The Research On Au Nanoparticles Plasmonic-enhanced Photocatalytic Water Splitting For Hydrogen Evolution

In recent years,energy shortage and environmental pollution have become two major social problems,seriously affecting human health and social development.Hydrogen（H₂）as a sustainable and pollution-free clean energy has been widely concerned.But it is another challenge to produce H₂cleanly and sustainably.The solar-driven water splitting into H₂is attracted the attention of many researchers.Since 1972,researchers have developed a series of semiconductor based photocatalysts.However,most semiconductor photocatalysts have shortcomings such as poor visible light response and poor stability,so various strategies and materials are used to improve the performance of photocatalysts.Among them,plasmonic metal nanoparticles（PNPs）/semiconductor photocatalysts are notable adjustable light response and ability to inhibit photoelectron-hole pair recombination by forming Schottky junctions.Therefore,it is greatly significant to design and synthesize PNPs/semiconductor nanocomposites reasonably.In this paper,PNPs/semiconductor nanocomposites are synthesized by seed growth method,hydrothermal method,high-temperature calcination method.The effects of growth conditions on gold nanoparticles（Au NPs）,the reaction mechanism of the Au NPs/g-C₃N₄system,and the structure of platinum-metal organic framework-gold（Pt-MOF-Au）nanocomposites on the activity of photocatalytic H₂production are studied.The detailed experimental results are as follows:1.Au NPs with different morphologies are synthesized by the seed growth method.The effects of growth conditions on the size and purity of Au nanorods（NR）are investigated.It is found that seed liquid,silver ion concentration,ascorbic acid（AA）,and p H value had a great influence on the morphology,size,and purity of Au NRs.The experimental results show that increasing the amount of seed solution could reduce the diameter of Au NRs,and increasing the concentration of silver ion could increase the aspect ratio of Au NRs to a certain extent.Appropriately reducing p H value is beneficial to the growth of Au NRs with a larger size,and excessive AA would make the morphology of Au NRs grow to the shape of the bone.2.g-C₃N₄nanosheets are synthesized by high-temperature calcination and ultrasonic stripping,then the pre-synthesized Au NPs are loaded onto g-C₃N₄by impregnation method,and the excess organic ions on Au NPs are removed by oxygen plasma treatment.The photocatalytic H₂production ability of Au NPs/g-C₃N₄nanocomposites in different spectral ranges is investigated,and the reaction mechanism is proved.The results show that Au NPs can act as both plasma and cocatalyst in local surface plasmon resonance（LSPR）enhanced photocatalyst.Whenλ>420 nm,the H₂production rate of Au NPs/g-C₃N₄reaches 159.9μmol g^-1h-1.3.Three-component Pt-MOF-Au nanocomposites with different loading modes are synthesized by the solvothermal method,including MOF,MOF/Au,MOF/Pt,Pt/MOF/Au,Pt@MOF,Pt@MOF/Au,and their photocatalytic H₂production ability in different light ranges are investigated.The photocatalytic H₂production rate of Pt@MIL-125/Au is higher than that of Pt/MOF/Au with the same load due to the structure of Pt@MOF/Au,the Schottky junctions of Pt-MOF and Au-MOF,and the LSPR effect of Au,which make it more favorable for the diffuse of light to inhibit the recombination of photoelectron-hole pairs.It shows that Pt@MOF/Au nanocomposites can more effectively promote the separation of photoelectron-hole pairs and prolong the life of carriers.