The Temperature-Programmed Desorption of H₂ from Cu/ZrO₂

Abstract

The desorption kinetics of hydrogen from a polycrystalline Cu/ZrO₂ catalyst was investigated under atmospheric pressure using temperature-programmed desorption (TPD) experiments in a microreactor set-up. Different heating rates were applied under equal conditions with a carefully reduced catalyst. The hydrogen TPD peaks were symmetric and centered slightly above 300 K indicating associative desorption of H₂ from metallic Cu. Using heating rate variation, the kinetic parameters $A_{des}$ and $E_{des}$ were determined to be 1.24 × 10⁹ s⁻¹ and 68 kJ mol⁻¹, respectively. As the modeling with constant values of $A_{des}$ and $E_{des}$ yielded signals which were too narrow, dependence of $E_{des}$ on coverage was introduced applying $E_{des} - K (\Theta _H)^n$. By application of the “full-analysis” method an optimal fit to the experimental data was found. Setting n = 1 resulted in the best fit and a value of 61 kJ mol⁻¹ − (6.25 kJ mol⁻¹ × $\Theta _H$) for $E_{des}$ was determined.

Graphical Abstract