Why Is Carbon Used As An Electrode?

In modern technology and industry, the selection of electrode materials is of vital importance. From the electrolysis industry to energy storage systems, carbon materials have always occupied a core position in electrode materials. But why can carbon stand out among numerous materials? This is inseparable from its unique physical properties, chemical stability, cost advantage and wide applicability.

Physical Properties Advantages of Carbon as Electrodes

Elektrische Leitfähigkeit

Graphite is a kind of allotropes of carbon, which has a typical layered structure. The carbon atoms in each layer are hybridified in sp²to form a hexagonal plane. And the electrons within the layers can move freely, giving it excellent electrical conductivity (up to 10⁴ S/m). This characteristic makes carbon an efficient medium for electron transmission in the electrode. When carbon is used as a battery electrode, it can quickly conduct electrons during the charging and discharging process, reducing internal resistance loss. In an electrolytic cell, high conductivity can reduce energy consumption and enhance reaction efficiency. Although the electrical conductivity of carbon is slightly inferior to that of copper and aluminum, it has more comprehensive advantages in scenarios such as corrosion resistance and lightweight.

Geringe Dichte

The density of carbon is much lower than that of metal electrode materials, usually between 1.5 and 2.3 g/cm³. This feature makes it indispensable in weight-sensitive fields such as power batteries and portable electronic devices. Using carbon materials as the negative electrode can significantly reduce the battery’s weight and increase its energy density. In addition, in high-end fields such as aerospace, the lightweight advantage of carbon electrodes can directly reduce equipment load and optimize overall performance.

Structural Diversity

The microstructure of carbon can take on various forms through process regulation:

Layered structure

The interlamellar distance of graphite is about 0.335 nm, which just allows lithium ions to intercalate. This makes it an ideal material for the negative electrode of lithium batteries. The diffusion rate of lithium ions can reach 10^-10 cm²/s, thus ensuring rapid charging and discharging.

Porous structure

After activation treatment, the specific surface area of activated carbon reaches more than 2000 m²/g. Because of the three-dimensional pore network, it can store charges in supercapacitors through the double-layer effect, and the power density can reach 10 kW/kg.

Nanostructure

The one-dimensional/two-dimensional forms of carbon nanotubes and graphene possess both high electrical conductivity and mechanical strength. So they are suitable for use as electrodes in flexible electronic devices and adaptable to complex working conditions like bending.

Chemical Properties Advantages of Carbon as Electrodes

Chemische Beständigkeit

At normal temperature and pressure, carbon hardly reacts with acid, base or salt solutions, so it can maintain structural stability in complex electrochemical environments. In the electrolytic cells of the chlor-alkali industry, carbon electrodes can resist the corrosion of strongly alkaline electrolytes. Even if the temperature rises, the stability of carbon remains prominent. For example, graphite, an indispensable material in high-temperature electrolysis, has a melting point that can reach 3652℃ in an inert atmosphere.

Korrosionsbeständigkeit

The corrosion resistance advantage of carbon is particularly significant. Carbon electrodes are hardly corroded in neutral or alkaline electrolytes and can maintain stable electrolytic efficiency. In addition, in highly corrosive scenarios like chemical wastewater treatment, the service life of carbon electrodes is much longer than that of metal materials. And then reducing equipment maintenance costs.

Catalytic Performance

Some carbon materials can exhibit catalytic activity after modification. For example, after doping with elements such as nitrogen and boron, you can use porous carbon as a catalyst for the oxygen reduction reaction (ORR). And you can usually apply them in fuel cells. The functional groups on the surface of activated carbon can promote the hydrogen evolution reaction (HER) in electrolyzed water. This dual function of “conductivity + catalysis” enables carbon electrodes to be both efficient and economical in the field of energy conversion. And it avoids the cost pressure of adding additional precious metal catalysts such as platinum.

Cost and Processability of Carbon Electrodes

Cost Advantage

The sources of carbon are extremely abundant: coal, petroleum coke, etc. can all be used as raw materials for carbon electrodes. And their prices are much lower than those of metals or rare materials. In addition, through methods such as high-temperature calcination, carbonization, and activation, they can be mass-produced. Because the preparation process of carbon materials is mature, costs are further reduced. This economic efficiency gives it an absolute advantage in large-scale industrial applications, such as lead-acid batteries and the chlor-alkali industry.

Verarbeitbarkeit

Carbon materials can be flexibly processed as required:

Powder molding

The carbon powder is mixed with the binder and rolled to produce the positive and negative Elektrode sheets of lithium batteries, with the thickness controllable within 50-150μm.

Fiber weaving

Three-dimensional materials such as carbon felt and carbon cloth have a porosity of 70%-80%. This increases the reaction area and is suitable for electrolytic electrodes of water.

Coating process

Carbon slurry is coated on metal substrates (such as titanium mesh) to prepare composite electrodes with both electrical conductivity and corrosion resistance. You can use them in the electroplating field.

Main Application Areas of Carbon Electrodes

Energy and Battery Fields

In the lithium batteries, you can use it as graphite anode. The layered structure of graphite allows for reversible intercalation of lithium ions, with a theoretical specific capacity of 372 mAh/g. To enhance performance, new materials such as hard carbon and soft carbon have been developed for fast charging and low-temperature scenarios.

Lead-acid batteries

Adding carbon materials to the positive electrode of lead-acid batteries as conductive agents can enhance their high-current discharge performance. With the cost advantage, they still hold an important position in fields such as car starting and energy storage power stations. And their energy density is approximately 50-70 Wh/kg, which are easy to maintain.

Supercapacitor

The porous structure of activated carbon makes its specific surface area exceed 2000 m²/g. Its power density reaches 10 kW/kg (10 times that of lithium batteries), but its energy density is low (5-10 Wh/kg). So it is suitable for scenarios with instantaneous high current such as fast charging of buses and starting of construction machinery.

Electrolysis Field

Wasser-Elektrolyse

In the alkaline electrolysis of water for hydrogen production, the corrosion rate of carbon felt electrodes in a 30% KOH solution is only 0.001 mm/ year. After loading the catalyst, the electrolysis efficiency exceeds 80%. With the development of the green hydrogen industry, the application of carbon-based electrodes continues to expand.

Aluminum Electrolysis Production

Aluminum electrolysis needs to be carried out in molten salt at 950-980℃, and Kohlenstoff-Anoden can work stably. Producing one ton of aluminum consumes 500-600 kilograms of carbon anodes. The global annual demand exceeds 30 million tons.

Chlor-Alkali Industry

Graphite anodes can resist chlorine corrosion and are cost-effective, with costs only 1/5 of those of titanium electrodes. So you can widely use them in traditional diaphragm electrolytic cells. Their catalytic activity can also reduce the voltage of the electrolytic cell and save electricity.

Electroplating Field

Unter Galvanik processes such as chromium plating, graphite anodes have strong corrosion resistance in strongly acidic electrolytes. And they can maintain a stable potential to ensure uniform coating. With good electrical conductivity and light weight, flexible Kohleelektroden have become the preferred choice for portable scenarios in brush plating.

Schlussfolgerung

The core advantages of using carbon as an electrode stem from the alignment of its physical and chemical properties with industrial demands. It is conductive and has diverse structures suitable for energy storage, is chemically stable and corrosion-resistant. And its cost and processing advantages promote large-scale application.