Great Country Academician

The industrialized mass production of graphene is actually not a problem today.

Graphite oxide reduction method, micromechanical exfoliation method, chemical vapor deposition method, epitaxial growth and other methods have actually achieved a certain degree of mass production.

However, the graphene produced by these methods is not of high quality on the one hand, and on the other hand, the graphene produced is highly polluted.

For example, in the graphene oxide reduction method, the prepared graphene needs to be reduced at high temperature. In this process, incomplete reduction will lead to the coexistence of graphene and graphene oxide, and will also lead to the doping of other impurities in graphene.

However, if a vacuum furnace is used for reduction, the cost is too high.

This has led to the fact that this method can only produce some low-quality graphene at present.

However, this type of graphene cannot be used in high-performance electronic devices, energy storage, medicine and other fields. Generally speaking, this type of graphene doped with impurities and pollution is mainly used in construction, adsorbents, seawater desalination, etc. , composite materials and other basic fields.

However, the demand for graphene in these fields is actually not large. After all, no matter how low-quality graphene is, it is still graphene, and the price is much more expensive than the technology and materials used in the original industry.

High-quality graphene is the field with the greatest demand.

Whether it is electronic devices, photosensitive elements or aerospace and other fields, the gap for high-quality graphene has always existed.

However, the industrial mass production of high-quality graphene is an extremely difficult field to solve.

No way, the production process of high-quality graphene is too complicated.

First of all, to manufacture high-quality graphene, it is necessary to prepare high-quality single-layer graphene.

At present, high-quality single-layer graphene is almost limited by the cavity size of CVD equipment, and the existing CVD method cannot achieve continuous preparation of single-layer graphene.

Although in this field, a country that has begun to secretly discharge nuclear sewage into the sea has demonstrated a so-called 100-meter-long graphene, the surface of the material has many holes and is completely unusable.

Moreover, the continuous preparation technology and product yield of CVD graphene have not been solved yet.

Secondly, the high-quality graphene transfer method is a difficult problem to solve. The commonly used wet etching transfer method often brings problems such as wrinkles, impurities, and damage, and it is difficult to achieve large-scale transfer.

The last is a combination of the former two.

That is to realize the continuous preparation and transfer of CVD graphene, and the two are matched and docked to form an automated production technology.

When the first two difficulties are not resolved, it can be said that there is no way out for high-quality graphene manufacturing.

In fact, how to evaluate a new technology, especially the technology of materials science, is not easy in itself.

It requires a lot of supporting conditions.

In fact, many achievements in material science and technology need to spend half of the energy on the pure application testing behind.

And this studio requires a lot of investment. Without sufficient capital support and downstream application support, it is basically useless.

Although graphene has the support of downstream manufacturers, its manufacture and application is a very difficult problem.

That's why Xu Chuan is very interested in the mass production of high-quality graphene developed by the Chuanhai Materials Research Institute.

"Go to my office and talk about it. The results of the experiment here will not come out until around three o'clock in the afternoon, but I roughly sorted out the relevant production methods and steps yesterday."

Fan Pengyue took off his experimental gloves and brought Xu Chuan to his office.

Turning on the computer, unlocking it, he called up a document from the computer, clicked on it and said: "I haven't had time to print out the document, so you can use the computer to look at it first."

Xu Chuan didn't care, took the seat and sat down, carefully flipping through the documents in front of him.

From the data point of view, this method of preparing high-quality graphene is expanded from the method of recycling graphite to prepare graphene from the LIBs battery that was accidentally discovered in the second half of 2019.

In 2019, a researcher named 'Yan Liu' in the lithium-sulfur battery laboratory of the research institute used materials such as hydrazine hydrate, molten salt hydroxide, and aluminum foil of the positive electrode waste current collector as reduction materials when further optimizing the lithium battery. agent, trying to modify the LiFePO4 positive electrode to improve the electrochemical performance and cycle stability of lithium batteries.

However, the expected optimization was not achieved, but unexpectedly, during the production test of the failed product, Yan Liu found a layer of carbon film attached to the negative electrode.

After testing, it was confirmed that this is a layer of relatively high-purity graphene film material.

In this new chemical synthesis method, after the graphite negative electrode undergoes electrochemical cycles, it undergoes chemical oxidation to obtain uniformly dispersed graphene oxide.

Then, the graphene oxide is reduced to graphene through the use of oxidizing and reducing agents.

The graphene synthesized in this way is relatively pure and pollution-free.

Of course, it also has many disadvantages.

For example, the reduction of graphene oxide involves the use of environmentally unfriendly and expensive oxidants and reducing agents, and the chemical reaction will also destroy the integrity of the graphene film material structure.

In addition, the transfer of graphene is also extremely difficult.

There are many shortcomings, but this is still a direction worth exploring.

This incident caught Xu Chuan's attention at that time, but at that time, because he was busy with the controllable nuclear fusion project, he couldn't spare time for in-depth research, so he could only hand over this matter to Chuanhai Materials Research Institute Own.

More than a year and a half later, combined with the Institute's computational material model, this method of synthesizing high-purity graphene film materials has been greatly improved.

As we all know, there are three difficulties in the synthesis of high-quality graphene.

From the continuous synthesis of high-purity monoatomic layer graphene layers to the transfer of thin films, and continuous industrialization are extremely difficult things.

After a year and a half of exploration, the Materials Laboratory has improved this new electrochemical synthesis method.

The first is to further optimize the high purity of graphene, the negative electrode material of the original LiFePO4 battery.

Use high-purity synthetic graphite with a purity of more than 99.999% to replace the original graphite material for the negative electrode of the battery.

After all, although the negative electrode of LiFePO4 battery uses graphite, in order to improve the performance of the battery, it is not high-purity graphite and contains impurities.

Although the amount of these impurities is not much, they will also affect the quality of graphene in the process of synthesizing graphene.

Of course, this is not the key.

The key problem of this electrochemical synthesis of graphene is the need for redox and the transfer of the synthesized graphene.

The latter is still easy to solve, whether it is external microwave transfer or liquid phase stripping method, but the efficiency is not high, and there will be problems such as defective products.

The former, for the reduction of graphene oxide, has always been a difficult problem in the industry.

Although there are many choices of reducing agents for graphene oxide, from hydrazine and hydrazine derivatives, to metal hydrides such as sodium borohydride, strong acids, strong bases, alcohols, phenols, vitamin C, reducing sugars (glucose, chitosan, etc.) sugar, etc.) etc. can do.

But no matter which one it is, it has its own shortcomings.

For example, the use of some acid to restore graphene will lead to the agglomeration and accumulation of the single-layer graphene structure due to the π-π interaction, resulting in a decrease in the specific surface area, an increase in resistance, and a significant decrease in performance.

This limits its application prospects.

Or use hydrazine or hydrazine derivatives for reduction. Although the obtained graphene solves the agglomeration phenomenon of the product, it also introduces C-N bonds into the reduced graphene, causing pollution.

Moreover, the hydrazine hydrate used is highly toxic and is not suitable for large-scale production, industry, and biomedicine.

So Xu Chuan is very curious about how Chuanhai Materials Research Institute solves this problem.

Following the documentation, Xu Chuan continued to look down.

In the summary of the reduction method of graphene oxide, he saw the way of reducing graphene oxide by Chuanhai Materials Research Institute.

". Use different film assembly methods to modify graphene oxide on a specific electrode substrate to obtain a graphene oxide modified electrode, and then use this modified electrode as the working electrode of the classic three-electrode electrolysis system in a specific electrolyte solution. Electrolysis reaction, so as to achieve the reduction of graphene oxide film."

"Electrochemical reduction method?"

Seeing this way, Xu Chuan was taken aback for a moment.

He originally thought that the laboratory had found a new type of reducing agent, but he didn't expect that they would break away from the limitation of the reducing agent and use an alternative electrochemical method.

[Sonicate graphene oxide in deionized water for 1 h, then modify it on a conductive glass substrate, and conduct extended cyclic voltammetry (CV, -1.0 to 1.0 V, relative to a reversible hydrogen electrode) at 0.1 mol/L The electrochemical reaction of Na2SO4 solution with Hg/Hg2SO4 and Pt electrodes as reference and counter electrodes in a standard three-electrode cell was used to reduce graphene oxide. 】

【Detect and control the reduction degree of graphene oxide by measuring the reduction peak and specific capacitance value at -0.75 V by X-ray photoelectron spectroscopy (XPS). 】

[Further cooperate with the electrochemical deposition method to modify graphene oxide on the conductive glass substrate, and then pair it with the glassy carbon electrode in a 0.1 mol/L solution, and scan at an intensity of 0 to -0.1 V, the substrate located on the substrate can be obtained. on the film. 】

【.】

The information is not very detailed, not even those electron microscope structure diagrams, but it is enough for Xu Chuan to understand how they did it.

It has to be said that this is a very clever way to find another way.

Nowadays, the reduction of graphene oxide and the preparation of graphene in the materials industry have been considering how to take advantage of reducing agents or catalysts.

Although methods such as microwave reduction, hydrothermal reduction, and catalytic reduction have been studied, these methods are not actually free from the limitations of reducing agents and catalysts.

And this method of electrochemical reduction directly bypasses the influence of reducing agents and catalysts.

Not to mention its efficiency, but without additives such as reducing agent and catalyst, the purity of the reduced graphene is undoubtedly quite high.

After all, in the process of reduction, he no longer has the influence of other foreign additives.

PS: There is another chapter in the evening, asking for a monthly pass. It's the end of the month, let's vote for the monthly tickets in the hands of the big guys! ~o(=∩ω∩=)m meow!

Thanks to the reader Dp for the continuous rewards, thanks to Cao Mianzi for the 1500 points reward, thanks to the 1500 points reward from Let the Flow 2023 boss, thank you Starry Sky Michael for the 100 points reward, and thank you Tang Moming for the 100 points reward , Thank you guys, meow(‵▽′)ψ