Single-atom catalysts for photocatalytic energy conversion

Research progress on methane conversion coupling photocatalysis and thermocatalysis

Photocatalysis is a promising strategy for addressing carbon emissions and energy challenges. 3D nanostructures have aroused enormous attention due to their high reaction area, in which three-dimensionally ordered macroporous (3DOM) materials are of particular interest to researchers for their larger specific surface area, high light absorption and stability, outstanding mass transfer performance, and unique physicochemical property. Therefore, 3DOM materials have been widely studied in photocatalytic energy conversion and environmental protection such as pollutants degradation, water splitting, and carbon dioxide reduction. In addition, the design method of 3DOM materials also determines the photocatalytic ability. Herein, in this overview, the ongoing progresses in the fabrication and applications of 3DOM materials in photocatalysis are comprehensively summarized and reviewed. Meanwhile, the unique advantages and proposed mechanism of 3DOM materials in photocatalytic processes are discussed in depth. Subsequently, the urgent challenges and future perspectives of 3DOM materials in the photocatalytic system are proposed. We eagerly hope that this review can promote and facilitate the rapid progress of this dynamic research field.

Three-dimensional ordered macroporous materials for photocatalysis: design and applications

Atomic-Scale Pd on 2D Titania Sheets for Selective Oxidation of Methane to Methanol

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.

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

Visible-light driven room-temperature coupling of methane to ethane by atomically dispersed Au on WO3

Atomic-scale metals as active center have been widely investigated for efficient photocatalysis. Understanding the specific electronic structure of atomic-scale center is of frofound fundamental importance for superior catalytic performance. Here, we report an atomically dispersed gold on tungsten trioxide (Au1/WO3) catalyst for photocatalytic oxidation of methane toward value-added methanol. The Au1 species reveal a specific tip-enhanced local electrons field which favors the C-H dehydrogenation of methane and thus form methanol (up to 589 µmol g-1 h-1). Both experimental and theoretical results demonstrate such tip-enhanced effect-dependent activity of methane oxidation. The theoretical calculations further reveal a lower adsorption energy of product methanol on Au1, in contrast to Au particles, which suppresses the overoxidation of methanol, and thus promotes its selectivity. Establishing the electric structure-activity may create a platform for designing efficient atomic-scale catalysts for C1 catalysis and green chemistry.

Zhiyuan Tang

Papers

Visible-light driven room-temperature coupling of methane to ethane by atomically dispersed Au on WO3

Photocatalytic Oxidation of Methane to Methanol by Tungsten Trioxide-supported Atomic Gold at Room Temperature