Controllable Synthesis And Study On Catalytic Property Of Au-Ag/Ag₂S Heterojunction Nanorods

Photocatalytic hydrogen evolution and electrochemical CO₂ conversion to useful carbon-based fuels are attractive strategies to alleviate environmental change and energy shortages.However,at present,the photocatalysts studied are usually unable to efficiently utilize sunlight and difficult to realize the adjustable optical properties.Electrocatalytic catalysts for CO₂ reduction are also faced with the problem of poor selectivity and difficulty in obtaining ethanol and other polycarbonate products.However,one-dimensional?1D?metal/metal or metal/semiconductor heterojunction nanomaterials are widely used in various catalytic reactions due to their high specific surface area and superior electron transfer properties,which can significantly enhance the activity and selectivity of catalytic reactions.At the same time,1D heterojunction nanomaterials can effectively regulate the optical response by controlling their length or aspect ratio,providing a prerequisite for wavelength selective catalysis.Introducing semiconductor on the surface of one-dimensional metal heterojunction nanomaterials to form a metal/semiconductor heterojunction can adjust the electronic structure of neighbouring atoms to influence the energy barriers of the rate-limiting reaction intermediates,moreover,the synergistic effect between metal and semiconductor will make the interface display unique chemical properties.In this paper,Ag-Au-Ag heterojunction nanorods?HJNRs?were firstly synthesized,and then Au-Ag/Ag₂S HJNRs were obtained through the surface vulcanization reaction.Ag-Au-Ag and Au-Ag/Ag₂S HJNRs were prepared for photocatalytic hydrogen evolution and electrocatalytic CO₂ reduction.Major results of this paper were as follows:1.We have for the first time developed a one-step aqueous-phase strategies to successfully synthesize well-defined and high-yield Ag-Au-Ag HJNRs with tunable lengths.The length of the nanorods could be controlled by controlling the reaction pressure,and the nanorods had adjustable longitudinal plasmon resonance peaks in the range of 500¹000 nm.The Ag-Au-Ag HJNRs can be further converted into Au-Ag/Ag₂S HJNRs by vulcanization reaction,which can expand the absorption range of sunlight.2.We have realized tunable wavelength-selective catalysis of Ag-Au-Ag HJNRs,which the best catalytic performance is obtained when irradiated with a wavelength light close to the plasma peak.Au-Ag/Ag₂S HJNRs had a broad solar energy harvest ability from³26 to¹100 nm and excellent electron-hole separation capacity,which exhibited superior hydrogen evolution property.For example,the Au-Ag/Ag₂S HJNRs have about 2.7-fold than those of Ag NWs.We further explored the photocatalytic activity enhancement mechanism of metal/semiconductor heterojunction from the photoelectric and photothermal perspectives by means of surface-enhanced Raman spectrum and I-t curves.3.Both Ag-Au-Ag and Au-Ag/Ag₂S HJNRs could reduce CO₂ to methanol and ethanol,and Au-Ag/Ag₂S HJNRs could significantly improve the ability of CO₂ reduction to ethanol,and the Faraday efficiency of ethanol can reach 74%.It is proved that Au/Ag,especially Au/Ag₂S interface,can promote C-C coupling and stabilize intermediate products by constructing different interfaces for comparison and density functional theory calculation,providing a key condition for the generation of ethanol.