Elucidating the Volcanic-Type Catalytic Behavior in Lithium-Sulfur Batteries via Defect Engineering.

Defects are generally considered to be effective and flexible in the catalytic reactions of lithium-sulfur batteries. However, the influence of the defect concentration on catalysis remains ambiguous. In this work, molybdenum sulfide with different sulfur vacancy concentrations is comprehensively modulated, showing that the defect level and the adsorption-catalytic performance result in a volcano relationship. Moreover, density functional theory and in situ experiments reveal that the optimal level of sulfur defects can effectively increase the binding energy between molybdenum sulfide and lithium polysulfides (LiPSs), lower the energy barrier of the LiPS conversion reaction, and promote the kinetics of Li2S bidirectional catalytic reaction. The lower bidirectional catalytic performance incited by excessive or deficient sulfur defects is mainly due to the deformed geometrical structures and reduced adsorption of key LiPSs on the catalyst surface. This work underscores the imperative of controlling the defect content and provides a potential approach to the commercialization of lithium-sulfur batteries.

Black Arsenic-Phosphorus Nanosheets for Highly Responsive Photodetection and Dual-Wavelength Ultrafast Pulse Generation at Telecommunication Bands.

Black arsenic-phosphorus (b-AsP), an alloy containing black phosphorus and arsenic in the form of b-AsxP1-x, has a broadly tunable band gap changing with the chemical ratios of As and P. Although mid-infrared photodetectors and mode-locked or Q-switched pulse lasers based on b-AsP (mostly b-As0.83P0.17) are investigated, the potential of this family of materials for near-infrared photonic and optoelectronic applications at telecommunication bands is not fully explored. Here, we have verified a multifunctional fiber device based on b-As0.4P0.6 nanosheets for highly responsive photodetection and dual-wavelength ultrafast pulse generation at around 1550 nm. The fiber laser with a saturable absorber (SA) based on b-As0.4P0.6 nanosheets can output dual-wavelength mode-locking pulses with a larger bandwidth and spectral separation than those based on other two-dimensional (2D) materials. Remarkably, it is found that the b-As0.4P0.6-based photodetector can achieve a high responsivity of 10,200 A/W at 1550 nm and a peak responsivity of 2.29 × 105 A/W at 980 nm. Our work suggests that b-As0.4P0.6 shows great potential in ultrafast photonics, dual-comb spectroscopy, and infrared signal detection.

Inert V2O3 oxide promotes the electrocatalytic activity of Ni metal for alkaline hydrogen evolution.

Here, we develop inert V2O3 oxide to enhance the HER activity of industrial Ni catalysts with the assistance of abundant metal/oxide interfaces. The as-synthesized Ni/V2O3 catalyst exhibits over 5 times the activity of a pure Ni sample due to the particle size control and metal/oxide interaction, and excellent durability as a result of oxide anchoring.