Abstract
ABSTRACT
Direct photocatalytic conversion of methane to formaldehyde is highly efficient, avoiding energy‐intensive methanol oxidation. However, its selectivity and activity are severely limited by uncontrollable over‐oxidation: Formaldehyde has lower C‐H dissociation energy than methane, prone to deep overoxidation to CO
2
. Herein, we report H/WO
2.72
hydrogenated nonstoichiometric tungsten oxide photocatalyst. At ambient temperature, it attains 100% HCHO selectivity over all detectable carbonaceous products at 30.94 µmol·h
−1
, with 11‐fold higher activity than commercial WO
3
and outperforming most conventional photocatalysts. Operando spectroscopic studies and density functional theory (DFT) calculations reveal that surface W‐H bonds act as a kinetically gated “Anti‐Overoxidation valve,” W–H bonds are preferentially cleaved by reactive oxygen species (·OOH), as they are thermodynamically weaker than the C–H bonds in HCHO and its over‐oxidation intermediate (*HCOOH). Then the generated hydrogen radicals (H*) drive a reverse reduction pathway to convert the *HCOOH back to *HCHO, interrupting deep oxidation. Concurrently, hydrogenation optimizes the electronic structure of WO
2.72
, lowering the HCHO desorption barrier to facilitate timely product release. This work provides a dynamic strategy for complete selectivity in catalytic CH
4
conversion, emphasizing the value of precise kinetic pathway modulation for methane valorization.