Ag/CN/ZnIn_(2)S_(4) S型异质结等离子体光催化剂的制备及其增强光还原CO_(2)研究

Fabricating Ag/CN/ZnIn_(2)S_(4) S-Scheme Heterojunctions with Plasmonic Effect for Enhanced Light-Driven Photocatalytic CO_(2) Reduction

S型异质结在电子的激发和输运方面具有优异的表现。本研究采用光沉积和水热法制备了Ag/CN/ZnIn_(2)S(ACZ)S型异质结复合光催化剂,其中,ACZ-60的CO和CH_(4)产率最高,分别为5.63μmol·g^(-1)和0.23μmol·g^(-1),是CN的6.5倍和2.1倍。通过电子自旋共振(ESR)和紫外光电子能谱(UPS)的表征分析,得出ACZ遵循S型电子转移路径的结论,进一步通过光电化学和PL测试证明S型异质结的形成改善了原本单体催化剂电子空穴复合率高的问题,同时也增强了光吸收。另一方面,沉积在CN表面的Ag NPs既作为反应活性位点,又具有等离子效应,进一步增强了对可见光的吸收性能,有效提升了电子传递效率,同时为反应提供了更多的热电子。此外,通过原位红外解释了光催化还原CO_(2)可能的反应路径。本研究为设计具有等离子体效应的S型异质结光催化剂提供了新思路。

As a higher oxidation state compound of carbon,more electrons and protons are needed to reduce CO_(2).While the step-scheme(S-scheme)heterojunction driven by semiconductors performs excellently in the excitation and transport of electrons,which has strong redox ability while inhibiting electron hole recombination,and has exhibited excellent results in photocatalytic CO_(2) reduction.Herein,Ag/CN was prepared by an optical deposition method,and the Ag/CN/ZnIn_(2)S_(4) S-scheme heterojunction composite photocatalyst was prepared by a hydrothermal method.The crystal structure,morphology and elements valences of the materials were analyzed using X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and other characterization methods,and the composite of the monomer was successfully verified.According to the electron spin resonance(ESR)and ultraviolet photoelectron spectroscopy(UPS)studies,formation of the S-scheme heterojunction was observed.Based on photoelectrochemical results and photoluminescence(PL)studies,the enhanced CO_(2) reduction can be attributed to the S-scheme electron transfer at the interface,which promotes charge separation.In the S-scheme electronic transmission system,CN acts as the reductive photocatalyst(RP)and ZnIn_(2)S_(4) as the oxidative photocatalyst(OP).Owing to the difference in Fermi energy levels,the electron cloud density changes until the Fermi levels match after contact between the RP and OP.This process generates internal electric fields and band bending at the interface,facilitating hole separation and the transfer of photo-induced carriers and photogenerated electrons.The plasmonic effect of the interfacial Ag NPs of the composite was proven using UV-Vis diffuse reflectance spectroscopy(DRS).When exposed to light,Ag NPs,as reactive sites of the reaction,act as receptors for electron transport.The excitation of high-energy thermal electrons on the surface of Ag NPs leads to the generation of localized electromagnetic fields between CN and Ag NPs,which subsequently accelerates the electron transport rate on the CB of CN and enhances light absorption,thus improving the photoreduction performance of hybrid materials.Under the combined action of the S-scheme heterojunction and plasmonic effect,the interface carrier transfer efficiency can be improved.Finally,the charge transfer mechanism was analyzed.Simultaneously,the possible reaction paths of photocatalytic CO_(2) reduction were explained by comparing the in situ Fourier-transform infrared spectroscopy(FT-IR)spectra of the monomer and compound.The CO_(2) reduction capability of composite materials was better compared to that of monomer materials.The best yields of CO and CH_(4) of ACZ-60 were 5.63μmol·g^(−1) and 0.23μmol·g^(−1),which were 6.5 and 2.1 times that of CN,respectively.Across four cycles,the CO and CH_(4) yields and XRD patterns of ACZ-60 showed excellent stability.This study provides a scheme for the rational design of photocatalytic CO_(2) reduction S-scheme catalysts.