Probing Heterolytic H2 Dissociation on Heterogeneous Catalysts: A Brief Review of Experimental Strategies

Abstract

Hydrogen (H2) has become a more important alternative source in the current energy transition process. Beyond its role in clean energy production, it also serves as a key reactant in a wide range of industrial chemical transformations, such as hydrogenation and hydroprocessing. A fundamental step in many of these processes is the dissociation of hydrogen on catalyst surfaces. This short review provides an overview of the fundamental mechanisms involved in hydrogen dissociation over catalysts, with a specific emphasis on heterolytic pathways. Meanwhile, the influence of surface coordination environments on hydrogen activation is discussed, focusing on key factors—Lewis acid–base pairs, lattice oxygen and oxygen vacancies, and metal–support interfaces. With recognizing the significance of understanding the reaction mechanisms, we provide a critical review of experimental techniques, including spectroscopy, temperature-programmed methods, and kinetic analysis, that have been successfully applied or appear promising for probing active sites, reaction dynamics, chemisorbed intermediates, and elementary steps. Our goal is to highlight how these techniques contribute to a mechanistic understanding and to outline future directions, making this review a valuable resource for both new and experienced researchers.