Synthesis Of Metallene And Its Electrochemical Properties

Since the twentieth century,there has been an increasing demand of various two-dimensional materials,including graphene,transition metal dichalcogenides,metal organic frameworks,layered double hydroxides and metallene.Studies on materials are gradually moving towards lower dimensions and controlling their morphological structure,which can lead to functional materials with different properties.In general,metal atoms are arranged in an orderly manner to form a three-dimensional structure.In contrast,metallene is a two-dimensional structure like graphene with several atomic layer thickness.Therefore,it is necessary to suppress the aggregation between layers and make them laterally grow along the plane.Therefore,a bottom-up synthesis strategy can be used to modulate the microstructure of the material using different preparation methods such as ligand confinement,template-mediated anisotropy,and topotactic reduction of layered materials.Nowadays,metallenes are widely used in electrocatalysis including oxygen reduction reaction(ORR),carbon dioxide reduction reaction(CO2RR),ethanol oxidation reaction(EOR),hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).The key aspect in the catalytic reaction is the interaction between the reaction substrate and the catalyst surface.Therefore,the size of metallene and the type of active center have a significant impact on the catalytic performance.Thus,designing catalysts with suitable size and active centers for various application systems often requires different synthetic strategies,such as chemical modification,polymetallic alloying,defect engineering,etc.With this consideration,unique functional materials can be achieved by changing the electronic structure of the materials.Based on the above background,we have successfully prepared ultrathin two-dimensional metallene materials by using a one-pot synthesis method.The synthesis of metallene was performed under low-temperature conditions using carbonyl compounds as reducing and structure-directing agents.The obtained metallenes are used as electrocatalysts for the reduction of nitrate to ammonia and glucose sensors.The details of the study are summarized as follows:1.Synthesis of PdMoCu trimetallene and the electrocatalytic activity for the reduction of nitrate to ammonia.PdMoCux trimetallenes with different doping amounts were prepared using one-pot synthesis approach and applied for the reduction of nitrate to ammonia.It was observed that the as-prepared trimetallenes are composed of ultrathin two-dimensional nanosheets,showing a highly folded shape with a large specific surface area.The EDS results show that it mainly contains four elements,Pd(66.56%),Mo(3.08%),Cu(2.51%)and C(27.85%).In terms of electrochemical properties,it has a larger electrochemically active area and faster electron transfer rate compared with PdMo bimetallene.Meanwhile,PdMoCu0.5 exhibited efficient NO3RR electrocatalytic activity,selectivity,and stability.At-0.6 V(vs.RHE),the NH3 yield was 250.4 μmol h-1 cm-2 with the corresponding Faraday efficiency of 56.95%.The isotopic labeling measurements demonstrated that the NH3 product originated from nitrate.The results show that the unique two-dimensional structure and the synergistic interaction between multi-atoms after appropriate amount of Cu doping could significantly improve the catalytic performance of the material.This work also illustrates that trimetallenes can be used as a promising catalyst in electrocatalytic ammonia synthesis.In addition,this study will also bring inspiration to the synthesis of metallenes for different electrocatalytic reactions.2.Synthesis of PdNi bimetallene for glucose electrochemical sensorsPdNi bimetallic alkenes was obtained by wet chemical synthesis method followed by addition of Ni atoms.The material has a smooth surface and uniform morphology,showing a folded two-dimensional thin layer structure.Meanwhile,the nanosheets are bent to each other,exposing more active sites.The EDS results showed that the surface mainly contains three elements,Pd(73.82%),C(22.48%)and Ni(3.7%).The catalyst ink was modified onto the surface of the glassy carbon electrode for the quantitative detection of small glucose molecules.A strong oxidation peak is shown in the CV curve,which verifies the feasibility of the experiment and demonstrates that the catalytic process is mainly controlled by the diffusion step.The sensor exhibited a high sensitivity(197.3 μA mM-1 cm-2)and a low detection limit(62.2 nM)for the quantitative detection of glucose by the i-t method at an operating voltage of 0.75 V.In addition,the sensor was found to have good selectivity,long-term stability,and interference resistance,which provides a new idea for commercialized enzyme-free assays.