Preparation Of Stabilized And Efficient Cu-based Nanocomposite Materials Toward Utilization In Solar Energy

The increasing demand for clean energy has sparked strong interests in the development of solar energy utilization.In recent years,metal-induced photocatalysis（Au,Ag and Cu）and solar-driven water evaporation have attracted tremendous attention by virtue of its great promise in photochemical conversion and plasmonic photothermal effects.However,most of these studies focused on Au（or Ag）,while the scarcity of precious metals severely limit their application.As a promising candidate,low-cost Cu NPs possess relatively low interband transition threshold and more broad plasmonic light-harvesting.However,the easy oxidation of Cu-based composite catalyst restricts its photocatalytic and solar vapor applications.In this work,by focusing on the challenge faced by the above Cu-based materials,Cu was selected as the main research object and a series of highly stable and efficient Cu based nanocomposites were prepared.The main results are as follows:1.Graphene-coated metal Cu nanoparticles（NPs）are fabricated through a two-step pyrolysis process using Cu-based metal organic framework as precursors for photocatalytic H₂ evolution.The results of TEM,Raman and XPS show that ultra-thin graphene can effectively inhibit the oxidation of Cu nanoparticles.Benefiting from the nanostructure,the optimized Cu@C/Sr Ti O₃ shows a photocatalytic H₂ evolution rate of 255.3μmol·g^-1·h^-1 and 21-fold activity enhancement compared with that of Cu/Sr Ti O₃ for isopropanol photodegradation under visible light.It is also found that charge redistribution can increase the electron density on the surface of graphene,which makes it show quasi-cocatalyst effect.2.On the basis of the above work,a composite catalyst of nitrogen-doped ultrathin graphene coated Cu nanoparticles with Sr Ti O₃ was designed and synthesized to solve the challenge of slow kinetics of photocatalytic water oxidation.The O₂ evolution of optimized catalyst with 1%Cu loading reached 308μmol g^-1·h^-1 under visible light,which was even comparable to that of Bi VO₄ prepared by hydrothermal method.The relationship between nitrogen doping and catalytic performance was studied by kinetic experiments and theoretical simulation.The reason for the improvement of activity is not only that the nitrogen-doped ultra-thin graphene layer improves the carrier separation efficiency,but also decreases the apparent activation energy of photocatalytic water oxidation.The thermal catalysis of the reduction of 4-nitrophenol shows that the catalyst has a good degradation performance.3.In order to make better use of plasmonic localized heating effect of Cu NPs,we designed a device of carbonized loofah sponges and multi-layer carbon-coated Cu for solar vapor generation.The device with stabilized Cu demonstrates a excellent light absorption（99%）in a wide solar spectrum range（300-2200 nm）.The localized heating effect of LSPR increases the interface temperature to 72°C,which effectively enhances the evaporation process and improves the vapor efficiency of solar energy.Moreover,3D porous micro-channels structure effectively improve water transport capacity of the device.This work is of great significance for the design and application of solar water evaporation devices using the localized heating effect of stablized Cu.