Energy

Vibrations with various frequencies in daily life and industry can cause health hazards and fatigue failure of critical structures, which requires the development of elastomers with high energy dissipation at desired frequencies. Current strategies relying on tuning characteristic relaxation time of polymer chains are mostly qualitative empirical methods, and it is difficult to precisely control damping performances. Here, we report a general strategy for constructing dynamic crosslinked polymer fluid gels that provide controllable ultrahigh energy dissipation. This is realized by dynamic-bond-mediated chain reptation of polymer fluids in a crosslinked network, where the characteristic time of chain reptation is dominated by the presence of well-defined dissociation time of dynamic bonds and almost independent of their molar mass. Using prototypical supramolecular polydimethylsiloxane elastomers, we demonstrate that dynamic crosslinked polymer fluid gels exhibit a controllable ultrahigh damping performance at desired frequencies (10^-2 ~ 10^2 Hz), exceeding that of typical state-of-the-art silicone damping materials. Their shock absorption is over 300% higher than that of commercial silicone rubber under the same impact force.

Published in: "Angewandte Chemie International Edition".

Magnesium batteries attract interest as alternative energy-storage devices because of elemental abundance and potential for high energy density. Development is limited by the absence of suitable cathodes, associated with poor diffusion kinetics resulting from strong interactions between Mg2+ and the host structure. V2PS10 is reported as a positive electrode material for rechargeable magnesium batteries. Cyclable capacity of 100 mAh g-1 is achieved with fast Mg2+ diffusion of 7.2[[EQUATION]]10-11-4[[EQUATION]]10-14 cm2s-1. The fast insertion mechanism results from combined cationic redox on the V site and anionic redox on the (S2)2- site; enabled by reversible cleavage of S–S bonds, identified by X-ray photoelectron and X-ray absorption spectroscopy. Detailed structural characterisation with maximum entropy method analysis, supported by density functional theory calculations and projected density of states analysis, reveals that the sulphur species involved in anion redox are not connected to the transition metal centres, spatially separating the two redox processes. This facilitates fast and reversible Mg insertion in which the nature of the redox process depends on the cation insertion site, creating a synergy between the occupancy of specific Mg sites and the location of the electrons transferred.

Published in: "Angewandte Chemie International Edition".

A facile approach to reduce the crystallinity difference between donor and acceptor has been proposed by incorporating a novel liquid crystal small molecule, BDTPF4-C6, which balances charge transport and suppresses charge recombination in organic solar cells. Intriguingly, dual Förster resonance energy transfer was firstly observed between guest molecule and host donor and acceptor, resulting in increased charge generation in ternary blend. Abstract Achieving a more balanced charge transport by morphological control is crucial in reducing bimolecular and trap-assisted recombination and enhancing the critical parameters for efficient organic solar cells (OSCs). Hence, a facile strategy is proposed to reduce the crystallinity difference between donor and acceptor by incorporating a novel multifunctional liquid crystal small molecule (LCSM) BDTPF4-C6 into the binary blend. BDTPF4-C6 is the first LCSM based on a tetrafluorobenzene unit and features a low liquid crystal phase transition temperature and strong self-assembly ability, conducive to regulating the active layer morphology. When BDTPF4-C6 is introduced as a guest molecule into the PM6 : Y6 binary, it exhibits better compatibility with the donor PM6 and primarily resides within the PM6 phase because of the similarity-intermiscibility principle. Moreover, systematic studies revealed that BDTPF4-C6 could be used as a seeding agent for PM6 to enhance its crystallinity, thereby forming a more balanced and favourable charge transport with suppressed charge recombination. Intriguingly, dual Förster resonance energy transfer was observed between the guest molecule and the host donor and acceptor, resulting in an improved current density. This study demonstrates a facile approach to balance the charge mobilities

Published in: "Angewandte Chemie International Edition".

The incorporation of pentagon–heptagon pairs into helical nanographenes lacks a facile synthetic route, and the impact of these pairs on chiroptical properties remains unclear. In this study, a method for the stepwise construction of pentagon–heptagon pairs in helical nanographenes by the dehydrogenation of [6]helicene units was developed. Three helical nanographenes containing pentagon–heptagon pairs were synthesized and characterized using this approach. A wide variation in the molecular geometries and photophysical properties of these helical nanographenes was observed, with changes in the helical length of these structures and the introduction of the pentagon–heptagon pairs. The embedded pentagon–heptagon pairs reduced the oxidation potential of the synthesized helical nanographenes. The high isomerization energy barriers enabled the chiral resolution of the helicene enantiomers. Chiroptical investigations revealed remarkably enhanced circularly polarized luminescence and luminescence dissymmetry factors with an increasing number of the pentagon–heptagon pairs.

Published in: "Angewandte Chemie International Edition".

A new porphyrin conjugated polymer cathode, COP500-CuT2TP is achieved under electrochemical polymerization. Self-exfoliation of polymer cathode promotes charge storage, leading to a specific capacity of 420 mAh g−1 and 900 Wh Kg−1. Excellent cycling stability up to 8000 cycles at 5 A g−1 is achieved. Mechanistic insights by combining experimental and computational investigations supports the charge storage performance. Abstract Organic electrode materials are promising for next-generation energy storage materials due to their environmental friendliness and sustainable renewability. However, problems such as their high solubility in electrolytes and low intrinsic conductivity have always plagued their further application. Polymerization to form conjugated organic polymers can not only inhibit the dissolution of organic electrodes in the electrolyte, but also enhance the intrinsic conductivity of organic molecules. Herein, we synthesized a new conjugated organic polymer (COPs) COP500-CuT2TP (poly [5,10,15,20-tetra(2,2′-bithiophen-5-yl) porphyrinato] copper (II)) by electrochemical polymerization method. Due to the self-exfoliation behavior, the porphyrin cathode exhibited a reversible discharge capacity of 420 mAh g−1, and a high specific energy of 900 Wh Kg−1 with a first coulombic efficiency of 96 % at 100 mA g−1. Excellent cycling stability up to 8000 cycles without capacity loss was achieved even at a high current density of 5 A g−1. This highly conjugated structure promotes COP500-CuT2TP combined high energy density, high power density, and good cycling stability, which would open new opportunity for the designable and versatile organic electrodes for electrochemical energy storage.

Published in: "Angewandte Chemie International Edition".

CsPbI3 perovskite receives tremendous attention for photovoltaic applications due to its ideal bandgap and good thermal stability. However, CsPbI3 perovskite solar cells (PSCs) significantly suffer from photovoltage deficits because of serious interfacial energy losses within the PSCs, which to a large extent affects the photovoltaic performance of PSCs. Herein, a dipolar chemical bridge (DCB) is constructed between the perovskite and TiO2 layers to lower interfacial energy losses and thus improve the charge extraction of PSCs. The results reveal that the DCB could form a beneficial interfacial dipole between the perovskite and TiO2 layers, which could optimize the interfacial energetics of perovskite/TiO2 layers and thus improve the energy level alignment within the PSCs. Meanwhile, the constructed DCB could also simultaneously passivate the surface defects of perovskite and TiO2 layers, greatly lowering interfacial recombination. Consequently, the photovoltage deficit of PSCs is largely reduced, leading to a record efficiency of 21.86% being realized. Meanwhile, the operation stability of PSCs is also largely improved due to the high-quality perovskite films with released interfacial tensile strain being obtained after forming the DCB within the PSCs.

Published in: "Angewandte Chemie International Edition".

Tin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn2+, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. After adding 3-aminopyrrolidine dihydro iodate (APDI2) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI2 could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In-situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI2. The resulting film with APDI2 shows a pinhole-free morphology with fewer defects, achieving an impressive efficiency of 15.13%.

Published in: "Angewandte Chemie International Edition".

This Scientific Perspective outlines best practice in the design of plasma catalysis experiments. A water pumping model depicts the limitations of an exergonic reaction that surpasses thermodynamic equilibrium, where the pump represents the plasma. The leak back causes energy dissipation, depending on the water level in the upper reservoir (representing conversion) and the size of the leak (representing plasma activation of the product). Abstract Best practices in testing heterogeneous catalysts are translated to plasma-catalytic experiments. Independent determination of plasma-catalytic and plasma-chemical contributions is essential. Non-porous catalyst particles are preferred because active sites inside sub-micron pores cannot contribute. Temperature variation is needed to determine kinetics, despite the complexity of thermal effects in plasma. Rigorous checks on catalyst deactivation and mass balance are needed. Plasma enhanced reversed reactions should be minimized by keeping conversion low and far from thermodynamic equilibrium, preventing underestimation of the rate of forward reaction. In contrast, plasma-catalytic studies often aim at conversions surpassing thermodynamic equilibrium, not obtaining any information on kinetics. Calculation of catalyst activity per active sites (turn-over-frequency) requires also appropriate characterization to determine the number of active sites. The relationship between kinetics and thermodynamics for plasma-catalysis is discussed using endothermic decomposition of CO2 and exothermic synthesis of ammonia from N2 and H2 as examples. Assuming Langmuir–Hinshelwood and Eley-Rideal mechanisms, the effect of excitation of reactant molecules on activation barriers and surface coverages are discussed, influencing reaction rates. The consequences of reversed reactions are considered. Plasma-catalysis with catalysts applied for thermal catalysis at much higher temperature

Published in: "Angewandte Chemie International Edition".

Heterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric-to-paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two-dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric-to-paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro-catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption.

Published in: "Angewandte Chemie International Edition".

Inorganic perovskite solar cells (IPSCs) have gained significant attention due to their excellent thermal stability and suitable bandgap (~1.7 eV) for tandem solar cell applications. However, the defect-induced non-radiative recombination losses, low charge extraction efficiency, energy level mismatches, and so on render the fabrication of high-efficiency inverted IPSCs remains challenging. Here, the use of 3-amino-5-bromopyridine-2-formamide (ABF) in methanol was dynamically spin-coated on the surface of CsPbI2.85Br0.15 film, which facilitates the limited etching of defect-rich subsurface layer, resulting in the formation of vertical PbI2 nanosheet structures. This enabled localized contacts between the perovskite film and the electron transport layer, suppress the recombination of electron-hole and beneficial to electron extraction. Additionally, the C=O and C=N groups in ABF effectively passivated the undercoordinated Pb2+ at grain boundaries and on the surface of CsPbI2.85Br0.15 film. Eventually, we achieved a champion efficiency of 20.80% (certified efficiency of 20.02%) for inverted IPSCs with enhanced stability, which is the highest value ever reported to date. Furthermore, we successfully prepared p-i-n type monolithic inorganic perovskite/silicon tandem solar cells　(IPSTSCs) with an efficiency of 26.26%. This strategy provided both fast extraction and efficient passivation at the electron-selective interface.

Published in: "Angewandte Chemie International Edition".