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A novel strategy for the synthesis of hierarchical porous carbons (HPCs) from resol by potassium acetate activation for advanced supercapacitor electrodes was reported. The resultant HPCs with a high specific surface area up to 1201 m 2 g −1 as a supercapacitor electrode exhibits a high specific capacitance of 226 F g −1 at 0.05 A g −1 . Besides, the electrode shows high rate capability with 62.4% retention from 0.05 to 20 A g −1 . Moreover, it demonstrates good cyclic stability, showing a high capacitance retention of 97.1% over 5000 charge-discharge cycles at 2.0 A g −1 . The facile, efficient and template-free synthesis strategy for novel 3D-HPCs may promote commercial application of HPCs in the fields of supercapacitors. [ABSTRACT FROM AUTHOR]

• A simple solvent engineering strategy was employed to control morphology of PbI 2 films effectively by water processing. • Platelet-like PbI 2 films can successfully control the residual amount of PbI 2 in perovskite film. • Platelet-like PbI 2 films can control the morphology of the perovskite film and improve the device efficiency [Display omitted] The performance of organic-inorganic perovskite solar cells depends largely on the quality of perovskite film. Currently, various methods are applied to prepare the perovskite film. Among them, the two-step method is counted as a promising candidate to obtain high-quality perovskite film. In this study, we attain a special platelet-like PbI 2 films by applying pure water to cover wet PbI 2 film and standing for a period of time. The unique morphology contributes to the entry of organic cations solution into the PbI 2 and promoting its reaction with PbI 2 , which reducing the residual amount of PbI 2 in the perovskite film. Compared to the traditional two-step method, water processing method can obtain a high-quality perovskite film with enlarged grain size, improved crystallization, and prolonged carrier lifetime. As a result, the efficiency of the prepared device based on the film has increased from 17.90% without water processing to 20.14% of water processing. Which demonstrates that this solvent engineering for PbI 2 film opens up a possibility to prepare high-quality perovskite in a two-step method and obtain highly efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]

Overcoming the self-corrosion and surface passivation of aluminum anode, and the slow kinetics of cathodic electrochemical reactions are of great significance for the practical application of aluminum–air battery. In this study, we replaced the traditional aqueous electrolyte with AlCl 3 -urea ionic liquid electrolyte, and prepared Co–MnO 2 /C catalysts as cathode catalyst. Structures and electrocatalytic activity of the x % Co–MnO 2 /C (x is the mole percent of Co to Mn, x = 0, 10, 20, 30, 40 and 50) catalysts have been investigated systematically. After Co ions intercalation, the specific surface area of the catalyst increased and average pore diameter decreased. The unique interaction between Co ions and MnO 2 led to an increase in the catalytic activity of the catalyst in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) compared with MnO 2 /C. In particular, 40% Co–MnO 2 /C showed the largest specific surface area (154.25 m2 g−1) and the smallest average pore diameter (6.47 nm). It showed the most positive half-wave potential (0.727 V vs. RHE) and the biggest limiting current density (4.744 mA cm−2) in ORR process, and also exhibited the lowest onset potential (1.593 V) and the biggest limit current density (15.177 mA cm−2) in OER process. Furthermore, aluminum–air battery assembled with 40% Co–MnO 2 /C demonstrated excellent reversible charge and discharge performance, which had an average discharge voltage of 1.5 V and an average charge voltage of 2 V during 30 cycles at a limited battery capacity of 375 mAh g−1. Our results reveal the possibility of designing a rechargeable aluminum-air battery working at ambient conditions based on the Co–MnO 2 /C air cathode catalyst for the first time. Our work opens up a new way to achieve the rechargeability of aluminum-air batteries, and our highly active electrocatalytic materials can be used in a wider range of electrochemical energy applications. Co–MnO 2 /C catalysts were prepared by intercalating Co ions between MnO 2 layers, the unique interaction between Co ions and MnO 2 led to an increase in the catalytic activity of the catalysts in ORR/OER process compared with MnO 2 /C, and the aluminum–air battery assembled with 40% Co–MnO 2 /C catalyst and AlCl 3 -urea ionic liquid electrolyte demonstrated excellent reversible charge and discharge performance. Image 1 • A novel Co–MnO 2 /C catalyst was successfully prepared by intercalating Co ions between MnO 2 layers. • The unique interaction between Co ions and MnO 2 led to an increase in the catalytic activity of the catalyst. • 40% Co–MnO 2 /C as air cathode catalyst exhibited the best ORR/OER catalytic activity. • A button-type rechargeable aluminum-air battery working at ambient conditions was designed for the first time. • As-prepared aluminum-air battery demonstrated excellent reversible charge and discharge performance. [ABSTRACT FROM AUTHOR]

Gas-quenching fabrication of perovskite films demonstrates promising compatibility for commercialization of perovskite photovoltaics. Seeking suitable ligand for the perovskite precursor inks to improve the crystalline quality of gas-quenched methylammonium free perovskite films is critical for realizing up-scalable fabrication of stable perovskite solar cells. In this work, a series of pyrrolidone-based ligands are employed in gas-quenching fabrication of FA 0.9 Cs 0.1 PbI 3 perovskite films. Optical and morphological characterizations indicate 2-pyrrolidone is the most preferred ligand to deliver a neat buried-interface as well as a light-trapping surface at the rear of the device, which maximized the light-harvesting and the photocurrent of the device. The corresponding device achieved a power conversion efficiency of 21.6% without any interfacial passivation, as well as reduced defect density from their electrical characteristics. Moreover, a more stable performance of the device is obtained with 2-pyrrolidone compared to other pyrrolidone-based ligands, demonstrating 2-pyrrolidone as a promising ligand in designing the perovskite inks for methylammonium-free perovskite solar cells. • Various pyrrolidone-based ligands are studied in gas-quenching of FA 0.9 Cs 0.1 PbI 3 films. • Bifacial optical properties of perovskite films are optimized with NP ligand. • smoother buried interface and a rougher surface contribute to enhanced light harvesting. • NP device achieved 21.6% efficiency without any interfacial passivation [ABSTRACT FROM AUTHOR]

Lead halide perovskite solar cells (PSCs) have attracted intensive attention since their power conversion efficiency (PCE) increased sharply in recent years. Thereinto, triple cation perovskite (TCP) is a popular light absorption layer for PSCs due to its excellent thermal and humidity stability. However, a large amount of MA+ (≥15%) and Br- (≥15%) in TCP makes the bandgap widen drifting from the optimum value. There is some extent of a trade-off between PCE and stability for PSCs, and narrow-bandgap TCP is one of the best choices for light absorption material to achieve an optimum balance between PCE and stability. Herein, we prepared a narrow-bandgap (1.56 eV) high-quality TCP (Cs 0.05 FA 0.86 MA 0.09 Pb(I 0.97 Br 0.03) 3) film with an average grain size up to 1208 nm and corresponding PSC with high efficiency of 20.8%. Moreover, the intermediate process of the TCP film crystallization was carefully studied disclosing the critical α-Phase intermediate and corresponding roles of DMSO solvent and MACl additive through quasi-in-situ XRD in the film formation process, and the results may give critical clues to the fabrication of high-quality narrow-bandgap TCP based PSCs. • High-quality FAPbI3-based TCP film with a narrow-bandgap (1.56 eV) was successfully prepared by applying the α-phase intermediate strategy: the grain size of the film can reach 1208 nm and the carrier lifetime exceeds 3 μs. • The crytical intermediate process introduced by the synergy of DMSO and MACl was disclosed through quasi-in-situ XRD in the film formation process. • The solar cells based on the low-doping FAPbI 3 -based TCP films show high performance and good stability even without surface passivation. [ABSTRACT FROM AUTHOR]

Graphene is considered as a promising electrode material for supercapacitors due to its large specific surface area, excellent electrical conductivity and so on. In this paper, few-layer graphene is prepared by self-propagating combustion reaction between CO and metal magnesium, using powder MgO as deposition template. Graphene with a high specific surface area of up to 928 m2 g−1 replicates the morphological feature of powder MgO. Raman spectroscopy analysis demonstrates that the graphene layer decreases when the dosage of MgO template is increased. The specific capacitance of as-prepared sample exhibits the highest specific capacitance of 222 F g−1 at the current density of 1 A g−1 in EMI [TFSI] electrolyte. The sample demonstrates a "double high" performance with high specific energy density and high specific power density. A high energy density of 76.3 Wh kg−1 can be achieved at a specific power density of 1.75 kW kg−1, and it can still remain 48.6 Wh kg−1 when the specific power density reaches a high level of 35 kW kg−1. • Self-propagating combustion reaction synthesis graphene. • Synthesis graphene from CO and Mg. • Synthesized graphene has good structural properties. • Excellent capacitive performances in the electrolyte of EMI [TFSI]. [ABSTRACT FROM AUTHOR]