Modified Carbon-Based Electrodes: Properties, Fabrication, and Applications

1. Conductive Forms of Carbon

Conductive carbon is a material that has attracted intense interest, especially during the last two decades [1]. . Its properties, combined with its environmental friendliness, contribute to the increasing industrial production of composite materials made from conductive forms of carbon, which find applications in fields with special requirements and high specifications, such as aerospace engineering, the automotive industry, and energy production industries. Research in the field of conductive carbon forms aims at improving their properties and expanding their applications into other areas of science and industry.

The ability of carbon to conduct electric current is one of its most important properties, making it a valuable material in the electrochemical industry.[2]. Carbon is already widely used in electrosynthesis, fuel cells, and even organic fuels, which constitute an important field in chemistry with both theoretical and practical interest. The electrical conductivity of carbon is due to its graphitic structure. This consists of a parallel arrangeme nt of layers of carbon atoms. Within each layer, carbon atoms are connected through covalent bonds and form hexagonal rings extending into a two-dimensional lattice. The lattices are connected to each other through Van der Waals forces.

The internal graphitic planes exhibit hydrophobic character, low polarity, non-ionic behavior, and high π-electron density. These properties facilitate the chemisorption of various organic substances between these planes. [3]. At the external graphitic planes, especially at the edges, functional groups such as carboxyl, hydroxyl, amino, and others can be formed through a series of processes that improve the mechanical and physicochemical properties of graphitic materials, generally referred to as surface modification.

Depending on the raw material used for the preparation of graphitic materials and their processing method, the following types are produced:

• Carbon fibers
• b) Glassy carbon
• c) Pyrolytic graphite
• d) Graphite sheets

Although the carbon bonds in these materials are approximately the same, their properties differ significantly because of the size and arrangement of graphite crystals. The surface structure of carbon (presence of hydroxyl, ketonic, carboxylic, and other groups) affects its reactivity, the kinetics of charge-transfer reactions, and makes it especially suitable for adsorption.

1.1. Graphitized Carbon Fibers (Carbon Fibers)

Carbon fibers (CF) appeared in the beginning of the 20th century and were mainly used as filaments in electric lamps.[4]. The first fibers were produced by carbonizing bamboo. In the 1950s, highly elastic fibers were first manufactured using rayon as the raw material. From the 1960s onward, the carbon fiber industry developed rapidly, aiming at the production of fibers with improved mechanical and physicochemical properties. Improvements in production methods, combined with the different raw materials used today, enabled the production of many types of carbon fibers with specific mechanical and physicochemical properties depending on their intended applications.

The diameter of carbon fibers ranges from 0.1 to 100 μm, with most fibers falling within the 5–25 μm range. They have negligible weight, and the hardness of their structure exceeds even that of steel. Their major advantage is their small size, which makes them suitable for the construction of microelectrodes and for in vivo analyses.

Graphitized carbon fibers are obtained through carbonization of various organic compounds followed by graphitization of the resulting products.[5]. Although they are relatively new materials, they already have many applications and are considered promising tools for future technologies. Commercially available carbon fibers can be classified into four main categories according to their raw material:

• Polyacrylonitrile fibers (PAN fibers)
• b) Pitch fibers
• c) Rayon fibers
• d) Vapor-grown fibers

For the production of carbon fibers with high elastic modulus and high electrical conductivity, the graphite planes formed during graphitization of rayon or polyacrylonitrile must be oriented parallel to the axis of the plastic fiber. This orientation is nearly perfect in graphite fibers derived from polyacrylonitrile.

1.1.1. Polyacrylonitrile Graphitized Fibers (PAN)

Fibers obtained from graphitization of polyacrylonitrile constitute an especially valuable raw material for electrode fabrication. Their preparation is relatively simple, and fibers with high elastic modulus and high conductivity can be produced.

During production, PAN fibers undergo a thermal treatment stage at temperatures not exceeding 400°C. This stage ensures their stabilization so that they will not degrade during subsequent processing steps. This is followed by the carbonization stage, where fibers are heated in an oxygen-free environment and impurities are removed. In the next stage, graphitization and elongation of the fibers by 50–100% occur at temperatures between 1100°C and 3000°C. Fiber elongation ensures the proper orientation of crystals. The final stage involves surface treatment and sizing so that the fibers become more compatible with the materials with which they will be combined.

Graphitic carbon fibers possess a large active electrode surface area and excellent mechanical stability. Electrodes made from PAN carbon fibers exhibit very high resistance even in highly acidic solutions.[6] Their durability remains even after surface modification. Furthermore, these microelectrodes are suitable for analyses of small-volume samples, function effectively in low-conductivity media, and allow satisfactory mass transfer without forced convection (such as stirring or electrode rotation).

1.2. Glassy Carbon

Glassy carbon (GC) exhibits very good mechanical and electrical properties. Its surface is smooth, highly dense, and consists of very small pores.[7] Its electrode reactivity depends on the nature and history of the carbon surface. The usual pretreatment involves activation through polishing on special cloths impregnated with alumina (Al₂O₃) suspension; therefore, no extensive pretreatment is required other than the creation of active repetitive groups.

Glassy carbon electrodes are frequently used in chemical sensors. Glassy carbon is produced by heating polyacrylonitrile or phenol/formaldehyde polymers at 1000–3000°C under pressure. It is a material that does not graphitize even at 3000°C. Due to thermal treatment during preparation, it develops high porosity (95–97% air), and its surface area is approximately 65 cm²/cm³.

Glassy carbon has excellent mechanical properties and, unlike graphite, is hard and impermeable to water and organic solvents. Background current, potential window, and the kinetics of electrode reactions vary depending on cleaning and pretreatment. The background current is generally slightly higher than that of polycrystalline graphite.

Depending on the application, electrodes may undergo laser irradiation, thermal treatment, or electrochemical pretreatment, resulting in increased kinetics, selectivity, and sensitivity of electrode reactions.

1.3. Characteristic Properties of Graphitized Carbon Fibers

1.3.1. Mechanical Properties

Graphitic fibers exhibit exceptional physical and mechanical properties. Due to their “textile” origin, they allow the construction of electrodes consisting of bundles containing a large number of fibers, thus providing large surface area and mechanical stability. Carbon fiber electrodes are not easily mechanically stressed, whereas other forms of graphite, such as pyrolytic graphite and graphite sheets, readily undergo degradation.[8]

The final quality of carbon fibers depends on both the raw material and the production parameters. During heating at the final stage of graphitization (for temperatures above:

T>2500∘CT > 2500^{\circ}CT>2500∘C

their weight decreases significantly while the degree of crystal orientation parallel to the fiber axis increases. This leads to fibers with much better mechanical properties. It has been found that Young’s modulus depends on the final treatment temperature. This stage plays an important role both in quality and in production cost.

1.3.2. Electrical and Thermal Properties

As already mentioned, carbon fibers produced by high-temperature carbonization consist of graphitic hexagonal crystals highly oriented along the longitudinal axis of the fibers. Consequently, carbon fibers exhibit high electrical conductivity along this axis and are widely used in the production of conductive materials.

Carbon fibers also possess important thermal properties. They exhibit high heat capacity and a very low coefficient of linear thermal expansion. These properties make them excellent materials for applications requiring high heat dissipation.

The use of electrodes made from carbon fiber bundles in electrolytic solutions is relatively simple compared to other carbon electrode materials.[9] Their surfaces do not require regeneration, and they provide reliable cyclic voltammograms over a wide potential range.

Graphitic fibers can also be used as modified electrodes because it is possible to create controlled functional groups onto which atoms or molecules bearing additional functional groups may be attached. Through special electrochemical oxidation and simple chemisorption of suitable metal oxides or reversible redox couples, the fibers can also become excellent high-capacitance systems.

The text discusses the importance of conductive carbon materials in electrochemical applications, particularly for improving the electrocatalytic properties of electrodes. Carbon-based electrodes are environmentally friendly, highly conductive, and widely used in electrosynthesis, fuel cells, sensors, and electrochemical analyses.

The electrical conductivity of carbon originates from its graphitic structure, which consists of layered hexagonal carbon lattices connected by Van der Waals forces. Surface functional groups such as hydroxyl, carboxyl, and amino groups influence the material’s reactivity and adsorption properties.

Four main forms of graphitic carbon are described:

• pyrolytic graphite,
• glassy carbon,
• carbon fibers,
• graphite sheets.

Special emphasis is placed on graphitized carbon fibers and glassy carbon because of their electrochemical applications.

Carbon fibers possess:

• high electrical conductivity,
• excellent mechanical strength,
• low weight,
• small diameter suitable for microelectrodes and in vivo analysis.

Among them, polyacrylonitrile-based (PAN) carbon fibers are particularly important. Their production involves stabilization, carbonization, graphitization, and surface treatment at very high temperatures. These processes improve crystal orientation, conductivity, elasticity, and chemical resistance. PAN fiber electrodes exhibit large active surface area, stability in acidic media, and effective mass transfer.

Glassy carbon is another important electrode material characterized by:

• smooth and dense surface,
• high mechanical strength,
• chemical inertness,
• impermeability to water and organic solvents.

Its electrochemical behavior depends strongly on surface pretreatment and activation methods.

Finally, the text highlights the mechanical, electrical, and thermal properties of graphitized carbon fibers. [10]. Dordrecht: Springer Netherlands. Their high conductivity, thermal stability, and mechanical durability make them ideal materials for advanced electrochemical systems and modified electrodes with enhanced catalytic and capacitive properties.

In addition, graphitized carbon fibers can be chemically modified in order to enhance their electrochemical performance. Through electrochemical oxidation or adsorption of metal oxides and redox-active compounds, their surface can acquire specific functional groups that improve sensitivity, selectivity, and catalytic activity. This makes them highly suitable for applications in sensors, energy storage systems, fuel cells, and analytical chemistry.

Another important advantage of carbon-based electrodes is their stability over a wide potential range and their ability to provide reliable cyclic voltammetric responses without frequent surface regeneration. Compared to other graphite materials, carbon fiber electrodes show greater resistance to mechanical degradation and maintain their performance even under harsh chemical conditions.

The thermal properties of carbon fibers are also significant. Their high heat capacity and low thermal expansion coefficient allow efficient heat dissipation, which is essential in high-performance industrial and electrochemical applications.

Overall, graphitized carbon fibers and glassy carbon are considered highly promising materials for modern electrochemical technologies [11] because they combine:

• high electrical conductivity,
• excellent mechanical stability,
• chemical resistance,
• tunable surface properties,
• and strong electrocatalytic behavior.

These characteristics make them ideal candidates for advanced electrode fabrication and future developments in electrochemistry, energy conversion, and sensing technologies.

The continuous development of carbon-based electrode materials has led to significant advances in both fundamental research and industrial applications. Scientists are increasingly focusing on the design of modified carbon electrodes with nanostructured surfaces and controlled functionalization in order to achieve faster electron-transfer kinetics and improved catalytic efficiency.

One of the major advantages of carbon electrodes is their versatility. By introducing different surface groups or depositing metallic and organic layers onto the carbon surface, the electrochemical properties of the electrodes can be tailored for specific reactions. Such modifications can enhance:

• electron-transfer rates,
• adsorption of target molecules,
• sensitivity toward analytes,
• and long-term operational stability.

In electroanalysis, carbon electrodes are widely used for the detection of biologically and environmentally important compounds because they provide:

• low background currents,
• broad potential windows,
• high sensitivity,
• and good reproducibility.

Microelectrodes made from carbon fibers are especially useful in biological systems and in vivo measurements due to their very small dimensions. Their size minimizes damage to biological tissues while allowing rapid mass transport and accurate measurements in small sample volumes.

In energy-related applications, graphitized carbon materials are employed in:

• supercapacitors,
• lithium-ion batteries,
• fuel cells,
• and electrochemical energy conversion systems.

Their large surface area and high conductivity contribute to efficient charge storage and transfer. Furthermore, their chemical and thermal stability ensures reliable operation under demanding conditions.

Research in this field continues to expand toward the development of hybrid materials that combine carbon structures with nanoparticles, conductive polymers, or metal oxides.[12] These hybrid systems often exhibit synergistic effects, resulting in improved electrocatalytic activity and enhanced electrochemical performance.

Therefore, conductive carbon materials, particularly graphitized carbon fibers and glassy carbon, remain at the forefront of modern electrochemical science and technology, offering broad possibilities for future innovations in sensing, catalysis, environmental monitoring, and sustainable energy systems.

2. Modification of Graphitized Carbon Fibers

Until recently, electrochemical applications mainly used pure electrodes made of various metals or graphite. However, it has recently been observed that the addition or presence of various atoms or molecules on electrode surfaces results in changes in the mechanism and kinetics of many electrode reactions. Electrode modification can be used to direct certain electrochemical reactions toward a desired pathway or desired product.[13]

The main goal of modifying graphitized fibers is the creation of suitable functional groups mainly on their surface but also within their interior. These functional groups may originate either from the graphite material itself or from molecules attached to it. By controlling the type and quantity of functional groups, the hydrophilic or hydrophobic character of the modified graphitic fibers can be altered. These groups can bind ions, molecules, or polymer macromolecular groups. The ability to control the type and amount of functional groups allows graphitic fibers to be used in a wide range of electrochemical applications and studies.

The characteristic of modified electrodes is generally a thin film of a specific chemical compound bonded or deposited on an electrode surface, giving it desired chemical, electrochemical, electrical, and other properties. Modified electrodes are usually manufactured by modifying a conductive substrate to create an electrode whose properties differ from those of the substrate.

The processes for modifying graphitic fibers can be divided into two general stages:

In the first stage, oxidation processes (chemical, photochemical, electrochemical, etc.) are usually carried out, resulting in the formation of oxygen-containing groups from the graphite material itself, namely carbon.[14] These groups have the advantage of being strongly bonded to the rest of the graphitic material.

In the second stage, processes are included that generally achieve the attachment of ions or molecules, as well as those leading to the final product, which is usually electrode material.[15] The attachment of functional groups at this stage can be achieved:

• By chemical reaction of the surface groups of graphitic materials with molecules of various substances.
• By deposition of metal layers after ion exchange of their ions with the hydrogen cations of the groups.
• By simple chemical adsorption of monomeric or polymeric substances.
• Indirectly, by trapping the electroactive substance within a polymer.

Chemisorption is based on the adsorption of the electroactive substance onto the electrode surface. The molecules are held on the surface by Van der Waals electrostatic forces, while in the case of aromatic compounds, immobilization is due to interactions between the π-electrons of the aromatic ring and the electrons of the electrode surface.

A disadvantage of this method is the difficulty in achieving completely irreversible adsorption, resulting in desorption of the electroactive substance over time in many cases.

2.1. Modification by Oxidation

Carbon fibers can be modified through oxidation using various methods to form functional groups (e.g., –COOH and –OH groups) on their surface. Through this process, the core of the fibers remains unaffected, meaning that the fibers retain their original mechanical stability and electrical conductivity. Noble metals (Ag, Au, Pt, Pd) can be introduced into the carbon matrix through an ion-exchange process followed by chemical or electrochemical reduction.

In general, graphitic carbon oxidizes slowly even during simple exposure to air. However, in order to create a large number of specific oxygen-containing active groups, the graphitic material is subjected to various oxidation treatments.

The main methods for producing surface groups on carbon are:

a)

Thermal or photochemical oxidation in air in the presence of water vapor.

b)

Chemical oxidation by immersion of fibers in oxidizing solutions.

c)

Oxidation using oxygen plasma.

d)

Electrochemical (anodic) oxidation in aqueous acid solutions.

It has been found that depending on the method and conditions used, oxidation may remain superficial, forming surface oxides, or extend into the interior, forming bulk oxides.

Surface oxides consist of oxygen-containing groups, mainly carboxylic, phenolic, and carbonyl groups located at the edges of graphitic planes. Internal oxides consist of compounds of carbon, hydrogen, and oxygen where oxygen is strongly bonded between successive hexagonal graphitic planes.

Surface oxides exhibit adsorption and ion-exchange properties and, combined with high electrical conductivity, mechanical stability, and durability, form an excellent substrate for the creation of modified electrodes with a large electrochemically active surface.

Fibers subjected to electrochemical oxidation acquire a large number of active ion-exchange groups while maintaining high conductivity and mechanical stability because the graphitic core remains unchanged.[16]

The conditions of electrochemical oxidation directly affect the number of surface-active ion-exchange groups, which in turn determines the suitability of the oxidized graphitic substrate as a catalytic support. It has been demonstrated that a significant increase in the number of surface ion-exchange groups can be achieved through alternating electrochemical oxidation and reduction using potentiostatic pulses in aqueous Na₂SO₄ solutions. With this method, active oxygen-containing groups are created that extend into the internal planes of the graphitic fibers. Thus, although a thick layer of surface oxides is formed, the core of the graphitic fibers is not altered, and both mechanical stability and conductivity are satisfactorily maintained.

2.2. Modification by Attachment of Molecules or Groups to the Electrode Substrate

The modification of graphitized fibers can also be achieved using the technique of attaching molecules or groups to the graphitic material. For many years, mixed electrode systems have been widely used, meaning electrodes on whose surfaces various atoms or molecules are deposited.

In 1975, Murray and his collaborators first used the term “chemically modified electrodes” to describe electrodes on whose surfaces molecules of foreign substances are attached in such a way that the electrode material exhibits the properties of the attached substance.[17] In this way, new electrode systems with selected chemical and electrochemical properties can be obtained, which can be used in specialized electrode reactions.

Modified electrodes have many applications, mainly in electrocatalysis, but also in the construction of photoelectrodes, selective electrosynthesis, and analytical determinations. Recently, there have also been reports of their application in the development of supercapacitors, which are of great interest due to their many important applications, especially in electric vehicles.

Their applications in supercapacitors are based on the fact that they provide a large active surface area, resulting in the double layer formed between the electrode and the electrolyte solution having very high capacitance compared to conventional capacitors made from different materials. Furthermore, the presence of molecules, mainly metal oxides or reversible redox systems attached to the fiber surface, act as very fast intermediate electron carriers, increasing charge density and system capacitance even further.

2.3. Modification with a Thin Bismuth Film

2.3.1. Bismuth

Bismuth is an environmentally friendly metal (often called “the green metal”), with low toxicity and broad pharmaceutical use.[18] It exhibits high conductivity as well as high electrical resistance. It is not a highly reactive element and is not attacked by dilute acids, although it is attacked by concentrated sulfuric acid and nitric acid. It is stable in oxygen and water, where it forms insoluble salts.

2.3.2. Substrates

Bismuth can be used as a coating or film on various forms of carbon, such as:

• Carbon fibers
• Carbon paste
• Glassy carbon
• Wax-impregnated graphite
• Pencil-lead graphite
• Screen-printed carbon ink electrodes (SPCE)

Applications have also been made using carbon-fiber microelectrodes or gold and platinum wire microelectrodes, which can be used for analyses in small sample volumes and in low-conductivity solutions because they increase small capacitive currents and allow efficient mass transfer in stripping techniques.

Carbon fibers are easily manufactured, low-cost, and produce low background current. Glassy carbon electrodes also exhibit very low background current but are somewhat expensive. Carbon paste electrodes are easy to construct and activate and are also inexpensive. The same applies to pencil-lead electrodes, which are additionally widely available on the market.

2.3.3. Fabrication of Bismuth Electrodes

The most common technique for forming a Bi layer is electrodeposition onto various forms of carbon and metals (Cu, Au, Pt) [19]

There are two techniques for electrodepositing Bi onto a conductive surface:

1. Ex-situ Electrodeposition

This technique involves electrodeposition of bismuth ions before transferring the electrode into the sample solution for analysis.

The coating conditions affect the quality of the formed Bi film. For example:

• Acidic media are generally recommended because Bi(III) hydrolyzes easily at higher pH values.
• Bi(III) concentrations range from 5–200 mg/L.
• Deposition potentials range between –0.5 and –1.2 V.
• Deposition times range from 1–8 minutes under forced convection conditions (rotating electrode or mechanical stirring).

2. In-situ Electrodeposition

In this technique, bismuth ions (200–1000 μg/L) are added directly to the sample solution, and preconcentration occurs simultaneously with the analytes by applying a potential to the electrode surface during analysis.

In this case, both the potential and the preconcentration time are influenced by the analytes being determined.

The limitation of this method is that the concentration of Bi(III) must be at least ten orders of magnitude greater than the expected analyte concentration to avoid saturation effects.

Its main advantage is that it simplifies and shortens the experimental procedure. However, its use is limited mainly to anodic stripping determinations, where negative electrode potentials are applied for electrolytic preconcentration of metal ions.

Additionally, it is applicable only within specific pH ranges, mainly weakly acidic solutions, because Bi(III) ions hydrolyze easily in neutral and alkaline media according to the reaction:

Bi³⁺+3H2O→Bi(OH)₃+3H⁺ (2.1)

In strongly alkaline media (e.g., NaOH, NH₃), Bi forms stable hydroxyl complexes instead of hydrolyzing:

Bi³⁺+OH^-→Bi(OH)²⁺ (2.2)

These complexes dissolve in aqueous media and are reduced on the electrode surface. Under similar alkaline conditions, mercury-film electrodes are unsuitable because Hg ions undergo hydrolysis.

Comparatively, pre-deposition has the advantage of being independent of parameters such as pH or preconcentration conditions since it is performed separately from the determination step. However, this also makes it more complex and time-consuming.

Other types of Bi electrodes can be fabricated by modifying their bulk mass with a precursor bismuth compound such as Bi₂O₃. At a potential of –1.0 V, Bi₂O₃ is reduced to metallic Bi according to the reaction:

Bi₂O₃(s)+3H2O+6e⁻→2Bi(s)+6OH⁻ (2.3)

This method is especially suitable for carbon paste electrodes because Bi₂O₃ can easily be mixed with the carbon paste. The advantages of these modified electrodes include easy preparation and simplified experimental procedures without using bismuth salts. Their disadvantages involve problematic applications in anodic stripping voltammetry for heavy metal determination, as they do not exhibit good linearity or repeatability.

Finally, Bi electrodes can be coated with various polymers such as Nafion, which prevent the adsorption of macromolecules and can increase the selectivity and sensitivity of the determination.

• On glassy carbon, the thin bismuth layer is characterized by a three-dimensional porous structure.
• In the case of carbon-fiber microelectrodes, the structure is much more uniform.

• The preconcentration potential
• The composition of the preconcentration solution

2.4. Applications of Bismuth Electrodes

Bismuth electrodes are widely applied in trace analysis using electrochemical stripping techniques, in which the analyte is preconcentrated before measurement either electrolytically or by adsorption.

Various voltammetric scanning techniques have been applied. Although amalgam formation contributes to the stripping behavior of mercury electrodes, the impressive and unique stripping behavior of bismuth electrodes is attributed to the formation of multicomponent compounds.

It is known that bismuth forms “fused” binary or multicomponent compounds with a large number of heavy metals [23,24,25,26].

Conclusions

The development of graphitized carbon fibers and bismuth-modified carbon electrodes has significantly expanded the capabilities of modern electrochemical and electroanalytical systems. Their combination of excellent electrical conductivity, mechanical stability, chemical resistance, and environmentally friendly composition makes them highly attractive alternatives to conventional electrode materials, particularly mercury-based electrodes.

Graphitized carbon fibers provide an outstanding substrate for electrode fabrication because of their large electrochemically active surface area, high conductivity, low background currents, and excellent durability. Their small dimensions also enable the construction of microelectrodes suitable for in vivo analysis, trace detection, and measurements in small sample volumes. Furthermore, their surface chemistry can be readily modified through oxidation or chemical functionalization, allowing precise control of electrocatalytic properties and analyte selectivity.

Surface modification plays a central role in enhancing electrode performance. Electrochemical oxidation introduces oxygen-containing functional groups without compromising the conductive graphitic core, while the attachment of metal oxides, polymers, or redox-active compounds further improves electron-transfer kinetics, adsorption characteristics, sensitivity, and long-term stability. These modifications enable the fabrication of tailored electrode systems for a broad range of electrochemical applications.

Among surface modifiers, bismuth has emerged as one of the most promising materials because of its low toxicity, favorable electrochemical behavior, and compatibility with numerous carbon substrates. Thin bismuth films can be deposited either ex situ or in situ, providing sensitive, reproducible, and environmentally benign electrodes for stripping voltammetry. The morphology and thickness of the deposited film strongly influence analytical performance, and optimized coatings can achieve detection capabilities comparable to or even exceeding those of traditional mercury-film electrodes.

The versatility of bismuth-modified electrodes has led to numerous applications in the determination of trace heavy metals, environmental monitoring, biological analysis, and electrochemical sensing. Their high sensitivity, wide potential window, and low background current make them particularly suitable for anodic and adsorptive stripping voltammetry, while ongoing developments involving nanostructured materials, conductive polymers, and hybrid composites continue to improve their analytical performance.

Overall, graphitized carbon fibers and bismuth-modified electrodes represent an important class of advanced electrochemical materials that combine sustainability with high analytical performance. Continued research into novel surface functionalization strategies, nanostructured coatings, and hybrid electrode architectures is expected to further expand their applications in analytical chemistry, environmental monitoring, biosensing, energy storage, and electrocatalysis, reinforcing their role as key materials for the next generation of electrochemical technologies.