Macroporous silicon microreactor for the preferential oxidation of CO

A macroporous silicon micromonolith containing ca. 40,000 regular channels of 3.3 μm in diameter per square millimeter has been successfully functionalized with an Au/TiO₂ catalyst for CO preferential oxidation (CO-PrOx) in the presence of hydrogen. The functionalization of the silicon microchannels has been accomplished by growing a SiO₂ layer on the channel walls, followed by exchange with a titanium alkoxyde precursor and decomposition into TiO₂ and, finally, by anchoring carbosilanethiol dendron protected pre-formed Au nanoparticles. Catalytically active centers at the Au-TiO₂ interface have been obtained by thermal activation. With this method, an excellent homogeneity and adherence of the catalytic layer over the microchannels of the macroporous silicon micromonolith has been obtained, which has been tested for CO-PrOx at 363-433 K and λ=2 under H₂/CO=0-20 (molar). The macroporous silicon micromonolith converts ca. 3 NmL of CO per minute and mL of micro reactor at 433 K under H₂/CO=20, suggesting that it could be particularly effective for hydrogen purification in low-temperature microfuel cells for portable applications.