temperatureprogrammed

Temperature-programmed refers to experimental approaches in which the temperature of a sample is controlled according to a predefined time-dependent profile during measurement. This method contrasts with isothermal techniques, where the temperature is held constant. Typical temperature programs involve linear or stepwise ramps, with heating or cooling rates chosen to suit the material and technique, and to reveal thermally activated processes. Measurements performed during the program can include mass spectrometry, thermogravimetric analysis, infrared spectroscopy, calorimetry, or surface probes to monitor desorption, adsorption, reaction products, or structural changes as a function of temperature.

Common variants carry the descriptor temperature-programmed with specific target processes, such as temperature-programmed desorption (TPD), reduction (TPR), or oxidation (TPO). In TPD, adsorbed species are gradually removed from a surface and detected, yielding information on binding energies and surface coverage. In TPR, reducible oxides are heated in a flow of hydrogen or another reactant to monitor reduction steps and to infer active sites and reaction kinetics. Temperature-programmed measurements are widely used to study catalysts, adsorbents, and materials with temperature-dependent properties.

Data interpretation often focuses on onset and peak temperatures, as well as peak areas, which can be related to activation energies or binding energies under certain analytical assumptions. The approach provides insights into kinetics, mechanisms, and thermal stability, complementing other characterization methods.

Limitations include potential temperature gradients within the sample, thermal lag, and dependence on the heating rate or atmosphere. Careful calibration and control are essential for reliable results.