diffusion.
Scientists proposed a facile method to synthesize hollow-structured photocatalysts with controllable spatial location of active metals, chemical compositions and tunable shell thickness. Hollow nanoreactors can be constructed through coating SiO2 on the surface of ZIF-8 and a subsequent hydrothermal treatment. The formation mechanism of hollow structure is systematically investigated and a “adhesive-contraction” model is proposed. AuPt@HMZS nanoreactors has the following advantages: i) Broader absorbance region under visible light; ii) Multiple light scattering can be generated within a hollow void to enhance light-harvesting process and heat generated by the photo-thermal effect is collected; iii) The uniform channels are excellent to facilitate the reactant diffusion and mass transfer; iv) A synergetic effect among plasmonic hot electron injection and electron trapping improves solar energy utilization and electron-hole separation of photocatalysts; v) The strong metal-metal interactions at the alloy interface tune the reaction performance. The proposed strategy to build hollow structures as multifunctional micro/nanoreactors is promising for the design of high-performance and sustainable catalysts for chemical synthesis.
