In Situ Generated Asymmetric Charge‐Polarized Pd δ− ‐O δ− ‐Zn Sites for Highly Selective Photocatalytic Oxidation of Methane to Formaldehyde

ABSTRACT Direct conversion of CH 4 into liquid oxygenates remains a great challenge due to the inert C─H bond and the difficulty in achieving unity selectivity toward C1 liquid oxygenates. Current photocatalytic systems mainly focus on C─H activation, while the continuous conversion of oxygenated intermediates toward desired products is rarely addressed. Herein, we propose a mechanism mediated by electronically asymmetric and polarized interfacial Pd‐O‐Zn sites (Pd δ− ‐O δ− ‐Zn) that inhibit the reverse hydrogenation of methoxy ( * OCH 3 ) intermediates, thereby enabling highly efficient direct conversion of CH 4 to HCHO. In situ spectroscopic characterizations combined with DFT calculations uncovered that, compared with Pd NPs‐ZnO, the construction of Pd δ− ‐O δ− ‐Zn sites significantly lowers the C─H bond activation barrier of CH 4 (from 0.08 to −0.1 eV). Meanwhile, the strong Pd d‐O p orbital interactions facilitate CH 3 OH dehydrogenation to form * OCH 3 intermediates. More encouragingly, these Pd δ− ‐O δ− ‐Zn sites effectively promote * OCH 3 dehydrogenation to HCHO, thereby suppressing the reverse hydrogenation pathway that regenerates CH 3 OH. As a result, PdZn‐ZnO delivers an excellent HCHO yield of 8320.5 µmol·g −1 h −1 with a selectivity of 91.6% at room temperature. This work provides a novel strategy for the rational design of high‐performance photocatalysts for the highly selective conversion of CH 4 into HCHO.