Optimized <i>e</i> _<i>g</i> orbitals of Mn enable <scp> H ₂ O </scp> activation for low‐temperature <scp>HCHO</scp> oxidation over atomically Nb‐doped <scp> MnO ₂ </scp>

Abstract Enhancing low‐temperature activity of metal oxides in gas‐solid catalysis remains a significant challenge. Here, we propose a single‐atom niobium (Nb) regulation strategy to optimize the d‐electron structure of manganese in MnO 2 catalysts for 200 ppm formaldehyde oxidation with 37.5% relative humidity. The Nb‐doped MnO 2 demonstrates remarkable catalytic performance, lowering T 90 (the temperature at which 90% conversion is reached) by 42 °C compared to undoped MnO 2 . This enhancement originates from directional control of d‐orbital splitting energy and optimized e g orbital filling of Mn, which collectively reduces the electron‐transfer barrier during the reaction. In situ characterization and DFT calculation also reveal a synergistic adsorption configuration where HCHO and H 2 O molecules form an electron relay transfer network. Our work establishes atomic‐level electronic structure engineering as an effective approach to improve catalytic efficiency, while the identified electron relay mechanism provides fundamental insights into the metal oxide interface interactions for heterogeneous catalytic systems.