Tunable Electronic Structure in Spinel-Type Mixed Metal Oxides for Selective Oxidation of Light Alkanes through Correlated Spectroscopic and Kinetic Analysis

Abstract

The selective oxidation of light alkanes represents a fundamental challenge in heterogeneous catalysis due to the inherent chemical inertness of C–H bonds and the propensity for complete combustion. Spinel-type mixed metal oxides have recently emerged as promising catalysts for controlling activity and selectivity in these transformations. In this study, we explore the tunability of electronic structures in Co-, Mn-, Cu-, and Ni-containing spinel oxides and their impact on the partial oxidation of methane, ethane, and propane. A comprehensive correlation between in situ spectroscopic analysis (XPS, DRIFTS, and UV–Vis) and kinetic measurements is established to elucidate the role of surface oxygen vacancies, cation distribution, and metal–metal electronic interactions in governing catalytic performance. Our results indicate that A-site cation substitution (Co, Cu, Ni) in AMn2O4 spinels strongly modulates the oxidation state distribution of B-site metals, directly influencing lattice oxygen mobility and enhancing selective conversion pathways. Spectroscopic evidence demonstrates that charge transfer at oxide–oxide interfaces, especially in Co3O4–CeO2 and Cu-Mn spinel systems, significantly accelerates C–H activation via a Mars–van Krevelen-type mechanism. Kinetic analysis reveals first-order dependence on alkane concentration, with minor inhibition by H2O and variable sensitivity to O2 partial pressure, consistent with a lattice oxygen-mediated reaction. Multivariate analysis further confirms that high electronic conductivity and optimal surface oxygen vacancy concentration correlate with increased selectivity towards partial oxidation products such as methanol, acetaldehyde, and propanal. The integration of electronic structure tuning, controlled synthesis, and operando spectroscopic characterization provides a rational framework for designing spinel-type catalysts with tailored activity and selectivity for light alkane oxidation. These findings offer valuable mechanistic insights and highlight the potential of rationally engineered mixed metal spinels for industrial applications in energy-efficient alkane valorization.