Unraveling Alkali Ion Electron Donation for Enhancing Heterogeneous Catalytic Oxidation

Alkali ions, widely employed as promoters, play crucial roles in heterogeneous catalysis. However, their electron donation mechanism remains poorly understood because alkali ions do not have transferable electrons as metallic alkalis do. Here, a new mechanistic pathway is identified for potassium (K) ions to act as electron donors by constructing single chains of K ions confined within hexagonal WO₃ tunnels with theoretical limit-breakthrough K concentrations. The as-produced high-electron-density K^δ+ (0<δ<1) ions not only facilitate the formation of oxygen vacancies that behave classical electronic effect but, more importantly, also directly donate electrons to [WO₆] motif antibonding orbitals, thereby triggering the lattice oxygen activation. As a proof of concept, the resultant catalyst containing K^δ+ ions predominantly promotes soot oxidation with O₂, a challenging solid-solid-gas reaction in automotive catalysis, achieving a reaction rate 3.1-fold greater than the conventional K⁺-ion confined counterpart. The electron donation effect of metalloid K^δ+ ions would be heuristic for enhancing other important heterogeneous catalytic reactions.