Noble Metal-Free FeOOH/Li_0.1WO₃ Core–Shell Nanorods for Selective Oxidation of Methane to Methanol with Visible–NIR Light

Abstract

Hydroxyl radicals (•OH) 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 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 radicals available for CH4 oxidation to CH3OH. Meanwhile, FeOOH with FeIII 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 ∼342 and ∼160 μmol 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.

Selective Photocatalytic Oxidation of Methane to Oxygenates over Cu–W–TiO2 with Significant Carrier Traps

“…With the addition of H 2 O 2 , an alcohol selectivity of 97% was obtained over FeO x /TiO 2 . Also, the generation rate of CH 3 OH was up to 342 μmol g –1 with H 2 O 2 as the oxidant under visible-light irradiation over FeOOH/Li 0.1 WO 3 . However, the unsatisfactory photocatalytic activity, usage of expensive noble metals or H 2 O 2 , and relatively low utilization efficiency of visible light hinder the large-scale application of methane conversion.…”

Solar Photocatalytic Oxidation of Methane to Methanol with Water over RuOx/ZnO/CeO2 Nanorods

“…As the main component of natural gas, methane (CH 4 ) is widely distributed around the world as a fuel and has drawn considerable attention as a promising resource for the production of high-value chemical commodities, such as methanol (CH 3 OH), hydrogen, and olefins. − However, due to its stable and inert molecular configuration, the current industrial route for CH 4 transformation suffers from intense energy consumption and considerable CO 2 emission. Therefore, developing novel technologies for CH 4 conversion with high efficiency, low cost, and in an environmentally friendly fashion is extremely desirable. , Photocatalytic CH 4 conversion driven by clean and abundant solar energy could achieve the C–H activation at room temperature, representing a new stimulus for CH 4 conversion .…”

“…Therefore, developing novel technologies for CH 4 conversion with high efficiency, low cost, and in an environmentally friendly fashion is extremely desirable. , Photocatalytic CH 4 conversion driven by clean and abundant solar energy could achieve the C–H activation at room temperature, representing a new stimulus for CH 4 conversion . To date, two main technical routes have been reported in the solar-energy-mediated CH 4 conversion to different products: (i) nonoxidative coupling to generate ethane and hydrogen and (ii) reacting with oxygen, water, and hydrogen peroxide to produce CH 3 OH, hydrogen, and carbon monoxide. , Among various products of CH 4 conversion, CH 3 OH is one of the most preferred products because it not only could act as versatile C1 building blocks for higher-value chemicals in the chemical industry but it also is a promising fuel due to the high energy density. ,, …”

Photothermal Synergistic Effect of Pt1/CuO-CeO2 Single-Atom Catalysts Significantly Improving Toluene Removal

“…37,58 Reactive oxygen species( • OH and • O 2 − ) further promote the surface oxidation process, leading to a rapid transformation of the intermediates and accelerated release of the active sites to further accelerate the reactions. 4,37 Combined with the GC-MS results, we deduce that the main reaction pathways of toluene in photothermocatalytic and thermocatalytic processes might be: toluene → benzyl alcohol → benzene and xylene → benzoic acid and benzaldehyde → itaconic anhydride and maleic anhydride → short-chain alcohols → carbon dioxide and water (Figure 5).…”