How is surface area measured from nitrogen adsorption isotherm?
Answers
After studying this lecture, you will be able to do the following:
Use the Langmuir’s isotherm to calculate the surface area of adsorbent.
Use the BET (after Brunauer, Emmett and Teller) equation is used to give specific surface area from the
adsorption
data.
Use X-Ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Low Energy Electron
Diffraction(LEED) to characterize surface structures.
Use microscopic methods of characterization such as Scanning Electron Microscopy (SEM) and Scanning
Tunneling Microscopy (STM) to analyse surface structures of materials.
37.1 Introduction
Surface characteristics of a material refer to the properties associated with its surface. Typically measurements
of surface area, surface roughness, pore size, and reflectivity constitute surface characteristics. Information on
surface characteristics is very important for the possible applications of surfaces as semiconductors,
heterogeneous catalysts and also in biological research. Surface area is an attribute that is used by catalyst
manufacturers and users to monitor the activity and stability of a catalyst. There are different methods used to
measure different surface properties. Most methods are based on the isothermal adsorption of nitrogen. Many
advances in surface science have made the methods surface sensitive, i.e., they are sensitive to the outermost
atomic layers (depth of 2-3 atomic layers) of the bulk solids. These techniques could be classified into two
categories: Classical Methods and Instrumental methods