Analogy in the Mechanism of Heterolytic H<sub>2</sub> Dissociation
Ping Jin, Nengchao Luo, Feng Wang
Abstract
Hydrogenation is an essential type of reaction and dominates reduction reactions in the chemical industry, such as ammonia synthesis, Fischer–Tropsch synthesis, and the reduction of unsaturated chemical bonds. Metal nanoparticle-based homolytic H 2 dissociation enables hydrogenation reactions while being less selective for polar functional groups. Heterolytic H 2 dissociation creates polar reductive species of H δ+ and H δ− pairs, enabling regioselective hydrogenation and moderating the hydrogenation extent. Classical heterolytic H 2 dissociation on metal oxides occurs at elevated temperatures. Recent advances in heterolytic H 2 dissociation are identified at solid-frustrated Lewis pairs and supported metal catalysts including defective oxides, supported metal nanoparticles, single atoms, and ligand-decorated metal nanoparticles. Although exhibited in different forms, heterolytic H 2 dissociation necessitates polar pairs and can be simplified as acid–base pairs to polarize the H 2 molecule. In this Perspective, with an initial review of classic homolytic and heterolytic H 2 dissociation for comparison, we elucidate the unified mechanism of different forms of heterolytic H 2 dissociation on heterogeneous catalysts, aiming to inspire findings on heterolytic H 2 dissociation that operates with activity comparable to that of homolytic H 2 dissociation on metal nanoparticles.