Surface Chemistry

Surface chemistry is a subfield of chemistry that studies the processes that occur at the interfaces of phases, such as solid and liquid, solid and gas and liquid and liquid. This subject is critical to our daily lives and a variety of sectors, ranging from materials and paints to medicine and biotechnology. Surfaces are critical in heterogeneous catalysis, colloidal formation and stability, and electrode reactions. Solids’ surfaces are intrinsically distinct from their bulk portions. At the surface, the bonding between the atoms is different than in the bulk. Hydrogen is generated on the surfaces of grains and dust particles in interstellar space. Mosquitoes and other small insects can walk on the surface of water but will drown if soaps are applied in the surrounding area. The spherical shape of water droplets and mercury droplets fascinates us. Additionally, we admire the non-sticky wings of butterflies and the leaves of plants. We are particularly drawn to the blue colour of the sky and the crimson colour of the sunset. Only the surface of matter is significant in all of the preceding. Numerous creams, lotions, and other skin care products are composed of complicated emulsions. Food manufacturers are interested in making products that are nutritious, tasty, and long-lasting. All of these are based on colloidal and surface chemistry principles.

Surface Chemistry

• Surface Chemistry is the study of chemical reactions that occur at interfaces such as solid-liquid, solid-gas, solid-vacuum, and liquid-gas.
• Because the gases are completely miscible, there is no interface between them.
• To conduct reliable Surface Chemistry investigations, it is critical to have a truly clean surface
• It is now possible to conduct experiments in extremely high vacuums on the scale of 10-8 to 10-9 Pascal. Ensure that the metals’ surfaces are ultra-clean.
• Solid materials with such clean surfaces must be stored in a vacuum; otherwise, the molecules of the primary components of air, such as dioxygen and dinitrogen, will cover them.
• Surface chemistry properties refer to the characteristics or traits of an object’s or molecule’s exterior boundaries.

Important topics in surface chemistry include adsorption, catalysis, colloids and emulsion.

Adsorption

• Surface Chemistry’s adsorption notion is based on the fact that the surface of a solid has a natural tendency to attract and retain molecules from the phase with which it comes into contact.
• These molecules remain at the surface and do not penetrate the bulk material.
• Adsorption is the process through which molecular species accumulate on the surface of a solid or liquid rather than in the mass.

Difference between Adsorption and Absorption in Surface Chemistry

Types of Adsorptions in Surface Chemistry

In Surface Chemistry, there are primarily two forms of adsorption: physisorption and chemisorption.

Physical adsorption or physisorption happens when gas accumulates on the surface of a material due to weak van der Waals forces.

Chemisorption refers to the adsorption of gas molecules or atoms on a solid surface via chemical bonds. Because it requires a large activation energy, it is frequently referred to as activated adsorption.

Application of Adsorption in Surface Chemistry

• To create a very high vacuum, the last traces of air can be absorbed by charcoal from a vessel evacuated with a vacuum pump.
• Gas masks: A gas mask (a device composed of activated charcoal or a combination of adsorbents) is typically used in coal mines to aid in the adsorption of hazardous gases.
• Humidity control: Silica and aluminium gels are used as adsorbents to absorb moisture and regulate humidity.
• Separation of inert gases: Due to the difference in the degree of adsorption of gases by charcoal, it is possible to separate a mixture of noble gases using adsorption on coconut charcoal at various temperatures.
• In illness treatment, a variety of medicines are employed to kill microorganisms via adsorption.
• Chromatographic analysis: Chromatographic analysis, which is based on the adsorption phenomenon, is used in a variety of analytical and industrial applications.

Catalysis in Surface Chemistry

• Catalysts are substances that increase the rate of a chemical reaction while remaining chemically and quantitatively unaltered after the reaction, and the phenomenon is referred to as catalysis in Surface Chemistry.
• Promoters are compounds that increase a catalyst’s activity, whereas poisons diminish a catalyst’s activity.
• For instance, in Haber’s ammonia manufacturing method, molybdenum works as a promoter for the iron utilised as a catalyst.

Colloidal Solution in Surface Chemistry

• Colloids are mixes in which insoluble particles of one substance are suspended in another component at a tiny scale.
• A colloid’s suspended particles can range in size from 1 to 1000 nanometers.
• To qualify as a colloid, a mixture’s suspended particles must not settle (in the manner that the particles of suspensions settle at the bottom of the container if left undisturbed).
• Colloidal solutions are known to show the Tyndall effect, a phenomenon in which light beams incident on colloids are scattered as a result of the light’s interactions with the colloidal particles.

Conclusion

Surface Chemistry is the study of chemical reactions that occur at the interface between two surfaces, which can be solid-liquid, solid-gas, solid-vacuum, or liquid-gas. Surface engineering is a term that refers to some applications of surface chemistry. Numerous phenomena occur on the surface of substances, including the following:

• Adsorption
• Catalysis by Heterogeneity
• Corrosion
• Crystallization