A Sustainable Route to Ruthenium Phosphide (RuP)/Ru Heterostructures with Electron-Shuttling of Interfacial Ru for Efficient Hydrogen Evolution.

Ruthenium (Ru) is a promising electrocatalyst for the hydrogen evolution reaction (HER), despite suffering from low activity in non-acidic conditions due to the high kinetic energy barrier of H2O dissociation. Herein, the synthesis of carbon nanosheet-supported RuP/Ru heterostructures (RuP/Ru@CNS) from a natural polysaccharide is reported and demonstrates its behavior as an effective HER electrocatalyst in non-acidic conditions. The RuP/Ru@CNS exhibits low overpotential (106 mV at 200 mA·cm-2) in alkaline electrolyte, exceeding most reported Ru-based electrocatalysts. The electron shuttling between Ru atoms at the RuP/Ru interface results in a lowered energy barrier for H2O dissociation by electron-deficient Ru atoms in the pure Ru phase, as well as optimized H* adsorption of electron-gaining Ru atoms in the neighboring RuP. A low H* spillover energy barrier between Ru atoms at the RuP/Ru interface further boosts HER kinetics. This study demonstrates a sustainable method for the fabrication of efficient Ru-based electrocatalysts and provides a more detailed understanding of interface effects in HER catalysis.

The Use of Iron-Doped Anatase TiO2 Nanofibers for Enhanced Photocatalytic Fenton-like Reaction to Degrade Tylosin.

The removal of antibiotics from wastewater to prevent their environmental accumulation is significant for human health and ecosystems. Herein, iron (Fe)-atom-doped anatase TiO2 nanofibers (Fe-TNs) were manufactured for the photocatalytic Fenton-like decomposition of tylosin (TYL) under LED illumination. Compared with the pristine TiO2 nanofibers (TNs), the optimized Fe-TNs exhibited improved visible-light-driven photocatalytic Fenton-like activity with a TYL degradation efficiency of 98.5% within 4 h. The effective TYL degradation could be attributed to the expanded optical light absorption and accelerated separation and migration of photogenerated electrons and holes after the introduction of Fe. The photogenerated electrons were highly conducive to the generation of active SO4•- radicals as they facilitated Fe(III)/Fe(II) cycles, and to oxidizing TYL. Moreover, the holes could be involved in TYL degradation. Thus, a significant enhancement in TYL degradation could be achieved. This research verifies the use of iron-doped anatase nanofibers as an effective method to synthesize novel photocatalytic Fenton-like catalysts through surface engineering for wastewater remediation.

Tuning Electronic State and Charge Transport in B←N-Containing 2D Polymer Heterostructures with Efficient Photocatalytic Performance.

Linear-conjugated polymers (LCPs) are excellent semiconductor photocatalysts. However, its inherent amorphous structures and simple electron transport channels restrict efficient photoexcited charge separation and transfer. Herein, "2D conjugated engineering" is employed to design high-crystalline polymer photocatalysts with multichannel charge transport by introducing alkoxyphenyl sidechains. The electronic state structure and electron transport pathways of the LCPs are investigated using experimental and theoretical calculations. Consequently, the 2D B←N-containing polymers (2DPBN) exhibit excellent photoelectric characteristics, which enable the efficient separation of electron-hole and rapidly transfer photogenerated carriers to the catalyst surface for efficient catalytic reactions. Significantly, the further hydrogen evolution of 2DPBN-4F heterostructures can be achieved by increasing the fluorine content of the backbones. This study highlights that the rational design of LCP photocatalysts is an effective strategy to spur further interest in photofunctional polymer material applications.

Low temperature-resistant superhydrophobic and elastic cellulose aerogels derived from seaweed solid waste as efficient oil traps for oil/water separation.

Aerogel has excellent application potential in adsorption, heat preservation, and other areas due to its typical advantages of low density and high porosity. However, there are several issues with the use of aerogel in oil/water separation, including weak mechanical qualities and challenges in eliminating organic contaminants at low temperature. Inspired by cellulose Iα, which has excellent performance at low temperature, this study used cellulose Iα nanofibers extracted from seaweed solid waste as the skeleton, through covalent cross-linked with ethylene imine polymer (PEI) and hydrophobic modification of 1, 4-phenyl diisocyanate (MDI), supplemented by freeze-drying technology to form three-dimensional sheet, and successfully obtained cellulose aerogels derived from seaweed solid waste (SWCA). The compression test shows that the maximum compressive stress of SWCA is 61 kPa, and the initial performance still maintains 82% after 40 cryogenic compression cycles. In addition, the contact angles of water and oil on the surface of the SWCA were 153° and 0°, respectively, and the stable hydrophobic time in simulated seawater is more than 3 h. By combining the elasticity and superhydrophobicity/superoleophilicity, the SWCA with an oil absorption capacity of up to 11-30 times its mass, might be utilized repeatedly for the separation of an oil/water mixture.

Low-coordinated Co-N3 sites induce peroxymonosulfate activation for norfloxacin degradation via high-valent cobalt-oxo species and electron transfer.

The identification of reactive species in peroxymonosulfate (PMS) activation triggered by carbon-based single atom catalysts is the key to reveal the pollutant degradation mechanism. Herein, carbon-based single atom catalyst with low-coordinated Co-N3 sites (CoSA-N3-C) was synthesized to active PMS for norfloxacin (NOR) degradation. The CoSA-N3-C/PMS system exhibited consistent high performance for oxidizing NOR over a wide pH range (3.0-11.0). The system also achieved complete NOR degradation in different water matrixes, high cycle stability and excellent degradation performance for other pollutants. Theoretical calculations confirmed that the catalytic activity was derived from the favorable electron density of low-coordinated Co-N3 configuration, which was more conductive to PMS activation than other configurations. Electron paramagnetic resonance spectra, in-situ Raman analysis, solvent exchange (H2O to D2O), salt bridge and quenching experiments concluded that high-valent cobalt(IV)-oxo species (56.75%) and electron transfer (41.22%) contributed dominantly to NOR degradation. Moreover, 1O2 was generated in the activation process while not involved in pollutant degradation. This research demonstrates the specific contributions of nonradicals in PMS activation over Co-N3 sites for pollutant degradation. It also offers updated perceptions for rational design of carbon-based single atom catalysts with appropriate coordination structure.

Theoretical study of local S coordination environment on Fe single atoms for peroxymonosulfate-based advanced oxidation processes.

Tuning the electronic structure of single atom catalysts (SACs) is an effective strategy to promote the catalytic activity in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). Herein, a series of Fe-based SACs with S1/2/3/4-coordination numbers on graphene were designed to regulate the electronic structural of SACs at molecular level, and their effects on PMS activation were investigated via density function theory (DFT). The calculation results demonstrate that the electron structure of the active center can be adjusted by coordination environment, which further affects the activation of PMS. Among the studied Fe-SX-C4-X catalysts, with the increase of the S coordination number, the electron density of the Fe-SX-C4-X active center was optimized. The active center of the Fe-S4-C0 catalyst has a largest positive charge density, exhibiting the highest number of electron transfer. It also has a lower kinetic energy barrier (0.28 eV) for PMS dissociation. Organic pollutant such as bisphenol A (BPA) can achieve stable adsorption on Fe-SX-C4-X catalysts, which is conducive to subsequent oxidation by radicals. The dual index ∆f(r) indicates that the para-carbon atom of the hydroxyl group on the benzene ring of BPA is vulnerable to radical attack. This study highlights a theoretical support and a certain guide for designing efficient SACs to activate PMS.

An Unsaturated Bond Strategy to Regulate Active Centers of Metal-Free Covalent Organic Frameworks for Efficient Oxygen Reduction.

Unsaturated environment is the key to affect catalytic activity of the oxygen reduction reaction (ORR). Unveiling the effect of unsaturated sites toward ORR activity is of importance due to the vague unsaturated states. Reported here is a proof-of-concept strategy on the evaluation of unsaturated bonds (UBs) on adjacent carbon environment by precisely developing two metal-free vinyl-/azo-decorated covalent organic frameworks (Vinyl-COF and Azo-COF) as catalysts. The as-prepared UB-COFs exhibit good performance than the control Py-COF and comparable to the most reported carbon catalysts. Supported by theory calculations and in situ Raman spectra-electrochemistry, it is revealed that the UBs in organic catalysts can produce para-activation, identifying the para C=N groups as active centers. Importantly, the intrinsic UBs can induce local charge redistribution, and make the molecular skeleton possess high isosurface map distribution, with an efficient affinity for oxygen intermediates.

Effect of local coordination on catalytic activities and selectivities of Fe-based catalysts for N2 reduction.

Electrochemical reduction of nitrogen is considered a promising route for achieving green and sustainable ammonia synthesis under ambient conditions. A transition metal atom loaded on N-doped graphene is commonly used in the nitrogen reduction reaction (NRR), but the effect of the graphene's coordination environment on electron transfer has rarely been studied. Herein, the NRR performance of Fe1/2/3 clusters, anchored on single-vacancy and N-doped graphene, is investigated systematically via density functional theory (DFT). The calculation results show that the Fe2 cluster supported by two N atom-modified single-vacancy graphene displays the highest catalytic performance of NRR with the lowest energy barrier of 0.62 eV among the 12 candidates, and exhibits efficient selectivity. It has superior performance because of the highly asymmetrical distribution of electrons on graphene, the large positive charge of the Fe2, and the strong adsorption of *NNH. This study provides a new strategy to improve the NRR performance by regulating the Fe1/2/3 clusters coordination environment.

Electrostatic Interaction in Amino Protonated Chitosan-Metal Complex Anion Hydrogels: A Simple Approach to Porous Metal Carbides/N-Doped Carbon Aerogels for Energy Conversion.

In the face of the increasingly serious rapid depletion of fossil fuels, exploring alternative energy conversion technologies may be a promising choice to alleviate this crisis. Transition metal carbides (TMCs)/carbon composites are considered as prospective electrocatalysts due to their high catalytic activities and structural stability. In this work, we report the simple synthesis of TMCs/N-doping carbon aerogels (TMCs/NCAs, including Fe3C/NCA, Mo3C2/NCA, and Fe3C-Mo2C/NCA) for the oxygen reduction reaction (ORR) using protonated chitosan/metal complex anion-chelated aerogels. Among them, the Fe3C/NCA composite possesses efficient ORR activity (similar to Pt/C), and the Fe3C/NCA-assembled Zn-air battery exhibits high power densities of about 250 mW cm-2. The density functional theory calculation reveals that the presence of graphite-N, pyridine-N, and carbon defects in the carbon framework effectively reduces the free energy of ORR occurring in Fe3C. This work provides a simple and extensible strategy for the preparation of TMCs from chitosan, which is expected to be extended to other metal carbides.

Selenite capture by MIL-101 (Fe) through FeOSe bonds at free coordination Fe sites.

Selective immobilization of SeO32- is highly desired for the remediation of Se-contaminated water. Thus, the irreversible sorption of SeO32- ions by adsorbents through unique coordination bonds with high affinity is needed. Herein, we demonstrated that Fe-based metal-organic framework (MOF) (Fe-MIL-101) with free coordination sites (FCSs) enabled selective and irreversible capture of SeO32- ions from aqueous solution with fast kinetics and a high uptake capacity of 183.7 mg∙g-1, owing to large MOF apertures and substantial numbers of FCSs as capture sites through forming Fe-O-Se bonds. Meanwhile, Fe-MIL-101 maintained excellent performance in a broad pH range (4-11) and high selectivity for SeO32- ions in the presence of excessive competitive anions (e.g., CO32-, PO43-). Density functional theory (DFT) calculation, extended X-ray absorption fine structure (EXAFS), and Mössbauer fittings confirmed that the capture on Fe-MIL-101 was through the Fe-O-Se coordination bonds between FCSs and SeO32-. Moreover, Fe-MIL-101 could effectively remove SeO32- in simulated natural water and sewage by overcoming the influence of co-existing ions and organic matters. This study highlights new opportunities for the design of MOF-based materials for removing toxic and radioactive anions with irreversibility and high selectivity from natural and waste water.

Controlled Asymmetric Charge Distribution of Active Centers in Conjugated Polymers for Oxygen Reduction.

Active center reconstruction is essential for high performance oxygen reduction reaction (ORR) electrocatalysts. Usually, the ORR activity stems from the electronic environment of active sites by charge redistribution. We introduce an asymmetry strategy to adjust the charge distribution of active centers by designing conjugated polymer (CP) catalysts with different degrees of asymmetry. We synthesized asymmetric backbone CP (asy-PB) by modifying B←N coordination bonds and asymmetric sidechain CP (asy-PB-A) with different alkyl chain lengths. Both CPs with backbone and sidechain asymmetry exhibit superior ORR performance to their symmetric counterparts (sy-P and sy-PB). The asy-PB with greater asymmetry shows higher catalytic activity than asy-PB-A with relatively smaller asymmetry. DFT calculations reveal that the increased dipole moment and non-uniform charge distribution caused by asymmetric structure endows the center carbon atom of bipyridine with efficient catalytic activity.

Sodium-Decorated Amorphous/Crystalline RuO2 with Rich Oxygen Vacancies: A Robust pH-Universal Oxygen Evolution Electrocatalyst.

The oxygen evolution reaction (OER) is a key reaction for many electrochemical devices. To date, many OER electrocatalysts function well in alkaline media, but exhibit poor performances in neutral and acidic media, especially the acidic stability. Herein, sodium-decorated amorphous/crystalline RuO2 with rich oxygen vacancies (a/c-RuO2 ) was developed as a pH-universal OER electrocatalyst. The a/c-RuO2 shows remarkable resistance to acid corrosion and oxidation during OER, which leads to an extremely high catalytic stability, as confirmed by a negligible overpotential increase after continuously catalyzing OER for 60 h at pH=1. Besides, a/c-RuO2 also exhibits superior OER activities to commercial RuO2 and most reported OER catalysts under all pH conditions. Theoretical calculations indicated that the introduction of Na dopant and oxygen vacancy in RuO2 weakens the adsorption strength of the OER intermediates by engineering the d-band center, thereby lowering the energy barrier for OER.

Red Phosphorus Decorated TiO2 Nanorod Mediated Photodynamic and Photothermal Therapy for Renal Cell Carcinoma.

Clear cell renal cell carcinoma (ccRCC) is a serious and tenacious disease. Photodynamic therapy (PDT) and photothermal therapy (PTT) are effective means of cancer treatment. However, PDT combined with PTT has been rarely reported in ccRCC treatment. In the present study, by developing the core-shell structured TiO2 @red phosphorus nanorods (TiO2 @RP NRs) as a photosensitizer, the feasibility and effectiveness of synchronous PDT and PTT treatments for ccRCC are demonstrated. The core-shell structured TiO2 @RP NRs are synthesized to drive the PDT and PTT for ccRCC, in which the RP shell is the sensitizer even in the near-infrared (NIR) region. The optimized TiO2 @RP NRs can respond to NIR and produce local heat under irradiation. The NRs are estimated in ccRCC treatments via cell counting kit-8 assay, propidium iodide staining, qRT-PCR, and reactive oxygen species (ROS) probes in vitro, while terminal deoxynucleotidyl transferase dUTP nick-end labeling is conducted in vivo. After NIR irradiation, TiO2 @RP NRs can efficiently kill ccRCC cells by producing local heat and ROS and cause low injury to normal kidney cells. Furthermore, treatment with TiO2 @RP NRs and NIR can kill significant numbers of deep-tissue ccRCC cells in vivo. This work highlights a promising photo-driven therapy for kidney cancer.

Exploring the Dominant Role of Atomic- and Nano-Ruthenium as Active Sites for Hydrogen Evolution Reaction in Both Acidic and Alkaline Media.

Ru nanoparticles (NPs) and single atoms (SAs)-based materials have been investigated as alternative electrocatalysts to Pt/C for hydrogen evolution reaction (HER). Exploring the dominant role of atomic- and nano-ruthenium as active sites in acidic and alkaline media is very necessary for optimizing the performance. Herein, an electrocatalyst containing both Ru SAs and NPs anchored on defective carbon (RuSA+NP /DC) has been synthesized via a Ru-alginate metal-organic supramolecules conversion method. RuSA+NP /DC exhibits low overpotentials of 16.6 and 18.8 mV at 10 mA cm-2 in acidic and alkaline electrolytes, respectively. Notably, its mass activities are dramatically improved, which are about 1.1 and 2.4 times those of Pt/C at an overpotential of 50 mV in acidic and alkaline media, respectively. Theoretical calculations reveal that Ru SAs own the most appropriate H* adsorption strength and thus, plays a dominant role for HER in acid electrolyte, while Ru NPs facilitate the dissociation of H2 O that is the rate-determining step in alkaline electrolyte, leading to a remarkable HER activity.

Visible-light driven rapid bacterial inactivation on red phosphorus/titanium oxide nanofiber heterostructures.

Photocatalytic water disinfection has emerged as a promising approach for water purification. However, exploring efficient and rapid visible light driven materials for photocatalytic bacterial inactivation is still a challenging problem. Herein, red phosphorus/titanium oxide (TiO2@RP) nanofibers were developed for effective water disinfection by a vacuum ampoule strategy. The complete E. coli and S. aureus (7-log CFU mL-1) could be rapidly killed within 25 min and 30 min over the optimized TiO2@RP heterostructure under the white LED irradiation. The efficient photocatalytic antibacterial activity should be mainly ascribed to the synergetic enhancement in light absorption by RP decoration and charge migration and separation by the interface between TiO2 and RP. And then more unpaired photo-carriers would be transferred to the surface to facilitate the generation of photo-holes, •O2- radicals, and H2O2 species, which could destroy the bacterial cells efficiently.

Hydrogen Bond Interpenetrated Agarose/PVA Network: A Highly Ionic Conductive and Flame-Retardant Gel Polymer Electrolyte.

The gel polymer electrolyte (GPE) is the key to assembling high-performance solid-state supercapacitors (SSCs). The commercial poly(vinyl alcohol) (PVA) GPE has developed a reputation due to low ionic conductivity endowed by its high crystallinity and poor water retention capacity. In this work, density functional theory (DFT) calculations first revealed that the high crystallinity of PVA can be greatly disrupted by forming hydrogen bonds with natural agarose macromolecules. The hydrogen bond interpenetrated three-dimensional agarose/PVA network offers high water retention and large amounts of channels for movement of Li+ on hydroxyl oxygen atoms. So, an optimized formation of the Li-O coordinate bond (gLi-O(r) = 8.78) and improved diffusion coefficient of Li+ (DLi+) (71 × 10-6 cm2 s-1) were obtained in the agarose/PVA model. When assembled into SSCs, agarose/PVA-GPE with 2 M LiOAc (AP-GPE) exhibits an outstanding specific capacitance (697.22 mF cm-2 at 5 mA cm-2). The high water retention of agarose and large amounts of -OH groups in the agarose macromolecular can generate H2O by dehydration reaction, reducing the flammability of PVA and greatly enhancing the safety of SSCs.

Crystal Phase-Related Toxicity of One-Dimensional Titanium Dioxide Nanomaterials on Kidney Cells.

One-dimensional (1D) nanomaterials are widely used in different fields, and the increased application of 1D nanomaterials has drawn concerns about their unknown toxicity. 1D titanium oxide (TiO2) nanomaterials in different crystal phases are commonly applied in environmental remediation and solar energy conversion fields, but these materials pose a threat to human health, especially to the kidneys, an organ with abundant blood flow. To systematically evaluate the cytotoxicity to the kidneys, TiO2 nanofibers with TiO2(B), anatase, and rutile phases, as well as nanorods with anatase and rutile phases were synthesized and added to the culture medium of HK2 cells. Cell counting kit-8 assay, 2',7'-dichlorofluorescin diacetate assay, Hoechst 33342 staining experiments, and quantitative real-time reverse transcription polymerase chain reaction tests were used to explore the renal effects of the as-prepared TiO2 nanomaterials in the short term or long term. In the short-term evaluation, all the added TiO2 nanomaterials were toxic to HK2 cells, and the cytotoxicity was dose-dependent. Rutile TiO2 can widely attach to the cell surface and displays the most serious cell-killing and proapoptotic ability, while anatase induces the most serious oxidative stress. In long-term evaluation, all the as-prepared TiO2 nanomaterials led to epithelial mesenchymal transition (EMT), a mechanism of renal fibrosis. Consistent with the short-term results, rutile induced the most serious EMT. This study indicated that the renal toxicity of 1D TiO2 nanomaterials is crystal phase-dependent and that rutile induced the most significant renal cell injury. Oxidative stress is a crucial but not the only contributor to the renal toxicity of TiO2 nanomaterials in the short term.

Three-Dimensional Porous Alginate Fiber Membrane Reinforced PEO-Based Solid Polymer Electrolyte for Safe and High-Performance Lithium Ion Batteries.

The rational design and optimization of solid polymer electrolytes (SPEs) are critical for the application of safety and high efficiency lithium ion batteries (LIBs). Herein, we synthesized a novel poly(ethylene oxide) (PEO)-based SPE (PEO@AF SPE) with a cross-linking network by the introduction of alginate fiber (AF) membranes. Depending on the high-strength supporting AF skeleton and the cross-linking network formed by hydrogen bonds between the PEO matrix and AF skeleton, the obtained PEO@AF SPE exhibits an excellent tensile strength of 3.71 MPa, favorable heat resistance (close to 120 °C), and wide electrochemical stability window (5.2 V vs Li/Li+). Meanwhile, the abundant oxygen-containing groups in alginate macromolecular and the three-dimensional (3D) porous structure of the AF membrane can greatly increase Li+ anchor points and provide more Li+ migration pathways, leading to the enhancement of Li+ conduction and interfacial stability between the SPE and Li anode. Furthermore, the assembled LiFePO4/PEO@AF SPE/Li cells also exhibit satisfactory electrochemical performance. These results reveal that PEO incorporating with AFs can boost the mechanical strength, thermostability, and electrochemical properties of the SPE simultaneously. Furthermore, one will expect that the newly designed PEO@AF SPE with cross-linked networks thus provides the possibility for future applications of safety and high-performance LIBs.

Elemental red phosphorus-based materials for photocatalytic water purification and hydrogen production.

Semiconductor-based photocatalysis is a renewable and sustainable technology to solve global environmental pollution and energy shortage problems. It is essential to exploit highly efficient photocatalyst materials. Recently, Earth-abundant elemental red phosphorus (RP) with broader light-harvesting and appropriate band structure characteristics has been widely studied in photocatalysis. In this review, the crystal and electronic structures of RP (e.g., amorphous, Hittorf's and fibrous phosphorus) materials are firstly summarized along with the current advancement in the synthesis strategies of RP and RP-based materials in photocatalysis accompanied by a thorough discussion of the applications of RP-based materials in photocatalytic pollutant degradation, bacterial inactivation, and water splitting. Finally, this review also offers some guidance and perspectives for the future design of efficient visible-light-driven photocatalysts.

Multiple Vacancies on (111) Facets of Single-Crystal NiFe2 O4 Spinel Boost Electrocatalytic Oxygen Evolution Reaction.

Oxygen evolution reaction (OER) as the rate-determining reaction of water splitting has been attracting enormous attention. At present, only some noble-metal oxide materials (IrO2 and RuO2 ) have been reported as efficient OER electrocatalysts for OER. However, the high cost and scarcity of these noble-metal oxide materials greatly hamper their large-scale practical application. Herein, we synthesize 100% (111) faceted NiFe2 O4 single crystals with multiple vacancies (cation vacancies and O vacancies). The (111) facets can supply enough platform to break chemical bonds and enhance electrocatalytic activity, due to its high density of atomic steps and kink atoms. Compared to NiFe2 O4 (without vacancies), the as-synthesized NiFe2 O4 -Ar (with vacancies) exhibits a dramatically improved OER activity. The NiFe2 O4 -Ar-30 shows the lowest onset potential (1.45 V vs RHE) and the best electrocatalytic OER activity with the lowest overpotential of 234 mV at 50 mA cm-2 . Furthermore, based on the theoretical calculations that the introduction of multiple vacancies can effectively modulate the electronic structure of active centers to accelerate charge transfer and reaction intermediates adsorption, which can reduce the reaction energy barrier and enhance the activity of electrochemical OER.