Noble Metal-Free FeOOH/Li0.1WO3 Core-Shell Nanorods for Selective Oxidation of Methane to Methanol with Visible-NIR Light

Hydroxyl radicals ((OH)-O-center dot) generated in the photocatalytic process are crucial to the conversion of methane (CH4) to value-added methanol (CH3OH) at room temperature. However, utilizing noble metal-free catalysts and low-energy photons of solar light, such as visible and near-infrared light (vis-NIR), is difficult to provide more electron states to form (OH)-O-center dot radicals. Here, we developed FeOOH/Li0.1WO3 core-shell nanorods via a two-step in/out co-modification of hexagonal tungsten oxide (h-WO3): (1) lithium ions intercalating into the hexagonal tunnels of h-WO3 to form Li0.1WO3 nanorods and (2) using FeOOH-wrapped Li0.1WO3 to obtain FeOOH/Li0.1WO3 core-shell nanorods. Introduction of lithium induces polaron transition in Li0.1WO3, enabling the absorption of vis-NIR light. Interestingly, FeOOH-based Fenton-like reaction when H2O2 is selected as an oxidant favors the generation of more (OH)-O-center dot radicals available for CH4 oxidation to CH3OH. Meanwhile, FeOOH with Fe-III as an electron sink highly improves the separation of photoinduced electrons and holes in Li0.1WO3. Eventually, efficient selective formation of CH4OH is achieved with remarkable generation rates up to similar to 342 and similar to 160 mu mol g(-1) at visible light (420-700 nm) and NIR light (>= 800 nm), respectively. Our finding opens up new possibilities for developing noble metal-free catalysts for solar energy-driven CH4 conversion to CH3OH under ambient conditions.

Automated summary

The study developed FeOOH/Li0.1WO3 core-shell nanorods to enhance the efficiency of photocatalytic conversion of methane to methanol. The introduction of lithium ions and the FeOOH-based Fenton-like reaction increased the generation of (OH)· radicals, leading to efficient formation of CH4OH under visible and near-infrared light.