Efficient electrooxidation of biomass-derived aldehydes over ultrathin Ni V-layered double hydroxides films

Selective upgrading of C=O bonds to afford carboxylic acid is significant for the petrochemical industry and biomass utilization.Here we declared the efficient electrooxidation of biomass-derived aldehydes family over NiV-layered double hydroxides(LDHs) thin films.Mechanistic studies confirmed the hydroxyl active intermediate(-OH*) generated on the surface of NiV-LDHs films by employing electrochemical impedance spectroscopy and the electron paramagnetic resonance spectroscopy.By using advanced techniques,e.g.,extended X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy,NiV-LDHs films with 2.6 nm could expose larger specific surface area.Taking benzaldehyde as a model,high current density of 200 mA cm^(-2)at 1.8 V vs.RHE,81.1% conversion,77.6% yield of benzoic acid and 90.8% Faradaic efficiency were reached,which was superior to most of previous studies.Theoretical DFT analysis was well matched with experimental findings and documented that NiV-LDHs had high adsorption capacity for the aldehydes to suppress the side reaction,and the aldehydes were oxidized by the electrophilic hydroxyl radicals formed on NiV-LDHs.Our findings offer a universal strategy for the robust upgrading of diverse biomass-derived platform chemicals.

Whispering-gallery-mode barcode-based broadband sub-femtometer-resolution spectroscopy with an electro-optic frequency comb

Spectroscopy is the basic tool for studying molecular physics and realizing biochemical sensing.However,it is challenging to realize sub-femtometer resolution spectroscopy over broad bandwidth.Broadband and high-resolution spectroscopy with calibrated optical frequency is demonstrated by bridging the fields of speckle pattern and electro-optic frequency comb.A wavemeter based on a whispering-gallery-mode barcode is proposed to link the frequencies of a probe continuous-wave laser and an ultrastable laser.The ultrafine electro-optic comb lines are generated from the probe laser to record spectrum of sample with sub-femtometer resolution.Measurement bandwidth is a thousandfold broader than comb bandwidth,by sequentially tuning the probe laser while its wavelength is determined.This approach fully exploits the advantages of two fields to realize 0.8-fm resolution with a fiber laser and 80-nm bandwidth with an external cavity diode laser.The spectroscopic measurements of an ultrahigh Q-factor cavity and gas molecular absorption are experimentally demonstrated.The compact system,predominantly constituted by few-gigahertz electronics and telecommunication components,shows enormous potential for practical spectroscopic applications.

低维纳米材料的理性设计:从结构预测到分子设计

低维纳米材料具有不同于体相材料的物理化学特性,是未来能源、信息与生物等技术的一个重要载体.结构预测与设计作为材料研究与发展的重要内容之一,在低维纳米材料方面的研究具有重要的意义.本文综述了近年来在低维材料理性设计方面的一些研究进展,主要基于全局结构搜索与分子设计,预测具有独特结构与性能的新型低维材料.结合第一性原理电子结构计算方法,针对特定性能开展结构搜索与设计,预测了一系列新型的光催化材料与自旋电子学材料.通过从结构预测到目标设计,可以揭示低维纳米材料中"结构"与"性能"之间的关系,寻找具有特定结构、特殊功能的新型低维纳米材料.

Surface etching induced ultrathin sandwich structure realizing enhanced photocatalytic activity

Photocatalytic conversion efficiency is limited by serious charge carrier recombination. Efficient carrier separation is usually achieved by elegantly-designed multi-component structures connected by directional electric field. Herein, we developed a twodimensional(2 D) sandwich structure, as a new photocatalytic system, to realize high-efficiency carrier separation. This strategy integrated multifunction into a single structure for the first time, which successfully introduces a stable built-in electric field,realizing high-effective carrier separation. Besides, the carrier concentration is dramatically increased due to dimensional confinement. Benefiting from above synergic advantages, 2 D sandwich photocatalyst achieves the highest nitrogen fixation rate(435 μmol g^(-1) h^(-1)) in inorganic solid photocatalysts under visible light irradiation. We anticipate that 2 D sandwich photocatalyst holds promises for the application and expansion of 2 D materials in photocatalysis research.

Review on Speckle-Based Spectrum Analyzer

Accurate spectral measurement and wavelength determination are fundamental and vital for many fields.A compact spectrum analyzer with high performance is expected to meet the growing requirements,and speckle-based spectrum analyzer is a potential solution.The basic principle is based on using the random medium to establish a speckle-to-wavelength mapping relationship for spectrum reconstruction.This article introduces current speckle-based spectrum analyzers with different schemes and reviews recent advances in this field.Besides,some applications by using speckle-based spectrum analyzers are also introduced.Finally,the existing challenges and the future prospects of using speckle for spectrum recovery are discussed.

Data driven discovery of conjugated polyelectrolytes for optoelectronic and photocatalytic applications

Conjugated polyelectrolytes(CPEs),comprised of conjugated backbones and pendant ionic functionalities,are versatile organic materials with diverse applications.However,the myriad of possible molecular structures of CPEs render traditional,trial-and-error materials discovery strategy impractical.Here,we tackle this problem using a data-centric approach by incorporating machine learning with high-throughput first-principles calculations.We systematically examine how key materials properties depend on individual structural components of CPEs and from which the structure–property relationships are established.By means of machine learning,we uncover structural features crucial to the CPE properties,and these features are then used as descriptors in the machine learning to predict the properties of unknown CPEs.Lastly,we discover promising CPEs as hole transport materials in halide perovskite-based optoelectronic devices and as photocatalysts for water splitting.Our work could accelerate the discovery of CPEs for optoelectronic and photocatalytic applications.

High-metallic-phase-concentration MO1-xWxS2 nanosheets with expanded interlayers as efficient electrocatalysts

In most cases, layered transition metal dichalcogenides （LTMDs）, containing metallic phases, show electrochemical behavior different from their semiconductor counterparts. Typically, two-dimensional layered metallic 1T-MoS2 demonstrates better electrocatalytic performance for water splitting compared to its 2H counterpart. However, the characteristics of low metallic phase concentration and poor stability limit its applications in some cases. Herein, we demonstrate a simple and efficient bottom-up wet-chemistry strategy for the large-scale synthesis of nanoscopic ultrathin Mo1-xWxS2 nanosheets with enlarged interlayer spacing and high metallic phase concentration. Our characterizations, including X-ray absorption fine structure spectroscopy （XAFS）, high-angle annular dark-field- scanning transmission electron microscopy （HAADF-STEM）, and X-ray photoelectron spectroscopy （XPS） revealed that the metallic ultrathin ternary Mo1-xWxS2 nanosheets exhibited distorted metal-metal bonds and a tunable metallic phase concentration. As a proof of concept, this optimized catalyst, with the highest metallic phase concentration （greater than 90%）, achieved a low overpotential of about -155 mV at a current density of -10 ma/cm^2, a small Tafel slope of 67 mV/dec, and an increased turnover frequency （TOF） of 1.3 H2 per second at an overpotential of -300 mV （vs. reversible hydrogen electrode （RHE））, highlighting the importance of the metallic phase. More importantly, this study can lead to a facile solvothermal route to prepare stable and high-metallic- phase-concentration transition-metal-based two-dimensional materials for future applications.