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Single-atom catalysts (SACs) have exhibited exceptional atomic efficiency and catalytic performance in various reactions but suffer poor stability. Understanding the structure–stability relation is the prerequisite for stability optimization but has been rarely explored due to complexity of the degradation process and reaction environments. Herein, we successfully established the structure–stability relation of N-doped carbon-supports SACs (MN4SACs) under working conditions of CO2reduction, by using advanced constant-potential density functional theory calculations. Systematic mechanism investigation that considered different factors identifies the key role of initial hydrogen adsorption on the coordination N atom in catalytic stability, where the feasibility of the adsorption eventually determines the leaching of the metal atom. On this basis, a simple descriptor consisting of electron number and electronegativity is constructed, realizing accurate and rapid prediction of the stability of SACs. Furthermore, strategies via modifying the local geometric structure to improve the stability without changing the active centers are proposed accordingly, which are supported by related experiments. These findings fill the current void in understanding SAC stability under practical working conditions, potentially advancing the widespread application of SACs in sustainable energy conversion systems.

The performance of supported catalysts is largely decided by metal–support interactions, which is of great significance for the rational design of catalysts. However, how to quantify the structure–activity relationship of supported catalysts remains a great challenge. In this work, taking MoS2and WS2supported single atom catalysts (SACs) as prototypes, a simple descriptor, namely, effective d electron number (labeled as Φ), is constructed to quantitatively describe the effect of metal–support interaction on the nitrogen reduction reaction (NRR) activity. This descriptor merely consists of intrinsic properties of the catalyst (including the number of d electrons, electronegativity of the metal atoms and generalized electronegativity of the substrate atoms) and can accurately predict the limiting potential (UL) for the NRR, with no need for any density functional theory calculations. Moreover, this descriptor possesses superb expansibility that can be applied to other materials, including other metal dichalcogenide (MoSe2, MoTe2, WSe2, WTe2and NbS2) and even MXene (V2CO2, Ti2CO2and Nb2CO2)-supported SACs. On this basis, a fast screening of excellent NRR catalysts among these systems is performed and three promising NRR catalysts (i.e.Mo@WTe2, Mo@V2CO2and Re@NbS2) are successfully selected with ULas low as −0.32, −0.24 and −0.31 V, respectively. This work offers new opportunities for advancing the rapid discovery of high-efficiency NRR catalysts, and the design principle is expected to be widely applicable to other catalytic systems and beyond.

Preparation of regioisomerically pure 1,6-disubstituted perylene diimide (PDI) is not a trivial task owing to the lack of facile synthetic and separation methodologies for the precursors. Herein, we present a simple synthesis for 1,6-ditriflato-PDI (1,6-diOTf-PDI) using 1,6,9,10-tetrabromo-perylene monoimide 1as the starting material. The selective methoxylation of 1at the 1,6-position is the key step. Based on a four-step sequence of selective methoxylation, domino carbonylative amidation, demethylation, and triflation, 1,6-diOTf-PDIcan be obtained in a satisfactory yield. Moreover, as a building block, 1,6-diOTf-PDIacan readily undergo Suzuki and Sonogashira cross-coupling reactions.

The random distribution of graphene in epoxy matrix hinders the further applications of graphene-epoxy composites in the field of tribology. Hence, in order to fully utilize the anisotropic properties of graphene, highly aligned graphene-epoxy composites (AGEC) with horizontally oriented structure have been fabricated via an improved vacuum filtration freeze-drying method. The frictional tests results indicated that the wear rate of AGEC slowly increased from 5.19×10−6mm3/(N·m) to 2.87×10−5mm3/(N·m) with the increasing of the normal load from 2 to 10 N, whereas the friction coefficient (COF) remained a constant of 0.109. Compared to the neat epoxy and random graphene-epoxy composites (RGEC), the COF of AGEC was reduced by 87.5% and 71.2%, and the reduction of wear rate was 86.6% and 85.4% at most, respectively. Scanning electron microscope (SEM) observations illustrated that a compact graphene self-lubricant film was formed on the worn surface of AGEC, which enables AGEC to possess excellent tribological performance. Finally, in light of the excellent tribological properties of AGEC, this study highlights a pathway to expand the tribological applications of graphene-epoxy composites.

An electric-drive circular-cutting and middle-placing windrower for oilseed rape is designed. Circular cutter adopts the cutting method that a chain-driven movable blade is combined with upper and lower double fixed blades, and designs a double-support circular cutter as well. Moreover, the symmetrical hugging and middle-placing reeling device is designed through artificial reeling operation. The simulated and kinematic analysis of the reeling device is done as well. The simulated analysis results show that the reeling track meets the operation requirement and the reeling devices have a good effect on the rape plants. The intelligent synchronous reeling control is designed on the reeling device drive. The field test of the prototype showed that the placing angle of the windrower was 11.48°, and the angle difference was 6.64°.This research provides theoretical and technical references for the design of the circular-cutting and middle-placing windrower for oilseed rape.

Organic redox-active molecules have been identified as promising cathodes for practical usage of potassium-ion batteries (PIBs) but still struggle with serious dissolution problems and sluggish kinetic properties. Herein, we propose a pseudocapacitance-dominated novel insoluble carbonyl-based cathode, [2,6-di[1-(perylene-3,4,9,10-tetracarboxydiimide)]anthraquinone, AQ–diPTCDI], which possesses high reversible capacities of 150 mAh g–1, excellent cycle stability with capacity retention of 88% over 2000 cycles, and fast kinetic properties. The strong intermolecular interactions of AQ–diPTCDI and in situformed cathode electrolyte interphase films support it against the dissolution problem. The high capacitive-like contribution in capacities and fast potassium-ion diffusion enhance its reaction kinetics. Moreover, a symmetric organic potassium-ion battery (OPIB) based on AQ–diPTCDI electrodes also exhibits outstanding K-storage capability. These results suggest that AQ–diPTCDI is a promising organic cathode for OPIBs and provide a practicable route to realize high-performance K storage.

In order to realise high-efficiency hole-forming and pursue optimal forming hole parameters which satisfied agricultural requirements for awl-shaped punch transplanter, a optimally designed indigenously-developed pure rolling planting hole-forming machine's hole forming mechanism parts is proposed. The CAD software graphing method was used to study the effect of forming planting hole by structural parameters, with the numerical simulation method by MATLAB 7.0 software and CATIA software were used to verify the rationality of the hole-forming key parameters optimisation design. Subsequently, prototype trial-production was carried out, followed by field testing. The results showed that forming planting hole opening lengthwise shrank from originally 88.8 mm to 72.6 mm, lateral width was 41.2 mm, the effective depth reduced from 58.9 mm to 48.5 mm, qualified radio of forming planting hole reached to 95.1%, which 1.93% higher than the original prototype, which was significant for the provision of technical support for the design of new transplanter.

Perylene diimide (PDI) and the vinylene-bridged helical PDI oligomers are versatile building blocks for constructing nonfullerene acceptors (NFAs). In this contribution, a benzene-cored star-shaped NFA, namely, TPDI2-Se, was designed and synthesized for organic solar cells (OSCs). The NFA with smaller π-conjugated blades, namely, TPDI-Se, was synthesized for comparison. Using the commercially available PTB7-Th as the electron donor, the best power conversion efficiency (PCE) of 3.62% was obtained for TPDI-Se-based OSCs. However, a much higher PCE of 8.59% was achieved for TPDI2-Se-based devices owing to the π-extension in the peripheral panels. Moreover, the photovoltaic performance of TPDI2-Se-based OSCs is also superior to those of the parent NFA TPDI2 (PCE of 7.84%)- and the blade moiety PDI2-Se (PCE of 6.61%)- based ones. Additionally, a remarkable short-circuit current (Jsc) value of 17.21 mA/cm2was obtained for TPDI2-Se-based OSCs, which is among the highest Jscvalues reported in PDI-based OSCs. These results argue that the so-called “three in one” molecule design strategy of π-extension, selenium incorporation, and trimerization offers a robust approach to constructing high-performance PDI-based NFAs.

Two star-shaped helical perylene diimide (PDI) electron acceptors TPDI2 and FTPDI2 were designed and synthesized for nonfullerene organic solar cells (OSCs). The integration of helical PDIs into a three-dimensional structure provides a new strategy to tune the intermolecular interactions, and the as-cast blend films with PTB7-Th show favorable morphology as well as efficient charge transfer and separation, as evidenced by the morphology and femtosecond transient absorption (fs-TA) spectroscopy studies. A trade-off between suppressing the self-aggregation and maintaining the charge-transfer properties was achieved by FTPDI2. Using PTB7-Th as the electron donor, the FTPDI2-based nonfullerene OSCs show a high power conversion efficiency of 8.28%, without the assistance of any additives.