The BET method involves exposing a known amount of material to a gas (usually nitrogen) at liquid nitrogen temperature. As the gas adsorbs onto the material's surface, the pressure is monitored. The amount of gas adsorbed is then used to create a BET plot, which helps calculate the surface area. The BET equation is given by:
where V is the volume of gas adsorbed, P0 is the saturation pressure, P is the equilibrium pressure, C is the BET constant, and Vm is the volume of gas adsorbed at monolayer coverage.
