Au-loaded ZIF-8 derived porous carbon with improved photothermal catalysis ability from interfacial heating instead of hot-electrons

Abstract

Photothermal catalysis has attracted increasing attention due to the efficient utilization of sustainable solar energy and high catalytic activity. However, its practical application is still limited due to the complex synthesis and low surface area of photothermal materials, as well as the challenges of distinguishing the effects of hot electrons and localized heating. To solve these issues, ZIF-8 derived porous carbon (ZPC) nanocrystals were constructed as high surface area photothermal materials and then decorated with Au nanoparticles as the catalytic components. Au/ZPC nanocomposites are prepared by the assembly of ZIF-8, the pyrolysis and in-situ Au reduction process. They are composed of rhombic dodecahedron-shaped ZPC with an average diameter of ∼120 nm, where Au nanoparticles (2–8 nm) are dispersed well on the surface or within the pore structure of ZPC. Besides, Au/ZPC exhibits a wide range of light absorption between 200 and 1100 nm and high photothermal efficiency of 45 %. With 4-nitrophenol (4-NP) reduction reaction as a model system, Au/ZPC catalyst exhibits a 2-fold increase in the rate of 4-NP reduction when exposed to an 808 nm laser irradiation, in comparison to thermocatalysis at the same temperature. Furthermore, the activation energy for the reduction of 4-NP via photothermal catalysis was much lower than that of thermocatalysis (74.16 vs. 104.26 kJ mol−1). By excluding hot electrons effects by transient absorption (TA) spectra, we can establish that the increase of photothermal catalysis rate should result from the localized heating which can decrease the energy barriers for the reduction of 4-NP. Additionally, Au/ZPC displays high stability and maintains remarkable activity even after five cycles. This study may provide some new perspectives for the design and development of efficient photothermal catalysts.