Study On The Electrochemil Luminescence Behavior Of Luminol Cathode Catalyzed By Single-atom Hydrotalc-based Composites

Luminol is one of the most commonly used electrogenerated chemiluminescence（ECL）reagents due to its non-toxicity and high quantum yield.In principle,luminol cathodic ECL has more negative excitation potential and a simpler emission mechanism in comparison to its anodic ECL.Such a limitation of the luminol cathodic ECL is mainly ascribed to the fact that luminol cannot be electrochemically oxidized at a negative potential,leading to the relatively weak cathodic ECL signals.However,the current applications of luminol are mainly focused on its anodic ECL emissions.To solve this problem,it is necessary to find highly efficient electrocatalysts to improve the cathode ECL signal.In recent years,single-atom catalysts（SACs）have attracted much attention in many catalytic fields due to their high atom utilization and well-defined active sites.The understanding of reaction mechanism and the structural design of high performance single-atom catalysts can be realized by regulating the coordination environment and electronic structure around the single-atom.In this work,we prepared layered double hydroxides（LDHs）supported single-atom metals and investigated the catalytic behavior of single-atom catalysts for luminol cathode ECL.We have further explored the electron-metal and support interaction（EMSI）,achieved the amplification of luminol cathode ECL signal by modulating the interface electronic structure,and deepened the understanding of the interface effect between metal and support.In addition,a new method for the characterization of d-band center is established by using luminol cathode ECL signal.Specific research contents are as follows:1.An Ag single-atom catalyst with oxygen bridge interface（Ag-O-Co）was prepared by electrodepositing Ag on Co Al LDH modified indium tin oxide（ITO）electrodes（Ag^s/LDH/ITO）.Ag^s/LDH/ITO significantly enhanced luminol cathode ECL compared to the modified electrodes(LDH/ITO,Ag^np/LDH/ITO,Ag^np/LDH/ITO).According to the mechanism analysis,the improvement of ECL signal is attributed to the electronic structure of Ag-O-Co interface,which enhances the activity of oxygen reduction reaction（ORR）and fully activates oxygen through four-electron pathway,promoting the generation of reactive oxygen radicals（ROSs）.Moreover,the electron distribution of Ag and Co double metal sites can accelerate the electron transfer at the interface.Finally,improving luminol cathode ECL emission.This study provides a new idea for exploring the interface effects between the single-atom metal and support,and opens a new approach for improving luminol cathode ECL.2.Successfully prepared Co Al LDH-supported single-atoms Ag,Au indium tin oxide modified electrodes（Ag^s/LDH/ITO,Au^s/LDH/ITO）with different d-band centers to promote the luminol cathodic ECL.Contrast by phenomenon,the enhanced luminol cathode ECL signal on the Ag^s/LDH/ITO electrode was approximately 3.6 times that of the Au^s/LDH/ITO electrode.The mechanism study shows that the d-band center of Ag single-atom is closer to its Fermi level,which enhances the adsorption capacity of oxygen on the electrode surface and the activity of ORR,and promotes the formation of O₂^·-through the four-electron reaction pathway,then finally improves the ECL signal of luminol cathode significantly.This work established a direct relationship between the luminol cathode ECL performance and the d-band center.In addition,this study developed a novel strategy for characterizing the position of single-atom metal d-band center via cathode ECL signals.