Gas adsorption

Gas adsorption can be broadly classified into two distinct types: physisorption and chemisorption, each driven by unique interaction mechanisms. These processes provide critical insights into material properties, enabling scientists and engineers to analyze surface area, porosity, and catalytic behavior.

Physisorption

Micromeritics gas adsorption analyzers are ideal for characterizing materials' surface area and pore structure. These instruments measure the amount of gas adsorbed under controlled pressure and temperature conditions, providing detailed insights into material porosity, pore size distribution, and specific surface area. Such data is essential for industries like pharmaceuticals, battery materials, and adsorbent development.

Chemisorption

For chemisorption studies, Micromeritics chemisorption analyzers  are engineered to evaluate the chemical reactivity and active surface sites of materials. These systems measure the strength and quantity of gas-surface interactions, helping to characterize catalysts, monitor surface reactions, and optimize catalyst performance in processes like hydrogenation, cracking, and reforming. This capability is invaluable in catalysis research and process development for energy and chemical industries.

Micromeritics' advanced technology ensures reproducible results and robust data, empowering researchers to fully understand and optimize material properties for their specific applications. 

The Brunauer-Emmett-Teller (BET) theory is a widely adopted method for measuring the specific surface area of materials. Typically, nitrogen gas (N₂) is used as the adsorbate due to its favorable interaction with most surfaces. By analyzing the amount of gas adsorbed at various pressures, the BET equation facilitates the calculation of the material's surface area.

The BET surface area of a material is calculated from the monolayer capacity which is the volume of the first single layer of gas molecules or atoms adsorbed on the surface.	The BET equation is linearized to conveniently calculate the monolayer capacity from the slope and y-intercept of the BET transform plot, which must achieve a sufficiently high correlation coefficient for a valid BET calculation, which is typically 0.999.

Gas adsorption enables characterization and structural analysis of material porosity. As gas pressure increases, pores within the material begin to fill. This process starts with smaller pores and progresses to larger ones until all are saturated. Overall, gas adsorption is applicable to pores ranging from ~0.35 nm to ~400 nm in diameter. Once details of the isotherm curve are accurately expressed as a series of pressure vs quantity adsorbed, a number of different methods (theories or models) can be applied to determine the pore size distribution.

Gas adsorption analysis plays a critical role across diverse industries by providing detailed insights into material properties, enabling the optimization of processes and products. Below are key applications and how they benefit various sectors:

Catalysis

The performance of catalysts is heavily influenced by their surface area, porosity, and active site availability. Gas adsorption techniques, such as chemisorption, allow for the precise characterization of catalyst surfaces, helping researchers evaluate properties like dispersion, metal-support interactions, and adsorption strength. This data is crucial for optimizing reaction efficiencies in processes like chemical synthesis, petroleum refining, and emissions control.

Pharmaceuticals

In drug development, the surface area and porosity of pharmaceutical powders directly impact solubility, dissolution rates, and bioavailability. Gas adsorption instruments are used to analyze these properties, ensuring that drug formulations are designed for optimal performance, stability, and delivery. This is particularly important for inhalable drugs and controlled-release formulations.

Battery material characterization

For energy storage technologies, such as lithium-ion and solid-state batteries, electrode materials with high surface areas and controlled porosity are essential for enhancing charge storage and ion transport. Gas adsorption analysis enables the precise evaluation of these material characteristics, contributing to the development of higher-capacity, longer-lasting, and more efficient batteries.

Environmental science

Gas adsorption is key to studying materials used for pollutant capture and removal, such as activated carbons and zeolites. By analyzing adsorption capacity, pore structure, and gas-solid interactions, researchers can optimize materials for capturing greenhouse gases, volatile organic compounds, and heavy metals. This technology supports cleaner air, water, and sustainable industrial practices.

Gas adsorption analysis is an indispensable tool for advancing material research and innovation across these industries, offering accurate, actionable data for product development and process optimization. 

What are other methods for characterizing a materials porosity?

Mercury Intrusion and Capillary Flow

What is the difference between Physisorption and Chemisorption

Physisorption and chemisorption are the primary types of gas adsorption. The differences are highlighted in the table below:

Physisorption (Physical Adsorption)	Chemisorption (Chemical Adsorption)
Non-selective	Selective
Weak Interactions (van der Waals)	Strong Interactions (chemical bonds)
Lower Energy	Higher Energy
Reversible	Irreversible & Reversible

At Malvern Panalytical, we provide advanced solutions for gas adsorption analysis, incorporating Micromeritics’ industry-leading instruments to deliver precise and reliable data for material characterization. These systems are designed to address diverse applications, from basic surface area measurements to in-depth porosity and catalytic analyses.

With these solutions, we empower researchers and industry professionals to gain deeper insights into material properties, enabling the development of innovative products and efficient processes. Malvern Panalytical’s expertise, combined with Micromeritics’ proven technology, ensures reliable results and outstanding support for your gas adsorption analysis needs.

• Application note: Characterizing advanced battery anodes with gas adsorption BET surface area and DFT surface energy
• Application note: Analysis of adsorbents for direct air capture of carbon dioxide using breakthrough analysis

Best practice for BET surface area

Best practice for BET surface area

Recorded webinar

Learn about BET surface area history, sample preparation and analysis parameter setup, and Micromeritics Software for BET measurements.