H₂ activation on catalysts critically depends on adsorbed H species. This review classifies H formation via homolytic/heterolytic dissociation at metal sites, focusing on Pt-based systems. We analyze Pt─H adducts using IR, INS, and XAS spectroscopy, complemented by theoretical studies of bonding and dynamics. By evaluating characterization methods and future directions, we bridge experiment-theory gaps to advance hydrogen-involved catalysis.

Abstract

H₂ activation on heterogeneous catalysts is a fundamental step in numerous chemical processes, with the nature of adsorbed hydrogen (H) species playing a critical role in catalytic performance. In this review, we systematically categorize the formation of different H species based on the coordination environment of active metal sites, distinguishing between homolytic and heterolytic H₂ dissociation pathways. Focusing on Pt-based heterogeneous catalysts, we provide atomic-scale insights into adsorbed H species and Pt metal. The experimental detection of Pt─H adducts is then critically evaluated via three key spectroscopic techniques: infrared (IR) spectroscopy, inelastic neutron scattering (INS) spectroscopy, and X-ray absorption spectroscopy (XAS), highlighting recent advancements in spectral interpretation. Complementary theoretical studies that can provide binding details of Pt─H bonds are also discussed to elucidate Pt─H adsorption configurations, binding energies, dynamic properties, and coverage-dependent behavior. Finally, we summarize the strengths and limitations of each characterization method and provide perspectives on future research directions for understanding adsorbed H species in catalysis. This review aims to bridge the gap between experimental observations and theoretical modeling, offering a comprehensive foundation for designing more efficient catalysts in hydrogen-involved reactions.