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Perovskite solar cells (PSCs) have reached certified efficiencies of up to 23.7% but suffered from frailness and instability when exposed to ambient atmosphere. Zinc oxide (ZnO), when used as electron transport layer (ETL) on PSCs, gives rise to excellent electronic, optic, and photonic properties, yet the Lewis basic nature of ZnO surface leads to deprotonation of the perovskite layer, resulting in serious degradation of PSCs using ZnO as ETL. Here, we report a simple but effective strategy to convert ZnO surface into ZnS at the ZnO/perovskite interface by sulfidation. The sulfide on ZnO–ZnS surface binds strongly with Pb2+ and creates a novel pathway of electron transport to accelerate electron transfer and reduce interfacial charge recombination, yielding a champion efficiency of 20.7% with improved stability and no appreciable hysteresis. The model devices modified with sulfide maintained 88% of their initial performance for 1000 h under storage condition and 87% for 500 h under UV radiation. ZnS is d...

Electrochemical conversion of CO2 into fuels using electricity generated from renewable sources helps to create an artificial carbon cycle. However, the low efficiency and poor stability hinder the practical use of most conventional electrocatalysts. In this work, a 2D hierarchical Pd/SnO2 structure, ultrathin Pd nanosheets partially capped by SnO2 nanoparticles, is designed to enable multi-electron transfer for selective electroreduction of CO2 into CH3 OH. Such a structure design not only enhances the adsorption of CO2 on SnO2 , but also weakens the binding strength of CO on Pd due to the as-built Pd-O-Sn interfaces, which is demonstrated to be critical to improve the electrocatalytic selectivity and stability of Pd catalysts. This work provides a new strategy to improve electrochemical performance of metal-based catalysts by creating metal oxide interfaces for selective electroreduction of CO2 .

The development of portable and wearable electronic devices has substantially increased the demand for printed circuit boards with high thermal conductivity, optimal mechanical flexibility, electrical insulativity, and minimal high-frequency transmission loss. Herein, we demonstrate the fabrication of a thermally conductive, flexible composite paper, for electronic and microwave devices, based on hexagonal boron nitride nanosheets, poly(vinyl alcohol) (PVA), and fiberglass mesh (FGM). The prepared composite paper exhibits in-plane thermal conductivity of 22.51 W/(m·K), and the FGM induced high mechanical strength of 27.92 MPa. The transmission loss, of the grounded coplanar waveguide lines, was 0.10 dB/mm at 7.0 GHz, and shows negligible variation while bending, indicating the high flexibility of the circuit board. These results demonstrate potential application of BN-based composite paper in flexible electronic devices.

Summary Lithium-sulfur (Li-S) batteries are a promising next-generation energy-storage system due to their high theoretical energy density and low cost. However, the rapid capacity fading of high-sulfur-loading cathodes caused by the shuttle of soluble polysulfide intermediates between two electrodes heavily hinders the development of high-energy-density Li-S batteries. We develop in this work a powerful functional separator to suppress the polysulfide shuttle by coating two-dimensional nitrogen-doped porous carbon nanosheets on one surface of a commercial polypropylene separator. The high surface area, high content of nitrogen dopants, and close-packing laminar structure of the two-dimensional porous carbon nanosheets make them ideal to fabricate a lightweight and thin separator for high-energy-density Li-S batteries. The separator reported in this work endows the high-sulfur-loading cathodes made of commercial carbon materials with significantly enhanced performances that are comparable with or even superior to the state-of-the-art sulfur composite cathodes, opening up new opportunities for designing practical high-energy-density Li-S batteries.

Transition-metal chalcogenides have attracted great attention for their superior catalytic activity towards hydrogen evolution reaction (HER) as an alternative to platinum. Here we report a facile method for synthesizing two-dimensional nickel disulfide (NiS 2 ) by using Ni(OH) 2 on nickel foam as substrate. The as-synthesized NiS 2 displayed an activation period during HER with a remarkable structural and compositional change under alkaline conditions. Electrochemical in situ X-ray absorption spectroscopy revealed that metallic Ni acted as catalytic active species with superior activity of 67 mV to reach 10 mA cm −2 . The in situ generated metallic Ni were easily oxidized to large-area ultrathin Ni(OH) 2 when exposed to air. The overall water splitting device was fabricated by using NiS 2 -derived metallic Ni and Fe doped NiS 2 -derived hydroxide as HER and OER electrode with a potential of 1.52 V to reach 10 mA cm −2 .

Summary Two-dimensional (2D) nanosheets (NSs) of a Ni-S coordination polymer have been successfully synthesized with the use of 2D Ni(OH) 2 NSs grown on conductive carbon cloth as the template and 1,4-benzenedithiol as the ligand. In situ X-ray absorption spectroscopy revealed that the as-prepared catalyst was entirely transformed into ultrathin Ni NSs under alkaline reductive conditions. The in-situ-generated catalysts exhibited superior activity toward the hydrogen evolution reaction (HER) with an overpotential of 80 mV to reach 10 mA cm −2 . Studies revealed that the large-area ultrathin Ni NSs served as active sites for H 2 generation, and the trace sulfur adsorbed on the Ni surface promoted water dissociation. This work has developed a templating approach for preparing highly active HER electrocatalysts and identified the real active sites under electrocatalytic conditions.

An effective strategy is developed to synthesize high-nuclearity Cu clusters, [Cu53 (RCOO)10 (C≡CtBu)20 Cl2 H18 ]+ (Cu53 ), which is the largest CuI /Cu0 cluster reported to date. Cu powder and Ph2 SiH2 are employed as the reducing agents in the synthesis. As revealed by single-crystal diffraction, Cu53 is arranged as a four-concentric-shell Cu3 @Cu10 Cl2 @Cu20 @Cu20 structure, possessing an atomic arrangement of concentric M12 icosahedral and M20 dodecahedral shells which popularly occurs in Au/Ag nanoclusters. Surprisingly, Cu53 can be dissolved in diethyl ether and spin coated to form uniform nanoclusters film on organolead halide perovskite. The cluster film can subsequently be converted into high-quality CuI film via in situ iodination at room temperature. The as-fabricated CuI film is an excellent hole-transport layer for fabricating highly stable CuI-based perovskite solar cells (PSCs) with 14.3 % of efficiency.

An effective strategy is developed to synthesize high-nuclearity Cu clusters, [Cu

Electrochemical conversion of CO

Air-stable atomically thick copper nanosheets are prepared and used for selective electrochemical reduction of CO2 into CO., The electrochemical conversion of CO2 and H2O into syngas using renewably generated electricity is an attractive approach to simultaneously achieve chemical fixation of CO2 and storage of renewable energy. Developing cost-effective catalysts for selective electroreduction of CO2 into CO is essential to the practical applications of the approach. We report a simple synthetic strategy for the preparation of ultrathin Cu/Ni(OH)2 nanosheets as an excellent cost-effective catalyst for the electrochemical conversion of CO2 and H2O into tunable syngas under low overpotentials. These hybrid nanosheets with Cu(0)-enriched surface behave like noble metal nanocatalysts in both air stability and catalysis. Uniquely, Cu(0) within the nanosheets is stable against air oxidation for months because of the presence of formate on their surface. With the presence of atomically thick ultrastable Cu nanosheets, the hybrid Cu/Ni(OH)2 nanosheets display both excellent activity and selectivity in the electroreduction of CO2 to CO. At a low overpotential of 0.39 V, the nanosheets provide a current density of 4.3 mA/cm2 with a CO faradaic efficiency of 92%. No decay in the current is observed for more than 22 hours. The catalysts developed in this work are promising for building low-cost CO2 electrolyzers to produce CO.

How to exert the energy density advantage is a key link in the development of lithium–sulfur batteries. Therefore, the performance degradation of high-sulfur-loading cathodes becomes an urgent problem to be solved at present. In addition, the volumetric capacities of high-sulfur-loading cathodes are still at a low level compared with their areal capacities. Aiming at these issues, two-dimensional carbon yolk-shell nanosheet is developed herein to construct a novel self-supporting sulfur cathode. The cathode with high-sulfur loading of 5 mg cm−2 and sulfur content of 73 wt% not only delivers an excellent rate performance and cycling stability, but also provides a favorable balance between the areal (5.7 mAh cm–2) and volumetric (1330 mAh cm–3) capacities. Remarkably, an areal capacity of 11.4 mAh cm–2 can be further achieved by increasing the sulfur loading from 5 to 10 mg cm–2. This work provides a promising direction for high-energy-density lithium–sulfur batteries., One of the challenges facing lithium-sulfur batteries is to develop cathodes with high mass and high volume loading. Here the authors show that two-dimensional carbon yolk-shell nanosheets are promising sulfur host materials, enabling stable battery cells with high energy density.