The photoactive alpha-phase perovskite plays a pivotal role in determining the efficiency and stability of perovskite solar cells (PSCs). Herein, we propose an innovative strategy for seed-assisted epitaxial growth based on latticematching. The pre-synthesized (GABA)2PbI4 single crystals as seeds are introduced into the three-dimensional (3D) perovskite precursor solution, successfully achieved the preferential and rapid formation of the photoactive alpha-phase at room temperature. In situ grazing-incidence wide-angle X-ray scattering (GIWAXS) reveals the seed-induced accelerated crystallization process of the alpha-phase perovskite. The highly matched lattice constants between the seeds and alpha-FAPbI3, the reduced nucleation barrier, and the suppressed delta-phase are analyzed to be the primary factors, ultimately resulting in the formation of vertically oriented, gradient-distributed perovskite films. Finally, FACs-based perovskite devices fabricated by using this method achieved a high efficiency of 24.15% and excellent stability, retaining over 90% of their initial efficiency after 900 h.

Additives are one of the important means to improve the performance of perovskite solar cells. To explore the effects of different addition methods on the crystallinity of perovskite, in this paper, guanidine thiocyanate (GASCN) is added in three different methods, i.e., added in SnO 2 precursor solution; in PbI 2 precursor solution; or FAI precursor solution, respectively. The guanidine hydroiodide (GAI) and methylamine thiocyanate (MASCN) are selected as contrast additives to evaluate the role of GA + and SCN − . Though the efficiency and stability of the perovskite solar cells with all additives are improved, the systematic study by grazing incidence wide‐angle X‐ray scattering (GIWAXS), quasi‐in situ GIWAXS, and in situ X‐ray diffraction (XRD) proved that the mechanism by the three different addition methods behaved in many different ways, which corresponded, respectively, to the surface of the SnO 2 electron transport layer, dominance orientation especially vertical growth of perovskite, or low‐dimensional perovskite structure. This provides a new view for optimizing the appropriate synthesis conditions in the future.

Quasi-2D perovskites show great potential as photovoltaic devices with superior stability, but the power conversion efficiency (PCE) is limited by poor carrier transport. Here, it is simultaneously affected the hole transport layer (HTL) and the perovskite layer by incorporating pyridine-based materials into poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) to address the key problem above in 2D perovskites. With this approach, the enhanced optoelectronic performance of the novel PEDOT:PSS is due to electron transfer between the additives and PEDOT or PSS, as well as a dissociation between PEDOT and PSS based on experimental and theoretical studies, which facilitates the charge extraction and transfer. Concurrently, in-situ X-ray scattering studies reveal that the introduction of pyridine-based molecules alters the transformation process of the perovskite intermediate phase, which leads to a preferred orientation and ordered distribution caused by the Pb─N chemical bridge, achieving efficient charge transport. As a result, the pyridine-treated devices achieve an increased short-circuit current density (Jsc) and PCE of over 17%.

New binary carbon composites (GDY-NCNTs and GDY-CNTs) with a three-dimensional porous structure, which are synthesized by an in situ growth method, are adopted in this article. The GDY-NCNTs composites exhibit excellent specific capacitance performance (679 F g(-1), 2 mV s(-1), 139% increase compared to GDY-CNTs) and good cycling stability (with a capacity retention rate of up to 116% after 10000 cycles). The three-dimensional porous structure not only promotes ion transfer and increases the effective specific surface area to improve its specific capacitance performance but also adapts to the volume expansion and contraction during the charging and discharging process to improve its cycling stability. The presence of nitrogen doping in the carbon nanotubes of GDY-NCNTs increases the surface defects of the composites, provides more electrochemical points, and improves the surface wettability of the composites, further improving the electrochemical performance of the composites.

The buried interface of perovskite plays a crucial role in attaining superior performance, partly due to its influence on the structure of the overlying perovskite. Here, a novel buried-interface strategy is proposed that incorporates A-site cations (FA(+) or Rb+) into the hole transport layer (HTL) to optimize perovskite crystallization. The introduction of A-site cations results in the formation of perovskite as seed at the interface, which effectively promotes the growth of the overlying perovskite with improved orientation, crystallinity, and rearranged phase distribution. Furthermore, an in-depth understanding of the influence of the crystallization process is tracked by in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) techniques. Meanwhile, it is found that that FA(+), due to the black phase alpha-FAPbI(3), is more suitable for optimizing the upper perovskite compared with Rb+ (delta-RbPbI3), and their incorporation can alter the structure of the PEDOT chains, thereby enhancing the carrier transport efficiency. With this approach, the 2D perovskite devices (n = 4) based on FACl-PEDOT:PSS achieve a remarkable power conversion efficiency (PCE) of 18.37%. The optimized device without encapsulation retains 87% of its initial efficiency after 1440 h of exposure in ambient.

As a typical carbon nanomaterial, graphdiyne (GDY) is expected to contribute to the field of nanozymes due to its unique structure and properties. However, the limited intrinsic enzyme-like activity of the pristine GDY nanomaterial suppressed its further development and application. In this paper, a heteroatom (Fe and N)-doping strategy was adopted to prepare GDY-based nanozymes. It has been found that heteroatom doping can improve the peroxidase-like activity of GDY nanomaterials, especially when Fe and N are codoped. The codoping of Fe and N not only increased the number of active sites, which could be uniformly distributed on the carbon substrate because of the coordination of N and Fe, but also changed the reactivity of substrates with nanozymes. As a result, the peroxidase-like activity of the Fe1.5-N-GDY nanozyme after the codoping of Fe and N into GDY was 18 times that of the N-GDY nanozyme and 14 times that of the Fe-1.5-GDY nanozyme. Moreover, the sensing application of the Fe-1.5-N-GDY nanozyme was explored in the determination of H2O2 and ascorbic acid (AA) through colorimetric assays, while the linear relationship was 100-800 and 800-2000 mu M with a detection limit of 52.96 mu M for H2O2 and was 5-100 mu M with a detection limit of 5.95 mu M for AA. This work provides not only an excellent peroxidase-like nanozyme for sensing but also a valuable reference for the design and synthesis of GDY-based nanozymes.

Electron transport layer (ETL) plays an important role in the perovskite solar cells. The graphdiyne oxide (GDYO), nitrogen-doped GDYO (NGDYO) or fluorinated GDYO (FGDYO) was added into SnO2 ETL, respectively, which optimized the properties of SnO2 layer itself and the interface between ETL and perovskite layer, and then affected the growth of perovskite. The mechanism was systematically explored by using in situ synchrotron radiation technology combined with conventional characterization methods. Though NGDYO-SnO2 enhanced the properties such as conductivity and energy level of ETL, FGDYO-SnO2 showed the best crystallization. By tracking the growth process of SnO2, PbI2 or perovskite by in situ XRD and the chemical bonds on the interface between ETL and active layer by in situ XAFS, it was found that the stronger interaction between the doped SnO2 with PbI2 inhibited PbI2 crystallization in perovskite layers and gave more opportunity for PbI2 precursor to form perovskite, making perovskite to have better crystallization. Finally, the optimized performance of device was achieved.

In this paper, a three-dimensional (3D) network Ag/MnO2/GO/PPy nanocomposite with adjustable micro-mesoporosity was synthesized by effectively controlling the amount of added pyrrole (Py). The Ag/MnO2/GO/PPy-5 nanocomposite exhibits excellent specific capacitance (C = 474.3 F g(-1), 5 mV s(-1)) and high cycle stability (up to 105.3% efficiency after 10,000 charge/discharge cycles). The appropriate micro-mesoporous structure of the 3D graphene-based nanocomposite provides a low-resistance path and a shorter diffusion path for ions, remarkably improving the electrochemical performance of Ag/MnO2/GO/PPy-5 by combining the advantages of these materials. Moreover, the 3D porous structure has strong stability, and evenly dispersed MnO2 and symbiose Ag nanoparticles can afford additional active sites and high conductivity for the nanocomposites.

The commonly reported calcination strategy usually requires high temperature to crack the metal-organic frameworks (MOFs) particles, which often lead to uncontrollable growth of nanomaterials. Here, for the first time, we utilize an electrochemical anion-exchanged method to control the hydrolysis of MOFs and synthesize porous Ni/Co hydroxide nanosheets. After the electrochemical anion-exchange, the organic ligands of MOFs nanosheets can be recycled and reused. Applying an electric field to the MOFs bulk in alkaline solution can accelerate the nucleation rate of hydroxide and change the migration behavior of charged ions/molecules, which can tailor the microstructure of derivatives and improve deep charge and discharge capability of the electrodes. As a result, the hydroxide with the optimized Ni:Co molar ratio of 7:3 and electric-field application time of 1000 cycles [Ni0.7Co0.3(OH)2-1000c] provides much better electrochemical properties than the materials synthesized without electric-field assistance: a high specific capacitance of 2115C g-1 (4230F g-1). A hybrid supercapacitor with the Ni0.7Co0.3(OH)21000c electrode shows a high energy density of 74.7 Wh kg-1, an improved power density (5,990.6 W kg-1), and an excellent cyclic stability (8,000 cycles). This study not only provides a novel strategy for the preparation of low-cost, deep-discharge electrodes for supercapacitors, but also proposes an unconventional method for mild synthesizing MOFs materials into porous nanoscale derivatives with tailored micromorphology. (c) 2021 Elsevier Inc. All rights reserved.

Lithium-sulfur (Li-S) batteries, as one of the most promising energy storage devices, have attracted widespread attentions due to their high theoretical energy density and environmental friendliness. However, the commercialized application of Li-S batteries is still restricted by several problems, including the dissolution of polysulfides in electrolyte and low conductivity of sulfur. Herein, a three-dimensional conductive cross-linked all-carbon network as a host matrix of sulfur is rationally designed and constructed using biomass silkworm faeces derived porous carbon (SFPC), reduction graphene oxide (rGO) and carbon nanotubes (CNTs) via a one-pot heat treatment approach. Meanwhile, it is found that the amounts of rGO and CNTs added have a great influence on the electrochemical properties of electrode. The optimum contents of CNTs and GO were explored, which are both 5% (the as-prepared material denoted as 55-PGC@SFPC). The obtained 55-PGC@SFPC/S with high content sulfur of 70% as a cathode of Li-S batteries exhibits the initial discharge capacity of 1354 mAh g(-1) at 0.1 C, excellent rate capacity of 478 mAh g(-1) at 3 C, admirable long-term cycling stability with a high reversible capacity of 414 mAh g(-1) after 1000 cycles and low capacity decay rate of 0.035% per cycle. The designed three-dimensional network structure could lead to a quick diffusion of Li+/e(-) and a good impeding effect for polysulfides dissolution, which is beneficial for developing the advanced energy storage device of Li-S batteries. (C) 2019 Elsevier Inc. All rights reserved.

To develop high-performance lithium-sulfur (Li-S) batteries, designing and exploring an advanced sulfur cathode with a conductive and polar robust framework is highly significant to suppress the "shuttle effect" of polysulfides and enhance the utilization of active sulfur. Herein, a multifunctional conductive nanohybrid, which acts as a sulfur host, is rationally constructed by inserting/intertwining carbon nanotubes (CNTs) onto Co-embedded N-doped porous dual carbon polyhedrons derived from a resorcinol-formaldehyde (RF) polymer layer enwrapping ZIF-67 metal-organic frameworks (MOFs) (Co, N-C@RFC/CNTs). The porous carbon polyhedrons can accommodate a high amount of sulfur owing to their large inner void space; the RF coating carbon layer and the CNTs effectively increase the conductivity and build a network for providing smooth ions/e(-) pathways; In addition, the polar Co particles and electronegative N heteroatoms synergistically strengthen the chemical adsorption of polysulfides and accelerate the redox reaction of the sulfur cathode. Benefiting from these advantages, the as-fabricated Co, N-C@RFC/CNTs/S cathode delivers a high reversible capacity of 1373.7 mAh g(-1) at 0.1 C, an impressive rate performance with 659.2 mAh g(-1) at 2.0 C, and an outstanding cycling stability with an ultralow capacity decay rate of 0.041 % per cycle for 500 cycles at 1.0 C. This work provides a facile and high-efficiency approach to fabricating excellent-performance storage materials based on an MOF precursor.

The electrochemical performance of carbon-based supercapacitor is closely related with the microscopic characteristics of electrode materials. Here, nitrogen-doped hierarchical porous carbons (NHPC) was fabricated by KOH treatment and pyrolyzation using pig nail as a protein-rich biomass source, and microscopic characteristics of the materials were effectively tailored by optimizing activation temperature to enhance electrochemical performance of carbonaceous materials for supercapacitor. The results show that the optimum activation temperature is 800 °C. The constructed NHPC-800 displays three-dimensional interconnected honeycomb structure, possesses high specific surface area (2563.30 m2 g−1) with high-speed ion transfer channels. Additionally, NHPC-800 deliver superior capacitance with 251.4 F g−1 at 1 A g−1. Besides, a remarkable energy density of 29.43 Wh kg−1 corresponding to power density of 847.9 W kg−1 is verified by an assembled symmetric supercapacitor in EMIMBF4 electrolyte.