TW201500592A - Method of removing and recycling conductive substrate from carbon layer - Google Patents

Abstract

A method of removing and recycling a conductive substrate from a carbon layer comprises electrochemical treatment and wet etching treatment. The electrochemical treatment provides electrolyte, conductor as the cathode and a workpiece to be treated which comprises a conductive substrate as the anode and a carbon layer adhered on the conductive substrate. When the conductive substrate and the conductor are in contact with the electrolyte, electric energy is provided to the conductor and the workpiece to be treated so as to electroplate a part of the conductive substrate onto the surface of the conductor. The wet etching treatment uses etchant to remove residual conductive substrate on the carbon layer to obtain the carbon layer. The method of this invention can not only recycle the conductive substrate but also obtain carbon layer with high quality.

Description

Method for removing and recovering a conductive substrate from a carbon layer

The invention relates to a method for removing and recovering the conductive base layer from a workpiece to be processed containing a conductive base layer and a carbon layer, in particular to a conductive base layer combined with electrochemical treatment and wet etching treatment. The method of removing and recovering a body from a carbon layer.

Graphene is widely used in soft products (such as flexible displays or solar panels) because it has high flexibility and the conductivity of graphene does not have any influence due to bending and winding. In various methods for preparing graphene, graphene prepared by chemical vapor deposition is formed on a substrate (such as a metal layer), so how to remove the substrate or how to transfer graphene has become One of the technologies that industry players are eager to develop.

Most of the removal of the substrate is performed by directly immersing the object to be treated containing the substrate and graphene in an etching solution, and dissolving the substrate through the etching solution to complete the removal of the substrate; however, this method causes loss of the substrate, The process time is long, and a large amount of etching waste liquid is generated to cause environmental pollution. In order to solve the aforementioned problems, today's multi-directional transfer to graphene Methods were studied.

"Repeated growth and bubbling transfer of graphene with millimetre-size single-crystal grains using platinum" published by Libo Gao et al., "Nature communication" in 2012, discloses an electrolysis method for separating a platinum-based layer body and graphene. It is a method for transferring graphene by electrolytic gas production.

The method provides an aqueous solution of sodium hydroxide, a platinum plate (Pt foil), and a member to be treated comprising a platinum substrate and a graphene film disposed on the platinum substrate. Taking the platinum sheet as an anode, the platinum base layer as a cathode, and contacting the platinum sheet and the platinum base layer with an aqueous sodium hydroxide solution, and applying electric energy to the platinum sheet and the platinum base layer body, at this time, Hydrogen is generated between the platinum base layer and the graphene, and the graphene is pushed by hydrogen to completely separate the graphene from the platinum base layer.

Although the method can completely separate the graphene from the platinum-based layer body without consuming the platinum-based layer body, the graphene obtained by the method can destroy the integrity of the graphene because the gas pushes the graphene. , resulting in poor quality of graphene. Meanwhile, because of the need to produce sufficient amount of gas, so that the platinum is completely separated from the base layer of the graphene material is required higher voltage (e.g., platinum base layer body area of 3 cm ^2, a required current density of at least 0.1 A / cm ² or more The voltage requirement is at least 5 V to generate a sufficient amount of gas), resulting in an increase in equipment threshold requirements and equipment costs. High voltage operation and the generation of large amounts of hydrogen and oxygen can also cause operational safety problems. In addition, the large amount of oxygen generated at the anode causes oxidative corrosion of the anode, which in turn seriously affects the stability of the anode.

As apparent from the above description, there are still various problems in the method of transferring graphene by electrolytic gas production. Therefore, how to reduce the damage of graphene during the transfer process to obtain a good quality graphene and at the same time recover the base layer is still the research and development goal that the industry is currently seeking.

Accordingly, it is an object of the present invention to provide a method for removing and recovering a conductive substrate from a carbon layer, which method not only recovers the substrate but also obtains graphene of good quality.

Therefore, the method for removing and recovering a conductive substrate from a carbon layer of the present invention comprises: (a) electrochemically treating, providing an electrolyte, an electrical conductor, and a member to be processed, the workpiece to be processed a conductive base layer, and a carbon layer attached to the conductive base layer, wherein the conductive body is used as a cathode and the conductive base layer is used as an anode, and the conductive base layer and the electrical conductor are in contact with the electrolyte, and The material to be processed and the electrical conductor are energized to partially electroplate the conductive substrate onto the surface of the electrical conductor; and (b) wet etching to deposit a conductive base layer remaining on the carbon layer with an etching solution The body is removed to obtain the carbon layer, wherein the etching solution may be the same as or different from the electrolyte.

The effect of the present invention is that, in combination with (a) electrochemical treatment and (b) wet etching treatment, not only the conductive base layer but also a carbon layer of good quality can be obtained.

The contents of the present invention will be described in detail below: [Electrochemical Treatment of Step (a)]: The arrangement between the electrochemically treated cathode, anode and electrolyte of the step (a) can be set according to a generally known manner.

The shape of the conductor may be linear, rod, sheet or mesh. The material of the conductor is not particularly limited as long as it does not react with the electrolyte and is not dissolved by the electrolyte, and can partially plate the conductive substrate to the conductor during electrochemical treatment. It can be on the surface. The material of the conductor is, for example but not limited to, stainless steel, graphite, platinum, titanium, niobium, tantalum, niobium, tantalum oxide, niobium oxide, copper, nickel, iron, zinc, a copper alloy, a nickel alloy, an iron alloy, a zinc alloy or the like. Among the materials listed above, copper, nickel, iron, zinc, copper alloy, nickel alloy, iron alloy and zinc alloy are dissolved in the electrolyte when used as an anode, but they are not protected by the electric field of the cathode when used as a cathode. It is soluble in the electrolyte and is therefore also suitable for use in the process of the invention.

The material of the conductive base layer is not particularly limited as long as it can be dissolved in the electrolytic solution during electrochemical treatment and plated on the conductor. Preferably, the conductive substrate is selected from the group consisting of copper, nickel, iron, cobalt, zinc, copper alloys, nickel alloys, iron alloys, cobalt alloys or zinc alloys.

The material of the carbon layer is not limited herein, and the material of the carbon layer may be used singly or in combination, such as, but not limited to, graphite, graphene, nano carbon fiber, carbon nanotube, fullerene, diamond-like carbon ( Diamond-Like Carbon, referred to as DLC).

The workpiece to be processed further includes a polymer layer disposed on the carbon layer. The material of the polymer layer is not particularly limited, and it is also not reactive with the electrolytic solution and is not dissolved by the electrolytic solution. The material of the polymer layer may be used singly or in combination, such as, but not limited to, polymethyl methacrylate, polyvinyl alcohol, polydimethyl siloxane, silicone, ethylene-vinyl acetate resin, polyethylene, polyphenylene. Ethylene or polypropylene. The electrolyte may be such that a part of the conductive substrate is plated on the surface of the conductor. The electrolyte is selected from a neutral electrolyte, an acidic electrolyte, or an alkaline electrolyte. The neutral electrolyte may be used singly or in combination, and the neutral electrolyte may be, for example but not limited to, a lithium salt-containing solution, a sodium salt-containing solution, a potassium salt-containing solution or an ammonium salt-containing solution. The lithium salt is, for example but not limited to, lithium sulfate (Li ₂ SO ₄ ), lithium chloride (LiCl), lithium nitrate (LiNO ₃ ), and the like. The sodium salt is, for example but not limited to, sodium sulfate (Na ₂ SO ₄ ), sodium chloride (NaCl), sodium nitrate (NaNO ₃ ), and the like. Potassium salts are, for example but not limited to, potassium chloride (KCl), potassium sulfate (K ₂ SO ₄ ), potassium nitrate (KNO ₃ ), and the like. The ammonium salt is, for example but not limited to, ammonium chloride (NH ₄ Cl), ammonium nitrate (NH ₄ NO ₃ ), or ammonium sulfate [(NH ₄ ) ₂ SO ₄ ] or the like. The acidic electrolyte is, for example but not limited to, a solution of sulfuric acid (H ₂ SO ₄ ), a solution of hydrogen chloride (HCl), a solution of perchloric acid (HClO ₄ ), a solution of phosphoric acid (H ₃ PO ₄ ), a solution of carbonic acid (H ₂ CO ₃ ). , hydrogen peroxide (H ₂ O ₂ ) solution or nitric acid (HNO ₃ ) solution, and the like. The alkaline electrolyte includes an alkaline electrolyte, a solvent, and a chelating agent. Since the ions of the conductive substrate body form a hydroxide passivation film or a precipitate in the alkaline electrolyte, the conductive substrate body cannot be plated on the surface of the conductor, so when the electrolyte is an alkaline electrolyte, it is necessary to add the Chelating agents to avoid this. The alkaline electrolyte can be used singly or in combination, such as, but not limited to, lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH) or ammonium hydroxide (NH ₄ OH). The chelating agent can be used singly or in combination, such as, but not limited to, citric acid or ethylenediaminetetraacetic acid (EDTA). The solvent may be dissolved in the alkaline electrolyte and the chelating agent, and the solvent may be used singly or in combination, such as, but not limited to, water. Preferably, the electrolyte is an acidic electrolyte.

The pH of the electrolyte ranges from 0 to 14. Preferably, the electrolyte has a pH in the range of 0 to 6. Preferably, the concentration of the electrolyte ranges from 1 mM to 6 M.

[Wet Etching Treatment of Step (b)]: The etching liquid is selected according to the material of the conductive base layer, as long as the conductive base layer can be etched and dissolved. The etching solution can be used singly or in combination, and the etching liquid is, for example but not limited to, a copper etching solution (for example, a copper etching solution made by Alfa Aesar, model: 44583), a nickel etching solution (for example, a nickel etching solution made of BASF, model number). : NPE-400 EC) and so on. In the electrochemical treatment, an electrically conductive etching solution can also be used as the electrolyte to accelerate the speed of the electrochemical treatment.

In the method for removing and recovering a conductive substrate from a carbon layer in the present invention, the conductive substrate is recovered by (a) electrochemical treatment by partially plating the conductive substrate onto the surface of the conductive body. The carbon layer is obtained by removing the conductive substrate remaining on the carbon layer by (b) wet etching. The method of the present invention can recover the conductive base layer and obtain a good quality carbon layer without (b) high operating voltage, non-destructive quality of the carbon layer, and (b) wet etching treatment.

The present invention will be further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

<Example> [Example 1] Electrochemical Treatment

Providing an electrolyte (copper etching solution made by Alfa Aesar, product model number: 44583), an electric conductor [material: cerium oxide, area: 3 cm × 5 cm, the weight recorded at this time is (W _a0 )], and waiting for The processing member [the weight at this time is recorded as the weight (W _b0 )], and the to-be-processed member includes a conductive base layer (material: copper, area: 1 cm × 3 cm), and is formed on the conductive substrate by vapor deposition. And a graphene layer having a thickness of less than 1 nm, and a polymethacrylate layer formed on the surface of the graphene layer.

Taking the electric conductor as a cathode, the conductive base layer is used as an anode, the electric conductor and the conductive base layer are in contact with the electrolyte, and an electrical energy is applied to the electric conductor and the conductive base layer (voltage: 1.2 V, Current: 0.2 A, current density: 67 mA/cm ² , power: 0.24 W) [When the electrical energy is applied, it is recorded as the starting time (t ₀ ) of the electrochemical treatment], at which time some of the conductive substrate gradually dissolves. In the electrolyte, and electroplated on the surface of the electrical conductor. When the current drops significantly (current: 0.01 A), the supply of electric energy is stopped [the end time (t ₁ ) of the electrochemical treatment is stopped when the electric energy is stopped], and the weight (W _a1 ) of the electric conductor at this time is measured, and The weight of the treatment piece (W _b1 ).

Wet Etching Treatment

After the electrochemically treated material to be processed is removed from the electrolyte, it is transferred to an etching solution (copper etching solution manufactured by Alfa Aesar, product model number: 44583). [When it is transferred to an etching solution, it is recorded as wet etching. Starting time (t ₂ )], at this time, the etching liquid gradually removes the conductive base layer remaining on the graphene layer, and the etching liquid layer completely removes the conductive base layer body [when the conductive base layer body is completely removed, it is recorded as wet The graphene layer was obtained by the end time (t ₃ ) of the etching treatment.

[Examples 2 to 5]

Examples 2 to 5 were carried out in the same manner as in Example 1, except that different electrolytes and electric energy conditions were used. The electrolyte used in Examples 2 to 5 was an aqueous solution of sulfuric acid (concentration: 0.5 M, which is referred to as sulfuric acid _{(aq.) in} Table 1), and the etching solution was a copper etching solution (copper etching solution manufactured by Alfa Aesar, product type) :44583).

The types of the electrolytic solution and the etching liquid used in the above Examples 1 to 5, and the electric energy conditions are shown in Table 1.

[Comparative Example 1] Wet etching method

A member to be processed is provided, which is the same as the member to be processed in Embodiment 1, and therefore will not be described again. The workpiece to be treated is brought into contact with an etching solution (copper etching solution manufactured by Alfa Aesar, product model number: 44583), and subjected to a wet etching treatment (referred to as a starting time t ₄ of the wet etching treatment), and the etching solution is to be a conductive substrate. After the body is completely removed [indicated as the end time (t ₅ ) of the wet etching treatment], the graphene layer is obtained.

[Comparative Example 2] Electrolytic gas transfer method

Providing an aqueous solution of sodium hydroxide as an electrolyte (concentration: 1 M, denoted as sodium hydroxide _{(aq.) in} Table 1), an electric conductor [material: cerium oxide, area: 3 cm × 5 cm], and The processing member is the same as the member to be processed in Embodiment 1, and therefore will not be described again.

Taking the electric conductor as an anode, the conductive base layer of the to-be-processed member serves as a cathode, the electric conductor and the conductive base layer are in contact with the electrolyte, and an electric energy (voltage is applied to the electric conductor and the conductive base layer) : 10 V, current: 15 A, current density: 500 mA/cm ² , power: 150 W) [When the electric energy is applied, it is recorded as the start time (t ₆ ) of the electrolytic gas transfer method], and there are bubbles at this time. It is produced at the conductor and the conductive substrate, and the graphene layer is completely separated from the conductive substrate [when the graphene layer and the conductive substrate are completely separated, it is referred to as the end time (t ₇ ) of the electrolytic gas transfer method].

[evaluation project]

Operation time

According to the following formula (1), the operation time of the examples 1 to 5 is obtained, and the unit is min.

Operation time of Examples 1 to 5 = (t _{1 -} t ₀ ) + (t _{3 -} t ₂ ) Equation (3)

Calculated according to the following formula (2), the operation time of Comparative Example 1 was obtained, and the unit was min.

Operation time of Comparative Example 1 = (t _{5 -} t ₄ ) Equation (2)

Calculated according to the following formula (3), the operation time of Comparative Example 2 was obtained, and the unit was min.

Operation time of Comparative Example 2 = (t _{7 -} t ₆ ) Equation (3)

2. Recovery rate

According to the following formula (4), the recovery of Examples 1 to 5 is obtained. Rate, unit: %.

Recovery rate = (W _{a1 -} W _a0 ) ÷ (W _{b0 -} W _b1 ) × 100% Equation (4)

3. Sheet resistance of graphene layer

The graphene layers obtained in the methods of Examples 1 to 5 and Comparative Examples 1 to 2 were measured for sheet resistance of the graphene layer by a four-point probe measuring instrument (manufacturer: Jandel model: RM3000), each graphene The layer takes the average of 10 points of data. The sheet resistance of the graphene layer is 700 ohm/cm ² or less, which can be regarded as excellent in quality.

The results of the above evaluation items are shown in Table 1.

As can be seen from the results of Table 1, the conductive substrate was completely incapable of being recovered by the wet etching method of Comparative Example 1, and the recovery of the conductive substrate of the methods of Examples 1 to 5 was 61% to 97%, which is more worth mentioning. Yes, the graphene layers obtained by the methods of Examples 1 to 5 still have good quality (sheet resistance value 510 to 660 ohm/cm ² ). Moreover, the operation time of the methods of Examples 1 and 3 to 5 was greatly shortened to 11 to 18 minutes as compared with the wet etching method of Comparative Example 1.

The sheet resistance of the graphene layer obtained by the electrolytic gas transfer method of Comparative Example 2 was as high as 1170 ohm/cm ² , and it was found that the electrolytic gas transfer method did seriously impair the quality of the graphene layer, in contrast, Example 1 to The graphene layer obtained by the method of 5 has excellent quality. In addition, compared with the electrolytic gas transfer method of Comparative Example 2, a higher voltage (10 V) is required, and the voltages of the methods of Embodiments 1 to 5 are only 0.4 V to 1.6 V, thereby avoiding the occurrence of high voltage operation. The problem of high security and equipment requirements.

In summary, the method for removing and recovering a conductive base layer from a carbon layer of the present invention can not only recover the conductive base layer but also can be recovered by the combination of (a) electrochemical treatment and (b) wet etching treatment. A carbon layer of good quality is obtained, and high voltage is not required for operation, so the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

Claims (5)

A method for removing and recovering a conductive substrate from a carbon layer, comprising: (a) electrochemical treatment, providing an electrolyte, an electrical conductor, and a member to be treated, the component to be processed comprising a conductive substrate, And a carbon layer attached to the conductive substrate, and using the electrical conductor as a cathode and the conductive substrate as an anode, contacting the conductive substrate and the electrical conductor with the electrolyte, and the workpiece to be processed And the electrical conductor is energized to partially electroplate the conductive substrate onto the surface of the electrical conductor; and (b) wet etching to remove the conductive substrate remaining on the carbon layer with an etching solution to remove The carbon layer is obtained; wherein the electrolyte and the etching solution may be the same or different. The method of claim 1, wherein the electrolyte is an acidic electrolyte. The method of claim 1, wherein the electrolyte has a pH in the range of 0 to 6. The method of claim 1, wherein the concentration of the electrolyte ranges from 1 mM to 6 M. The method of claim 1, wherein the conductive substrate is selected from the group consisting of copper, nickel, iron, cobalt, zinc, a copper alloy, a nickel alloy, an iron alloy, a cobalt alloy, or a zinc alloy.