Tuning the d-Band center of High-Entropy oxides for selective aromatic oxidation and viscosity reduction in heavy oil

Despite abundant global reserves, the industrial utilization of heavy oil is severely limited by its extremely high viscosity, primarily caused by the aggregation of polycyclic aromatic hydrocarbons (PAHs). In this study, we propose a novel viscosity reduction strategy using spinel-structured high-entropy oxides (HEOs) as low-temperature catalysts requiring no additional oxidants, representing a significant departure from conventional thermal and oxidative methods. By tuning the d-band centers of multicomponent metal sites, the electronic structure of HEOs is optimized to selectively activate and moderately oxidize aromatic-rich asphaltenes. This catalytic process disrupts π–π stacking and introduces oxygen-containing functional groups, triggering a fundamentally new, irreversible viscosity reduction mechanism driven by molecular fragmentation and polarity modulation. Experimental validations, including rheological measurements, spectroscopic analysis, and model compound studies, reveal a substantial viscosity reduction of ∼ 75.05%. Mechanistically, the partial oxidation of asphaltenes promotes molecular disorder, releases trapped light components from the condensed matrix, and facilitates the penetration of surfactants, thereby lowering the oil–water interfacial tension. Overall, this work establishes HEOs as a next-generation catalytic platform and presents a new pathway for efficient and sustainable heavy oil mobility enhancement.