Radially oriented mesoporous TiO2 microspheres with single-crystal–like anatase walls for high-efficiency optoelectronic devices

Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m2/g), a large pore volume (0.164 cm3/g), and highly single-crystal–like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.State Key Basic Research Program of China (2013CB934104 and 2012CB224805), the National Science Foundation (21210004), the Science and Technology Commission of Shanghai Municipality (08DZ2270500), the Shanghai Leading Academic Discipline Project (B108), King Abdulaziz City for Science and Technology (project no. 29-280), and Deanship of Scientific Research, King Saud University–The International Highly Cited Research Group Program (IHCRG#14-102). Y.L. also acknowledges the Interdisciplinary Outstanding Doctoral Research Funding of Fudan University (EZH2203302/001)

Study on the influence of goaf filling on surface deformation in loess gully area

In order to study the influence of different filling schemes on overlying rock and surface deformation under the influence of topographic conditions, according to the mining and geological conditions of Luzigou Coal Mine, many kinds of numerical models of filling schemes considering topographic factors are simulated and analyzed by FLAC3D software, and the deformation and failure characteristics of goaf roof and surface under different filling rates and filling positions are analyzed, and the stable effects of different filling schemes on goaf are obtained. The results show that the surface displacement decreases with the increase of filling rate; when the filling rate is between 20% and 70%, the filling effect increases obviously with the increase of filling rate, and there is an approximate linear negative correlation between the maximum total displacement and the filling rate; when the filling rate is less than 20% or more than 70%, the change of filling rate has little effect on the filling effect; interval filling can change the shape of surface subsidence basin; when the filling volume is kept at a certain amount, the surface settlement of interval filling scheme is smaller and the filling effect is better. The horizontal displacement of the surface slope affected by the goaf under the filling valley is smaller than that under the filling peak, and the possibility of slope instability is less

Rational Assembly of the NiMoP/NiCoZn Heterostructure Electrocatalyst for the Hydrogen Evolution Reaction at High Current Densities

Developing a cost-effective hydrogen (H2) evolution electrocatalyst can effectively solve the problem of environmental pollution caused by excessive fossil fuel use. Herein, we report an innovative synthetic strategy, involving hydrothermal electrodeposition of a NiCoZn film on commercial carbon fiber paper (CFP) and in situ cyclic voltammetric electrodeposition of NiMoP to prepare a heterostructure electrocatalyst (NiMoP/NiCoZn/CFP) with synergistic electrocatalytic activity toward the hydrogen evolution reaction (HER). To deliver high current densities of 500 and 1000 mA cm–2, the NiMoP/NiCoZn/CFP electrode only required overpotentials of 230 and 268 mV, respectively, which were considerably superior to those of Pt–C/CFP (457 and 592 mV, respectively). Moreover, this electrode exhibited excellent ultrastability (40 h at 500 mA cm–2 or 80 h at 1 A cm–2). The superior electrocatalytic HER activity is attributed to (1) cooperative electronic interactions between NiMoP and NiCoZn in the heterointerface and (2) the complete wettability, which is advantageous for gas formation and desorption and considerably reduces bubble adhesion and reaction resistance. This work provides a rational electrodeposition strategy for constructing heterointerface electrocatalysts for H2 production at high current densities

Rational Assembly of the NiMoP/NiCoZn Heterostructure Electrocatalyst for the Hydrogen Evolution Reaction at High Current Densities

Developing a cost-effective hydrogen (H2) evolution electrocatalyst can effectively solve the problem of environmental pollution caused by excessive fossil fuel use. Herein, we report an innovative synthetic strategy, involving hydrothermal electrodeposition of a NiCoZn film on commercial carbon fiber paper (CFP) and in situ cyclic voltammetric electrodeposition of NiMoP to prepare a heterostructure electrocatalyst (NiMoP/NiCoZn/CFP) with synergistic electrocatalytic activity toward the hydrogen evolution reaction (HER). To deliver high current densities of 500 and 1000 mA cm–2, the NiMoP/NiCoZn/CFP electrode only required overpotentials of 230 and 268 mV, respectively, which were considerably superior to those of Pt–C/CFP (457 and 592 mV, respectively). Moreover, this electrode exhibited excellent ultrastability (40 h at 500 mA cm–2 or 80 h at 1 A cm–2). The superior electrocatalytic HER activity is attributed to (1) cooperative electronic interactions between NiMoP and NiCoZn in the heterointerface and (2) the complete wettability, which is advantageous for gas formation and desorption and considerably reduces bubble adhesion and reaction resistance. This work provides a rational electrodeposition strategy for constructing heterointerface electrocatalysts for H2 production at high current densities

Recent progress in short- to long-wave infrared photodetection using 2D materials and heterostructures

The extraordinary electronic, optical, and mechanical characteristics of 2D materials make them promising candidates for optoelectronics, specifically in infrared (IR) detectors owing to their flexible composition and tunable optoelectronic properties. This review presents the recent progress in IR detectors composed of 2D materials and their hybrid structures, including graphene, black phosphorous, transition metal dichalcogenides, halide perovskite as well as other new layered materials and their heterostructures. The focus is on the short-wave, mid-wave, and long-wave infrared regimes, which pose a grand challenge for rational materials and device designs. The dependence of the device performance on the optical and electronic properties of 2D materials is extensively discussed, aiming to present the general strategies for designing optoelectronic devices with optimal performance. Furthermore, the recent results on 2D material-based heterostructures are presented with an emphasis on the relationship between band alignment, charge transfer, and IR photodetection. Finally, a summary is given as well as the discussion of existing challenges and future directions.Ministry of Education (MOE)National Research Foundation (NRF)X.G., X.Y., and D.P. contributed equally to this work. The authors thank the support from Singapore National Research Foundation, Competitive Research Program (NRF-CRP18-2017-02 and NRF–CRP19–2017–01), A*Star AME Programmatic Grant under Grant A18A7b0058, Singapore Ministry of Education Tier 2 Program (MOE2016-T2-1-128), and National Natural Science Foundation of China (61704082) and Natural Science Foundation of Jiangsu Province (BK20170851)

The Deformations of Carbon Nanotubes under Cutting

The determination of structural evolution at the atomic level is essential to understanding the intrinsic physics and chemistries of nanomaterials. Mechanochemistry represents a promising method to trace structural evolution, but conventional mechanical tension generates random breaking points, which makes it unavailable for effective analysis. It remains difficult to find an appropriate model to study shear deformations. Here, we synthesize high-modulus carbon nanotubes that can be cut precisely, and the structural evolution is efficiently investigated through a combination of geometry phase analysis and first-principles calculations. The lattice fluctuation depends on the anisotropy, chirality, curvature, and slicing rate. The strain distribution further reveals a plastic breaking mechanism for the conjugated carbon atoms under cutting. The resulting sliced carbon nanotubes with controllable sizes and open ends are promising for various applications, for example, as an anode material for lithium-ion batteries