4-Trifluorophenylammonium Iodide-Based Dual Interfacial Modification Engineering toward Improved Efficiency and Stability of SnO2-Based Perovskite Solar Cells.

Passivation engineering has been identified as an effective strategy to eliminate the targeted interfacial defects for improving the efficiency and stability of perovskite solar cells (PSCs). Herein, 4-trifluorophenylammonium iodide (CF3PhAI) is presented as a multifunctional passivation agent to modify buried SnO2/perovskite and perovskite/hole transport layer (HTL) interfaces. Upon incorporation of CF3PhAI between SnO2 and perovskite, CF3PhAI can chemically link to SnO2 via Lewis coordination and electrostatic coupling, thereby effectively passivating under-coordinated Sn and filling the oxygen vacancy. Meanwhile, CF3PhAI helps anchor PbI2 and organic cations (MA+/FA+) to control the crystallization of the perovskite. Consequently, reduced interfacial defects, homogeneous perovskite crystallites, and better energetic alignment can be simultaneously achieved. When CF3PhAI was further used to modify the perovskite/HTL interface, the fabricated PSCs yielded an impressive power conversion efficiency of 23.06% together with negligible J-V hysteresis. The unencapsulated devices exhibited long-term stability in wet conditions (91.8% efficiency retention after 1000 h) due to the water-resistant CF3PhAI. We also achieved good light soaking stability, maintaining 86.1% of its initial efficiency after aging for 720 h. Overall, our finding provides a promising strategy for modifying the dual contact interfaces of PSCs toward improved efficiency and stability.

Significant improvement on selectivity and capacity of glycine-modified FeCo-layered double hydroxides in the removal of As (V) from polluted water.

A series of novel Fe/Co layered double hydroxides modified with glycine (named as FeCo-LDH@G) were prepared and served as high-performance adsorbents for As (V). With a Fe/Co mole ratio of 1:1, the Fe0·02Co0.02-LDH@G adsorbents achieved significant improvements on the adsorption selectivity and capacity for As (V). The As (V) adsorption by Fe0·02Co0.02-LDH@G follows Langmuir isotherm model and pseudo-second-order kinetics model. The maximum adsorption capacity is 820 mg g-1 and the equilibrium reaches in 120 min. Under the assistance of electrochemical devices, the Fe0·02Co0.02-LDH@G adsorbent was regenerated and the adsorption capacity for As (V) was dropped only about 13.41% in 5 cycles. These excellent performances make Fe0·02Co0.02-LDH@G as promising As (V) adsorbents for commercial wastewater treatments.

A Smart Design Strategy for Super-Elastic Hydrogel with Long-Term Moisture, Extreme Temperature Resistance, and Non-Flammability.

Elastic hydrogel is a promising material category for designing biological muscles, repairable building materials, flexible electronic devices, and vulcanized rubber substitutes, which is required to have a long life, good self-healing performance and extreme temperature tolerance. Herein, a super-elastic mineral hydrogel is developed with long-lasting moisture, based on dynamic physical crosslinking between hydrated calcium ion clusters and amide groups of polyacrylamide (PAM). The complex hydrogel exhibits a super stretchability of 13 600% at room temperature, and can maintain the super flexibility in a wide temperature range of -40-50 °C or for a long period of 28 days. Particularly, the soft material cannot be ignited under an open flame at 400-500 °C, because of coupling dual flame retardant mechanisms containing the endothermic effect of liquid water evaporation and the barrier effect of calcium mineral salt on oxygen. In conclusion, the novel complex hydrogel with excellent tensile property, stability in extreme temperature or long operating time, and flame retardancy may become a promising candidate in the fields of agriculture, food, construction, medicine, and machinery.

Agaric-like anodes of porous carbon decorated with MoO2 nanoparticles for stable ultralong cycling lifespan and high-rate lithium/sodium storage.

The agaric-like anodes of porous carbon decorated with MoO2 nanoparticles (MoO2/C) for reversible Li/Na storage were synthesized via a green and facile bio-inspired route. The uniformly distributed MoO2 nanoparticles, the porous agaric-like carbon matrix and high degree graphitization of carbon materials, effectively mitigated the huge volume changes during cycling and improved the reversible capacity, resulting in the outstanding electrochemical behaviors with excellent rate capability, high capacity and excellent stable long cycling lifespan as anodes for lithium and sodium storage. Especially, the MoO2/C electrodes showed ultralong cycling performance under high current density of 5.0 A g-1, presenting a reversible capacity of 363.2 mAh g-1 after a prolonged 2000-cycles as anodes for Li storage. Meanwhile, the MoO2/C electrodes displayed a super-long cycling lifespan of 3000 cycles with the reversible discharge capacity of 193.5 mAh g-1 at the current density of 5.0 A g-1 for Na storage. Furthermore, the kinetic analysis of MoO2/C-4 electrodes as anodes for Li/Na storage was carried out to further investigate the electrochemical behavior. The ultralong cycling performance under high-density could satisfy the demands of next-generation anode electrodes for Li/Na ion batteries, promoting the commercialization process of MoO2-based materials.

Insights into Ion Occupancy Manipulation of Fe-Co Oxide Free-Standing Cathodes for Li-O2 Batteries with Enhanced Deep Charge Capability and Long-Term Capability.

The merits of Li-O2 batteries due to the huge energy density are shadowed by the sluggish kinetics of oxygen redox and massive side reactions caused by conductive carbon and a binder. Herein, Fe-Co inverse spinel oxide nanowires grown on Ni foam are fabricated as carbon-free and binder-free cathodes for Li-O2 batteries. Superior high rate cycle durability and deep charge capability are obtained. For example, 300 cycles with a low overpotential under a fixed capacity of 500 mAh g-1 are achieved at a high current density of 500 mA g-1. In the deep discharge/charge mode at 500 mA g-1, the optimized Fe-Co oxide cathode can stably work for more than 30 cycles with the capacity maintained at about 2100 mAh g-1. Owing to the appreciable incorporation of Fe3+ into the surface of stable inverse spinel oxides, the regulated Fe-Co oxide cathodes possess a more stable and higher ratio of Co3+/Co2+, which offers improved adsorption ability of reactive oxygen intermediates and thus achieves the enhanced electrocatalytic performance in the higher current density. In addition, the morphology evolution from array to pyramid-like structure of nanowires further provides assurance in the superior cycle capability. By coupling pyramid-shaped nanowires with binary inverse spinel, the obtained Fe-Co oxide becomes a promising material for practical applications in Li-O2 batteries. This work offers a general strategy to design efficient mixed metal oxide-based electrodes for the critical energy storage fields.

Optimizing graphene content in a NiSe/graphene nanohybrid counter electrode to enhance the photovoltaic performance of dye-sensitized solar cells.

Nickel selenide (NiSe) nanoparticles were grown on graphene nanosheets (GN) with different mass ratios to obtain their corresponding NiSe/GNx (x = 0.25 to 1.00) nanohybrids by a facile in situ hydrothermal process to integrate the advantages of the high specific surface area of graphene and the homogeneously immobilized catalytic sites of NiSe. The nanohybrid with a mass ratio of 1 : 0.50 (i.e., NiSe/GN0.50) exhibited higher electrocatalytic activity and electrolyte diffusion. Thus, NiSe/GN0.50 exhibited an improved photo-conversion efficiency (PCE) of 12% (η = 8.62%) compared to a standard Pt (η = 7.68%)-based dye-sensitized solar cell (DSSC). This improved PCE mainly originated from the catalytic ability of NiSe and the multiple interfacial electron transfer pathways of graphene, resulting in enhanced charge transfer and fast tri-iodide reduction kinetics at the counter electrode/electrolyte interface. The results obtained from the cyclic voltammetry (CV), electrochemical AC-impedance (EIS) and Tafel polarization studies validated the synergistic effects of NiSe and GN and the high potential of this nanohybrid as an efficient counter electrode (CE) for DSSCs.

Interfacial Engineering for High-Efficiency Nanorod Array-Structured Perovskite Solar Cells.

TiO2 nanorod (NR) array for perovskite solar cells (PSCs) has attained great importance due to its superb power conversion efficiency (PCE) compared to that of the traditional mesoporous TiO2 film. A TiO2 compact layer for the growth of TiO2 NR array via spin-coating cannot meet the requirements for efficient NR-based PSCs. Herein, we have developed and demonstrated the insertion of a bifunctional extrathin TiO2 interlayer (5 nm) by atomic layer deposition (ALD) at the interface of the fluorine-doped tin oxide (FTO)/TiO2 compact layer to achieve alleviated electron exchange and a reduced energetic barrier. Thus, an accelerated extraction of electrons from TiO2 NR arrays via the compact layer and their transfer to the FTO substrate can improve the PSC efficiency. The thickness of the spin-coated TiO2 compact layer on the ALD-deposited TiO2 layer is spontaneously optimized. Finally, an outstanding efficiency of 20.28% has been achieved from a champion PSC with negligible hysteresis and high reliability. To the best of our knowledge, this is the first study demonstrating the superiority of TiO2-NR-based PSCs withstanding the dry heat and thermal cycling tests. The results are of great importance for the preparation of efficient and durable PSCs for real-world applications.

Effects of Transition Metal Substituents on Interfacial and Electronic Structure of CH3NH3PbI3/TiO2 Interface: A First-Principles Comparative Study.

To evaluate the influence of transition metal substituents on the characteristics of CH3NH3PbI3/TiO2, we investigated the geometrical and electronic properties of transition metal-substituted CH3NH3PbI3/TiO2 by first-principles calculations. The results suggested that the substitution of Ti4+ at the five-fold coordinated (Ti5c) sites by transition metals is energetically favored. The substituted interface has enhanced visible light sensitivity and photoelectrocatalytic activity by reducing the transition energies. The transition metal substitution can effectively tune the band gap of the interface, which significantly improves the photo-reactivity. The substituted systems are expected to be more efficient in separating the photo-generated electrons-holes and active in the visible spectrum.

Anchoring carbon nanotubes and post-hydroxylation treatment enhanced Ni nanofiber catalysts towards efficient hydrous hydrazine decomposition for effective hydrogen generation.

For effective hydrogen generation with remarkable durability, carbon nanotubes (CNTs) grown on Ni nanofibers and their post hydroxylation treatment engendered active Ni nanofiber catalysts an efficient decomposition of hydrous hydrazine with a turnover frequency (TOF) of 19.4 h-1 and an activation energy down to 51.05 KJ mol-1.

Hydrothermally Synthesized Li4Ti5O12 Nanotubes Anode Material with Enhanced Li-Ion Battery Performances.

Hollow Li4Ti5O12 nanotubes were synthesized by stirring in a heated oil bath using P25 as titanium source and lithium hydroxide as lithium source. The as-prepared samples displayed a nanotube structure, with diameter of about 20~50 nm and length of 0.4 µm. The specific surface area of as-prepared samples reached 153.2 m²g-1. It is demonstrated that the Li4Ti5O12 nanotubes with improved performance can be obtained by hollow structure and high specific surface area. In consequence, it delivered a high reversible initial discharge capacity of 174.2 mAh g-1 at 0.5 C rate. A stable capacity of 170.9 mAh g-1 was delivered when the rate was reduced back to 0.5 C, suggesting good structural stability of the nanocable, high reversibility even after high rate charge- discharge, and good cycle stability. In addition, a capacity of 134.9 mAh g-1 and 98 mAhg-1 could be retained at a high rate of 5 C and 10 C, indicating excellent rate performances.

Progress on the Photocatalytic Reduction Removal of Chromium Contamination.

Rapid industrialization leads to increased wastewater discharge encompassing hexavalent chromium (Cr(VI)), which leads to serious environmental problems of toxicity and potential carcinogenicity. Removal of these species is normally carried out by ion-exchange, precipitation, membrane filtration, sorption, photocatalytic reduction, etc. This review mainly focuses on the photocatalytic and photoelectrocatalytic (PEC) reduction of Cr (VI), because of their advantages over other methods such as reduced risk of secondary pollution by non-reduced Cr (VI), no sludge formation, no need for a large amount of chemical reagents, clean and easy installation. The main factors influencing the photocatalytic reduction efficiency of Cr (VI) such as catalyst activity, solution pH, Cr adsorption on the catalyst and additives, are briefly discussed. Finally, a special emphasis is provided to the photoelectrocatalytic (PEC) reduction of Cr (VI).

Constructing efficient mixed-ion perovskite solar cells based on TiO2 nanorod array.

Oriented TiO2 nanorod array (TiO2 NA) is very attractive in the fields of halide perovskite solar cells (PSCs) due to its fewer grain boundaries and high crystallinity for effective charge collection. The optimization of TiO2 nanostructures has been proved to be an effective approach for efficient PSCs. On the other hand, tuning the crystallization of perovskite films on top of the TiO2 NA is very important for efficient TiO2-NA based PSCs. Herein, scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) were used to study the crystallization of different mixed-ion Cs0.1(FA0.83MA0.17)0.9Pb(I0.83Br0.17)3 perovskite (in which MA = CH3NH3+, and FA = CH(NH2)2+) films, from different perovskite precursor concentrations, on the TiO2 nanorod arrays. A mechanism was proposed to reveal the inherent connection between the precursor concentration and the crystallite growth of the perovskite film prepared with anti-solvent quenching process. Meanwhile, both faster charge separation at perovskite/TiO2 NA interface and longer charge transport were observed on thicker perovskite film with larger grains, revealed by the time-resolved method. However, atomic force microscopy (AFM) results indicated that too thick perovskite film impaired the charge collection owing to the increased recombination. By balancing the charge collection and film thickness, highly efficient PSCs were prepared with a champion power conversion efficiency (PCE) of 19.33% with little hysteresis. The study highlights a great potential of incorporating oriented one-dimensional electron extraction materials in high-performance PSCs and other applications.

Structural characterization of lignin and its carbohydrate complexes isolated from bamboo (Dendrocalamus sinicus).

Isolation of earth abundant biopolymer, Lignin, from Dendrocalamus sinicus and their structural properties were investigated to achieve its large-scale practical applications in value-added products. Two lignin fractions (MWL, DSL) were isolated with successive treatments of dioxane and dimethylsulfoxide (DMSO) from dewaxed and ball milled bamboo (D. sinicus) sample. The two-step treatments yielded 52.1% lignin based on the total lignin content in the dewaxed bamboo sample. Spectroscopy analyses indicated that the isolated bamboo lignin was a typical grass lignin, consisting of p-hydroxyphenyl, guaiacyl, and syringyl units. The major interunit linkages presented in the obtained bamboo lignin were ß-O-4' aryl ether linkages, together with lower amounts of ß-ß', ß-5', and ß-1' linkages. The tricin was detected to be linked to lignin polymer through the ß-O-4' linkage in the bamboo. In addition, phenyl glycoside and benzyl ether lignin-carbohydrate complexes (LCC) linkages were clearly detected in bamboo (D. sinicus), whereas the γ-ester LCC linkages were ambiguous due to the overlapping NMR signals with other substructures. The detailed structural properties of the obtained lignin fraction together with the light-weight will benefit efficient utilization of natural polymers as a possibly large-scale bio-based precursor for making polymeric materials, biochemicals, functional carbon and biofuels, and multifunctional polymer nanocomposites.

Carbon nanotube aerogel-CoS2 hybrid catalytic counter electrodes for enhanced photovoltaic performance dye-sensitized solar cells.

The carbon nanotube aerogel (CNA) with an ultra-low density, three-dimensional network nanostructure, superior electronic conductivity and large surface area is being widely employed as a catalytic electrode and catalytic support. Impressively, dye-sensitized solar cells (DSSCs) assembled with a CNA counter electrode (CE) achieved a maximum power conversion efficiency (PCE) of 8.28%, which exceeded that of the conventional platinum (Pt)-based DSSC (7.20%) under the same conditions. Furthermore, highly dispersed CoS2 nanoparticles endowed with excellent intrinsic catalytic activity were hydrothermally incorporated to form a CNA-supported CoS2 (CNA-CoS2) CE, which was due to the large number of catalytically active sites and sufficient connections between CoS2 and the CNA. The electrocatalytic ability and stability were systematically evaluated by cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and Tafel polarization, which confirmed that the resultant CNA-CoS2 hybrid CE exhibited a remarkably higher electrocatalytic activity toward I3- reduction, and faster ion diffusion and electron transfer than the pure CNA CE. Such cost-effective DSSCs assembled with an optimized CNA-CoS2 CE yielded an enhanced PCE of 8.92%, comparable to that of the cell fabricated with the CNA-Pt hybrid CE reported in our published literature (9.04%). These results indicate that the CNA-CoS2 CE can be considered as a promising candidate for Pt-free CEs used in low-cost and high-performance DSSCs.

Synthesis and photoelectrocatalytic activity of In2O3 hollow microspheres via a bio-template route using yeast templates.

Indium oxide (In2O3) hollow microspheres were prepared using yeast as a bio-template with the aid of a precipitation method. The yeast provided a solid frame for the deposition of In(OH)3 to form the precursor. The resulting In2O3 hollow microspheres were obtained by calcining the precursor at 650 °C. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms and UV-Vis diffuse reflectance spectroscopy. The results showed that the diameter of the In2O3 hollow microspheres was about 2.0-3.0 µm and the spherical shells were composed of In2O3 nanoparticles with a size of ∼20 nm. The BET specific surface area of the sample was 19.23 m2 g-1. The photoelectrocatalytic test results showed that the photoelectrocatalytic degradation efficiency of methylene blue (MB) using In2O3 hollow microspheres as catalysts under visible light irradiation and a certain voltage could reach above 95% after 4 hours, much higher than that of only photodegradation. The enhanced photoelectrocatalytic activity could be attributed to the hydroxyl radicals HO˙ produced by the light irradiation reaction process which could oxidize the electron donors and were beneficial to reducing the recombination of electrons and holes.