Light-Induced Dynamic Restructuring of Cu Active Sites on TiO2 for Low-Temperature H2 Production from Methanol and Water.

The structure and configuration of reaction centers, which dominantly govern the catalytic behaviors, often undergo dynamic transformations under reaction conditions, yet little is known about how to exploit these features to favor the catalytic functions. Here, we demonstrate a facile light activation strategy over a TiO2-supported Cu catalyst to regulate the dynamic restructuring of Cu active sites during low-temperature methanol steam reforming. Under illumination, the thermally deactivated Cu/TiO2 undergoes structural restoration from inoperative Cu2O to the originally active metallic Cu caused by photoexcited charge carriers from TiO2, thereby leading to substantially enhanced activity and stability. Given the low-intensity solar irradiation, the optimized Cu/TiO2 displays a H2 production rate of 1724.1 µmol g-1 min-1, outperforming most of the conventional photocatalytic and thermocatalytic processes. Taking advantages of the strong light-matter-reactant interaction, we achieve in situ manipulation of the Cu active sites, suggesting the feasibility for real-time functionalization of catalysts.

Co-sintering process of LiCoO2 cathodes and NASICON-type LATP solid electrolytes studied by X-ray diffraction and X-ray absorption near edge structure.

The composites of a high-capacity cathode material in lithium-ion batteries, LiCoO2 (LCO) and an oxide-based solid electrolyte, Li1.3Al0.3Ti1.7(PO4)3 (LATP), were sintered at various temperatures and their reaction products were subsequently identified by X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES). Rietveld analysis of XRD and the linear combination fitting of XANES showed that the reaction of LCO and LATP proceeds via three major steps; from 300 °C to 500 °C, LCO and LATP react with each other to form Co3O4, amorphous TiO2 and Li3PO4; from 500 °C at which crystalline LCO is completely decomposed, LATP reacts not only with remaining amorphous/low crystalline LCO but also with Co3O4 to form LiCoPO4 and TiO2; from 700 °C to 750 °C, Co3O4 and TiO2 react with each other to form CoTiO3. The final products at 900 °C are LiCoPO4, CoTiO3, TiO2, and Li3PO4.

Stabilizing Atomically Dispersed Catalytic Sites on Tellurium Nanosheets with Strong Metal-Support Interaction Boosts Photocatalysis.

The utilization of appropriate supports for constructing single-atom-catalysts is of vital importance to achieve high catalytic performances, as the strong mutual interactions between the atomically dispersed metal atoms and supports significantly influence their electronic properties. Herein, it is reported that atomic cobalt species (ACS) anchored 2D tellurium nanosheets (Te NS) can act as a highly active single-atom cocatalyst for boosting photocatalytic H2 production and CO2 reduction reactions under visible light irradiation, wherein Te NS serves as the ideal support material to bridge the light absorbers and ACS catalytic sites for efficient electron transfer. X-ray absorption near-edge structure spectroscopy reveals that the ACS are built by a Co center coordinated with five CoO bonding, which are anchored on Te NS through one CoTe bonding. The strong mutual interaction between the Te NS and ACS alters the electronic structure of Te NS, inducing the introduction of intermediate energy states, which act as trap sites to accommodate the photogenerated electrons for promoting photocatalytic reactions. This work may inspire further capability in designing other Te-based single-atom-catalysts for highly efficient solar energy conversion.

Intermolecular cascaded π-conjugation channels for electron delivery powering CO2 photoreduction.

Photoreduction of CO2 to fuels offers a promising strategy for managing the global carbon balance using renewable solar energy. But the decisive process of oriented photogenerated electron delivery presents a considerable challenge. Here, we report the construction of intermolecular cascaded π-conjugation channels for powering CO2 photoreduction by modifying both intramolecular and intermolecular conjugation of conjugated polymers (CPs). This coordination of dual conjugation is firstly proved by theoretical calculations and transient spectroscopies, showcasing alkynyl-removed CPs blocking the delocalization of electrons and in turn delivering the localized electrons through the intermolecular cascaded channels to active sites. Therefore, the optimized CPs (N-CP-D) exhibiting CO evolution activity of 2247 µmol g-1 h-1 and revealing a remarkable enhancement of 138-times compared to unmodified CPs (N-CP-A).

Synergetic Exfoliation and Lateral Size Engineering of MoS2 for Enhanced Photocatalytic Hydrogen Generation.

Generally, exfoliation is an efficient strategy to create more edge site so as to expose more active sites on molybdenum disulphide (MoS2 ). However, the lateral sizes of the resultant MoS2 monolayers are relatively large (≈50-500 nm), which retain great potential to release more active sites. To further enhance the catalytic performance of MoS2 , a facile cascade centrifugation-assisted liquid phase exfoliation method is introduced here to fabricate monolayer enriched MoS2 nanosheets with nanoscale lateral sizes. The as-prepared MoS2 revealed a high monolayer yield of 36% and small average lateral sizes ranging from 42 to 9 nm under gradient centrifugations, all exhibiting superior catalytic performances toward photocatalytic H2 generation. Particularly, the optimized monolayer MoS2 with an average lateral size of 9 nm achieves an apparent quantum efficiency as high as 77.2% on cadmium sulphide at 420 nm. This work demonstrates that the catalytic performances of MoS2 could be dramatically enhanced by synergistic exfoliation and lateral size engineering as a result of increased density of active sites and shortened charge diffusion distance, paving a new way for design and fabrication of transition-metal dichalcogenides-based materials in the application of hydrogen generation.