Core–Shell Interface Effect for Boosting Selective Oxidation of Methane to Formaldehyde Over Cu/SiO ₂ @TiO ₂ Catalyst

ABSTRACT The selective oxidation of methane to formaldehyde presents a formidable challenge due to the inherent stability of methane and the tendency for overoxidation. Herein, we report core–shell structured 1% Cu/m‐SiO 2 @TiO 2 ‐ x catalysts designed to enhance catalytic performance for the selective oxidation of methane. The incorporation of a TiO 2 coating was found to play a critical role in modulating the dispersion of copper species and the surface chemical microenvironment. Characterization techniques revealed that the TiO 2 layer modulates the surface chemical environment, promoting the formation of Si–O–Ti interfaces and influencing the electronic interaction among Cu, Ti, and Si. The Si–O–Ti interface was identified as crucial for anchoring highly dispersed CuO x clusters, optimizing oxygen vacancy generation, and regulating reactive oxygen species. Consequently, this tailored interface suppressed the overoxidation of formaldehyde, leading to improved formaldehyde selectivity while maintaining comparable methane conversion. The optimized catalyst (1% Cu/m‐SiO 2 @TiO 2 ‐1) achieved a formaldehyde yield of 1.3% at 700°C, with significantly improved selectivity compared with its unmodified counterpart (1% Cu/m‐SiO 2 ). This work highlights the importance of interface engineering in catalyst design and provides a viable strategy for developing efficient catalysts for the direct conversion of methane to formaldehyde.