Preparation Of Graphene Two-dimensional Material On Au Single Crystal Surface And Its Study On Interface Electrochemical

As the traditional fossil energy consumption intensifies,the development of advanced materials for storing green energy has become a hot research field.As a novel type of two-dimensional material,graphene has high specific surface area,high electrical conductivity,favorable thermal stability and excellent mechanical properties.As a result,graphene has broad application prospects in integrated circuits,new energy and many other fields.However,most graphene-based materials tend to have complex and diverse structures with poorly defined nano-information.It is difficult to truly clarify the role of graphene in various fields,especially in complex electrochemical environments.Therefore,it remains a huge challenge to construct a modeled graphene electrodes and deeply explore the graphene-electrolyte related interfacial electrochemical information.In this paper,inert Au single crystal electrode was selected as the growth substrate of graphene two-dimensional materials,and graphene-materials/Au single crystal composite electrodes were constructed.The constructed graphene-material/Au single crystal composite electrode was taken as a model electrochemical research carrier,and its interfacial electrochemical properties in different electrolyte systems was investigated by the combination of traditional electrochemical cyclic voltammetry（CV）and in situ electrochemical scanning tunneling microscopy（EC-STM）techniques.The main contents of this paper are as follows:（1）Graphene was prepared on Au（111）and Au（100）single crystal electrodes through atmospheric pressure chemical vapor deposition（AP-CVD）device,which was self-designed based on the principle of inductively coupled heating.Raman spectroscopy confirmed that the obtained graphene was high-quality monolayer graphene.STM further revealed that the growth of graphene was controlled by the crystal face.The graphene-covered Au（111）substrate maintained the herringbone reconstruction of Au（111）-（22×√3）formed after thermal annealing,while the graphene-covered Au（100）substrate maintained the（hex）reconstruction.At this time,graphene formed the quasi-1D graphene striped superlattices under the control of the Au（100）-（hex）reconstructed crystal face;CV research found that the surface was covered with graphene,the unique reconstruction lifting and anion adsorption phase transition characteristics of Au（111）were almost completely covered.And the graphene coverage on Au（111）was determined to be 93.15%;In 0.1 M H₂SO_4,in-situ EC-STM revealed,the Au（111）herringbone reconfiguration was maintained over a wide potential range until the graphene was severely oxidized.And the oxidation occured preferentially at the graphene grain boundaries.The study also found that the addition of a trace amount of Cl^-would cause the Au（111）herringbone reconstruction to lift prematurely,while the oxidation still preferentially occurred at the graphene grain boundaries.（2）The graphene/Au（111）electrode was transferred to the non-aqueous ionic liquid HMim-FEP to study its interfacial electrochemical behavior different from that of bare Au（111）electrode.CV and in-situ EC-STM revealed the worm-like etching on Au（111）due to the adsorption of the cationic HMim⁺at negative potentials,as well as ionic liquid decomposition promoted the Au（111）surface healing at more negative potentials.However,for graphene/Au（111）,in-situ EC-STM observed the disappearance of reconstruction,graphene etching and exfoliation behaviors on its surface during the process of negative potential shift,confirming the anti-ionic liquid etching effect of graphene on Au electrodes.It also supplemented the EC-STM imaging information for the electrochemical study of the graphene-ionic liquid interface.（3）Using N-doped graphene/Au（111）as the electrochemical research model,the electrodeposition behavior of Cu and Pt on the graphene was inves tigated by CV and in-situ EC-STM.The electrochemical results revealed that the underpotential deposition（UPD）process on bare Au（111）disappear ed due to the prescience of covering nitrogen-doped graphene monolayer,while only the overpotential deposition（OPD）of Cu on graphene occured.In-situ EC-STM results further revealed that the nucleation of Cu preferentially taken place at the wrinkle sites of nigrogen-doped graphene and the growth of Cu deposit further follow ed the direction of distributed wrinkles.In addition,the electrodeposition process of Pt on N-doped graphene was also investigated.Unlike the steps and edges on bare Au（111）as nucleation sites,the deposition sites of Pt on N-doped graphene were randomly distributed and had greater dispersion.