Photoreduction of CO2 into sustainable and green solar fuels is generally believed to be an appealing solution to simultaneously overcome both environmental problems and energy crisis. The low selectivity of challenging multi-electron CO2 photoreduction reactions makes it one of the holy grails in heterogeneous photocatalysis. This Review highlights the important roles of cocatalysts in selective photocatalytic CO2 reduction into solar fuels using semiconductor catalysts. A special emphasis in this review is placed on the key role, design considerations and modification strategies of cocatalysts for CO2 photoreduction. Various cocatalysts, such as the biomimetic, metal-based, metal-free, and multifunctional ones, and their selectivity for CO2 photoreduction are summarized and discussed, along with the recent advances in this area. This Review provides useful information for the design of highly selective cocatalysts for photo(electro)reduction and electroreduction of CO2 and complements the existing reviews on various semiconductor photocatalysts.

Cocatalysts for Selective Photoreduction of CO2 into Solar Fuels.

Code and data for "Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1"

Hydrogen generation from the direct splitting of water by photocatalysis is regarded as a promising and renewable solution for the energy crisis The key to realize this reaction is to find an efficient and robust photocatalyst that ideally makes use of the energy from sunlight Recently, due to the attractive properties such as appropriate band structure, ultrahigh specific surface area, and more exposed active sites, two-dimensional (2D) photocatalysts have attracted significant attention for photocatalytic water splitting This Review attempts to summarize recent progress in the fabrication and applications of 2D photocatalysts including graphene-based photocatalysts, 2D oxides, 2D chalcogenides, 2D carbon nitride, and some other emerging 2D materials for water splitting The construction strategies and characterization techniques for 2D/2D photocatalysts are summarized Particular attention has been paid to the role of 2D/2D interfaces in these 2D photocatalysts as the interfaces and heterojunctions a

Role of Interfaces in Two-Dimensional Photocatalyst for Water Splitting

In this work, uniform molybdenum disulfide (MoS2)/tungsten disulfide (WS2) quantum dots are synthesized by the combination of sonication and solvothermal treatment of bulk MoS2/WS2 at a mild temperature. The resulting products possess monolayer thickness with an average size about 3 nm. The highly exfoliated and defect-rich structure renders these quantum dots plentiful active sites for the catalysis of hydrogen evolution reaction (HER). The MoS2 quantum dots exhibit a small HER overpotential of ≈120 mV and long-term durability. Moreover, the strong fluorescence, good cell permeability, and low cytotoxicity make them promising and biocompatible probes for in vitro imaging. In addition, this work may provide an alternative facile approach to synthesize the quantum dots of transition metal dichalcogenides or other layered materials on a large scale.

One‐Pot, Facile, and Versatile Synthesis of Monolayer MoS 2 /WS 2 Quantum Dots as Bioimaging Probes and Efficient Electrocatalysts for Hydrogen Evolution Reaction

Two new imide-based crystalline, porous, and chemically stable covalent organic frameworks (COFs) (TpBDH and TfpBDH) have been successfully synthesized employing solvothermal crystallization route. Furthermore, thin layered covalent organic nanosheets (CONs) were derived from these bulk COFs by the simple liquid phase exfoliation method. These 2D CONs showcase increased luminescence intensity compared to their bulk counterparts (COFs). Notably, TfpBDH-CONs showcase good selectivity and prominent, direct visual detection towards different nitroaromatic analytes over TpBDH-CONs. Quite interestingly, TfpBDH-CONs exhibit a superior “turn-on” detection capability for 2,4,6-trinitrophenol (TNP) in the solid state, but conversely, they also show a “turn-off” detection in the dispersion state. These findings describe a new approach towards developing an efficient, promising fluorescence chemosensor material for both visual and spectroscopic detection of nitroaromatic compounds with very low [10−5 (M)] analyte concentrations.

/pdf/chemical-sensing-in-two-dimensional-porous-covalent-organic-3yjfdv140k.pdf

Chemical sensing in two dimensional porous covalent organic nanosheets.

Molybdenum disulfide (MoS2) is a promising non-precious-metal catalyst, but its performance is limited by the density of active sites and poor electrical transport. Its metallic 1T phase possesses higher photoelectrocatalytic activity. Thus, how to efficiently increase the concentration of the 1T phase in the exfoliated two-dimensiaonal (2D) MoS2 nanosheets is an important premise. In this work, we propose a strategy to prepare a 2D heterostructure of MoS2 nanosheets using supercritical CO2-induced phase engineering to form metallic 1T-MoS2. Theoretical calculations and experimental results demonstrate that the introduced CO2 in the 2H-MoS2 host can prompt the transformation of partial 2H-MoS2 lattices into 1T-MoS2. Moreover, the electrical coupling and synergistic effect between 2H and 1T phases can greatly facilitate the efficient electron transfer from the active sites of MoS2, which significantly improves the photocatalytic performance.

CO2-Induced Phase Engineering: Protocol for Enhanced Photoelectrocatalytic Performance of 2D MoS2 Nanosheets

As a remarkable class of plasmonic materials, two dimensional (2D) semiconductor compounds have attracted attention owing to their controlled manipulation of plasmon resonances in the visible light spectrum, which outperforms conventional noble metals. However, tuning of plasmonic resonances for 2D semiconductors remains challenging. Herein, we design a novel method to obtain amorphous molybdenum oxide (MoO3 ) nanosheets, in which it combines the oxidation of MoS2 and subsequent supercritical CO2 -treatment, which is a crucial step for the achievement of amorphous structure of MoO3 . Upon illumination, hydrogen-doped MoO3 exhibits tuned surface plasmon resonances in the visible and near-IR regions. Moreover, a unique behavior of the amorphous MoO3 nanosheets has been found in an optical biosensing system; there is an optimum plasmon resonance after incubation with different BSA concentrations, suggesting a tunable plasmonic device in the near future.

CO2‐Assisted Fabrication of Two‐Dimensional Amorphous Molybdenum Oxide Nanosheets for Enhanced Plasmon Resonances

A green route to fabricate MoS2 nanosheets in water–ethanol–CO2

As coronavirus disease 2019 (COVID-19) continues to spread, a detailed understanding on the transmission mechanisms is of paramount importance. The disease transmits mainly through respiratory droplets and aerosol. Although models for the evaporation and trajectory of respiratory droplets have been developed, how the environment impacts the transmission of COVID-19 is still unclear. In this study, we investigate the propagation of respiratory droplets and aerosol particles generated by speech under a wide range of temperatures (0-40 °C) and relative humidity (0-92%) conditions. We show that droplets can travel three times farther in low-temperature and high-humidity environment, whereas the number of aerosol particles increases in high-temperature and low-humidity environments. The results also underscore the importance of proper ventilation, as droplets and aerosol spread significantly farther in airstreams. This study contributes to the understanding of the environmental impact on COVID-19 transmission.

COVID-19: Effects of Environmental Conditions on the Propagation of Respiratory Droplets.

MoS2 nanosheets with polydispersity of the lateral dimensions from natural mineral molybdenite have been prepared in the emulsions microenvironment built by the water/surfactant/CO2 system. The size, thickness, and atomic structure are characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and laser-scattering particle size analysis. Meanwhile, by the analysis of photoluminescence spectroscopy and microscope, the MoS2 nanosheets with smaller lateral dimensions exhibit extraordinary photoluminescence properties different from those with relatively larger lateral dimensions. The discovery of the excitation dependent photoluminescence for MoS2 nanosheets makes them potentially of interests for the applications in optoelectronics and biology. Moreover, we demonstrate that the fabricated MoS2 nanosheets can be a nontoxic fluorescent label for cell-targeted labeling application.

Yuhang Qi

Papers

CO2-Induced Phase Engineering: Protocol for Enhanced Photoelectrocatalytic Performance of 2D MoS2 Nanosheets

CO2‐Assisted Fabrication of Two‐Dimensional Amorphous Molybdenum Oxide Nanosheets for Enhanced Plasmon Resonances

A green route to fabricate MoS2 nanosheets in water–ethanol–CO2

COVID-19: Effects of Environmental Conditions on the Propagation of Respiratory Droplets.

Synthesis of strongly fluorescent molybdenum disulfide nanosheets for cell-targeted labeling.