Ru-P pair sites boost charge transport in hematite photoanodes for exceeding 1% efficient solar water splitting.

Fast transport of charge carriers in semiconductor photoelectrodes are a major determinant of the solar-to-hydrogen efficiency for photoelectrochemical (PEC) water slitting. While doping metal ions as single atoms/clusters in photoelectrodes has been popularly used to regulate their charge transport, PEC performances are often low due to the limited charge mobility and severe charge recombination. Here, we disperse Ru and P diatomic sites onto hematite (DASs Ru-P:Fe2O3) to construct an efficient photoelectrode inspired by the concept of correlated single-atom engineering. The resultant photoanode shows superior photocurrent densities of 4.55 and 6.5 mA cm-2 at 1.23 and 1.50 VRHE, a low-onset potential of 0.58 VRHE, and a high applied bias photon-to-current conversion efficiency of 1.00% under one sun illumination, which are much better than the pristine Fe2O3. A detailed dynamic analysis reveals that a remarkable synergetic ineraction of the reduced recombination by a low Ru doping concentration with substitution of Fe site as well as the construction of Ru-P bonds in the material increases the carrier separation and fast charge transportation dynamics. A systematic simulation study further proves the superiority of the Ru-P bonds compared to the Ru-O bonds, which allows more long-lived carriers to participate in the water oxidation reaction. This work offers an effective strategy for enhancing charge carrier transportation dynamics by constructing pair sites into semiconductors, which may be extended to other photoelectrodes for solar water splitting.

Enhanced Charge-carrier Dynamics and Efficient Photoelectrochemical Nitrate-to-ammonia Conversion on Antimony Sulfide-based Photocathodes.

The photoelectrochemical reduction of nitrate to ammonia (PEC NO3RR) has emerged as a promising pathway for facilitating the natural nitrogen cycle. The PEC NO3RR can lower the reduction potential needed for ammonia synthesis through photogenerated voltage, showcasing the significant potential for merging abundant solar energy with sustainable nitrogen fixation. However, it is influenced by the selective photocathodes with poor carrier kinetics, low catalytic selectivity, and ammonia yields. There are few reports on suitable photoelectrodes owning efficient charge transport on PEC NO3RR at low overpotentials. Herein, we rationally constructed the CuSn alloy co-catalysts on the antimony sulfides with a highly selective PEC ammonia and an ultra-low onset potential (0.62 VRHE). CuSn/TiO2/Sb2S3 achieved an ammonia faradic efficiency of 97.82% at a low applied potential of 0.4 VRHE, and an ammonia yield of 16.96 µmol h-1 cm-2 at 0 VRHE under one sun illumination. Dynamics experiments and theoretical calculations have demonstrated that CuSn/TiO2/Sb2S3 has an enhanced charge separation and transfer efficiency, facilitating photogenerated electrons to participate in PEC NO3RR quickly. Meanwhile, moderate NO2* adsorption on this photocathode optimizes the catalytic activity and increases the NH4+ yield. This work opens an avenue for designing sulfide-based photocathodes for the efficient route of solar-to-ammonia conversion.

Review on Cell Structure Regulation and Performances Improvement of Porous Poly(Lactic Acid).

Recent advances in the cell structure regulation and performances improvement of porous poly(lactic acid) materials (PPMs) are systematically reviewed in this feature article. First, the typical processing methods, including template method, non-solvent induced phase separation, freeze-drying, and supercritical CO2  foaming, of PPMs are introduced emphatically. Their various cell morphologies by different processing methods are summarized: finger-like, honeycomb-like, fiber-like, through cell, open cell, closed cell, ball-like, and flower-like. Meanwhile, the transformation among different cell morphologies as well as the changes in cell size and cell density, having impact on the performances, is described. Second, the influence of stereo-complex crystals on the cell structure of PPMs is emphatically reviewed. Furthermore, the relationships between cell structure and properties that includes mechanical properties, thermal stability, heat insulation, and hydrophobicity, are elaborated. Eventually, the issues of PPMs worthy of further study are discussed.

Size Regulation of Polydopamine Nanoparticles by Boronic Acid and Lewis Base.

Size regulation of polydopamine nanoparticles (PDA NPs) is vital to melanin-inspired materials. The general strategy usually focuses on tuning of the reaction parameters which could affect the dopamine (DA) monomer polymerization process, such as pH, temperature, monomer concentration, etc. The reaction between boronic acids and catechols to form boronic esters has been widely applied in many fields, but little attention has been paid in the size regulation of PDA NPs. Here, it is speculated that the fine size regulation of PDA NPs can be directly achieved by using boronic acids and Lewis base molecules. It is found that these issues could indeed significantly affect the stability of the boronic esters formed by boronic acids and DA, which may further inhibit the monomer polymerization kinetics and tune the particle size of the resulting PDA NPs. It is also found that the several intrinsic properties of PDA NPs such as the free radical scavenging ability, UV spectral absorption, photothermal behavior, and structural color all change with the particle size. It is believed that this work can provide new opportunities for fabricating melanin-inspired PDA NPs with well controlled size and properties.

Superhydrophobic Thermoplastic Polyurethane Foam Fabricated by Phase Separation and Silica Coating for Oil-Water Separation.

Oil spills and the presence of oily wastewater have resulted in substantial ecological damage. Superhydrophobic polymer foam with selectivity and adsorption capacity is a promising candidate for efficient oil-water separation. In this study, a method that combines phase separation and silica coating to produce superhydrophobic thermoplastic polyurethane (TPU) foam is proposed. The TPU foam demonstrates superhydrophobicity with a water contact angle of 155.62°, and exhibits a maximum saturated adsorption capacity of 54.11 g g-1 . Furthermore, the foam can be utilized as a filter for oil-water separation, maintaining its filtration efficiency (41.2 m3  m2  h-1 ) even after ten filtration cycles.

Effect of Solvent Polarity on the Spectral Characteristics of 5,10,15,20-Tetrakis(p-hydroxyphenyl)porphyrin.

The electronic absorption and vibrational spectra of deprotonated 5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (THPP) are studied as a function of solvent polarity in H2O-DMF, H2O-acetone, H2O-methanol, and DMF-acetone mixtures. The maximum absorption wavelength (λmax) of the lowest energy electronic absorption band of deprotonated THPP shows an unusual solvatochromism-a bathochromic followed by a hypsochromic shift with reduced polarity. According to the correlation analysis, both specific interactions (H-bonds) and nonspecific interactions affect the spectral changes of this porphyrin. Furthermore, the solvent polarity scale ET(30) can explain both shifts very well. At higher polarity (ET(30) > 48), THPP exists as a hyperporphyrin. The ET(30) is linear with λmax and a decrease in solvent polarity is accompanied by a bathochromic shift of λmax. These results can be rationalized in terms of the cooperative effects of H-bonds and nonspecific interactions on the spectra of hyperporphyrin. At relatively low polarity (45.5 < ET(30) < 48), hyperporphyrin gradually becomes Na2P as ET(30) reaches the critical value of 45.5. The spectrum of the hyperporphyrin turns into the three-band spectrum of the metalloporphyrin, which is accompanied by a hypsochromic shift of λmax.

Magnetic Interacted Interaction Effect in MXene Skeleton: Enhanced Thermal-Generation for Electromagnetic Interference Shielding.

With the rapid advancements of portable and wearable equipment, high-efficiency electromagnetic interference (EMI) shielding materials are highly entailed to eliminate radiated electromagnetic pollution. Herein, by assembling hexagonal SrFe12 O19 flakes into a Ti3 C2 Tx MXene/MWCNT substrate, a magnetized Ti3 C2 Tx -based film is successfully fabricated by a facile filtration approach. Carbon nanotubes are used as isolation agents to realize the submicroscopic dispersion of MXene and SrFe12 O19 . The obtained MXene/MWCNTs/SrFe12 O19 film shows a high electrical conductivity of 438 S cm-1 and an excellent EMI shielding effectiveness of 62.9 dB in X-band at a thickness of only 40 µm. Benefiting from a strong magnetic response ability and an expanded magnetic coupling space, hexagonal SrFe12 O19 sheets can efficiently consume incident magnetic field energy by domain wall migration and the ferromagnetic resonance effect. Boosted EMI shielding performance can be achieved by improving the magnetic loss in the Ti3 C2 Tx MXene/MWCNTs/SrFe12 O19 film, preventing the secondary reflection of electromagnetic waves. Meanwhile, magnetized MXene-based films display the freestanding and flexible features and are suitable for installation in electric devices. It is anticipated that this strategy offers new ideas for designing EMI shielding films and in broadening potential utility of MXene-based materials.

Fine modulation of the energy band strategy to control the carrier confinement capability of digital alloys.

In this paper, a strategy to finely modulate the energy band structure to control the carrier confinement capability of digital alloys (DA) is proposed. Strain analysis shows that As and Sb atoms are exchanged within the AlAsSb DA. The bottom of the corrected potential well is low on the left and high on the right in the growth direction, resulting in a higher band offset of the AlSb potential barrier layer on the left side of the potential well than on the right side. The modulation of the band leads to a higher probability of electron tunneling in DA under the action of an electric field opposite to the growth direction. Conversely, it is difficult for the electrons to tunnel into the lower energy level potential wells. TheI-Vcurve of DA shows that the current value under positive bias is significantly smaller than the value under negative bias when the voltage is higher. The measured results correspond perfectly with the modified energy band model, which verifies the feasibility of energy band modulation. This is important for the structural design of DA and the reduction of dark current in optoelectronic devices.

Simple Design of a Porous Solar Evaporator for Salt-Free Desalination and Rapid Evaporation.

Solar-driven interfacial evaporation is considered to be one of the promising and efficient ways of producing clean water in recent years. However, it remains a challenge to develop solar evaporation devices with high solar evaporation rates and salt-free blocking properties. Here, a porous solar evaporator with directed water transport and salt-free desalination through excellent photothermal conversion and purposefully guided migration of the salt solution was developed. The designed porous photothermal sponge with the synergistic effect of MXene and polypyrrole can achieve evaporation rates of 1.47 and 2.27 kg m-2 h-1, respectively, in the capillary model and siphon model water-transporting solar evaporation devices. More interestingly, the designed zigzag-shaped device with an evaporation rate of 2.45 kg m-2 h-1 was achieved. In addition, the evaporator can operate stably under 9 h in the siphon model solar evaporation device and achieves the effect of salt-free desalination. The above design provides a good strategy for solar-powered desalination applications.

Oil-Water Separation Polypropylene Foam with Advanced Solvent-Evaporation Induced Coexistence of Microspheres and Microporous Structure.

For decades, crude oil spills and oil wastewater have become the most problematic environmental pollution and damage to public health. Therefore, it is considerable to develop superhydrophobic polymer foam for separating oil from water with high selectivity and sorption capacity. Here, a new type of environmentally friendly pure polypropylene (PP) foam with superhydrophobicity is first time proposed with a particular coexistence of microspheres and microporous structure fabricated via an advanced solvent-evaporation method. The PP foam exhibits exceptional superhydrophobic with a water contact angle of 151° and the maximum saturated adsorption capacity of 26 g g-1 . After more than 15 h of cyclic continuous oil-water pumping experiment, it still maintains a high oil absorption efficiency of 98%, providing the basis for practical commercial applications. More importantly, the variation of hydrophobic properties is described by Flory-Huggins polymer solution theory and Huggins interaction parameters, and the optimal solution ratio range is predicted which provides a relevant theoretical basis for actual industrial production.

Interfacial Strain Engineering in Wide-Bandgap GeS Thin Films for Photovoltaics.

Wide-bandgap semiconductors exhibiting a bandgap of ∼1.7-1.9 eV have generated great interest recently due to their important applications in tandem solar cells as top cells and emerging indoor photovoltaics. However, concerns about the stability and toxicity especially in indoor application limit the choice of these materials. Here we report a new member of this family, germanium monosulfide (GeS); this material displays a wide bandgap of 1.7 eV, nontoxic and earth-abundant constituents, and high stability. We find that the little success of GeS solar cells to date is primarily attributed to the challenge in fabricating high-quality polycrystalline GeS films, wherein the high thermal expansion coefficient (α = 3.1 × 10-5 K-1) combined with high crystallization temperature (375 °C) of GeS induces large tensile strain in the GeS film that peels off GeS from the substrate. By introducing a high-α buffer layer between GeS and substrate, we achieve a high-quality polycrystalline GeS thin film that compactly adheres to substrate with no voids. Solar cells fabricated by these GeS films show a power conversion efficiency of 1.36% under AM 1.5G illumination (100 mW cm-2). The unencapsulated devices are stable when stored in ambient atmosphere for 1500 h. Their efficiencies further increase to 3.6% under indoor illumination of 1000 lux.

Enhanced Surface Ligands Reactivity of Metal Clusters by Bulky Ligands for Controlling Optical and Chiral Properties.

Surface ligands play critical roles in determining the surface properties of metal clusters. However, modulating the properties and controlling the surface structure of clusters through surface-capping-agent displacement is challenging. Herein, [Ag14 (SPh(CF3 )2 )12 (PPh3 )4 (DMF)4 ] (Ag14 -DMF; DMF=N,N-dimethylformamide), with weakly coordinated DMF ligands on surface silver sites, was synthesized by a mixed-ligands strategy. Owing to the high surface reactivity of Ag14 -DMF, the surface ligands are labile, easily dissociated or exchanged by other ligands. Based on the enhanced surface reactivity, easy modulation of the optical properties of Ag14 by reversible "on-off" DMF ligation was realized. When chiral amines were introduced to as-prepared products, all eight surface ligands were replaced by amines and the racemic Ag14 clusters were converted to optically pure homochiral Ag14 clusters as evidenced by circular dichroism (CD) activity and single-crystal X-ray diffraction (SCXRD). This work provides a new insight into modulation of the optical properties of metal clusters and atomically precise homochiral clusters for specific applications are obtained.

Photo-driven Oxygen Vacancies Extends Charge Carrier Lifetime for Efficient Solar Water Splitting.

A photocharge/discharge strategy is proposed to initiate the WO3 photoelectrode and suppress the main charge recombination, which remarkably improves the photoelectrochemical (PEC) performance. The photocharged WO3 surrounded by a 8-10 nm overlayer and oxygen vacancies could be operated more than 25 cycles with 50 h durability without significant decay on PEC activity. A photocharged WO3 /CuO photoanode exhibits an outstanding photocurrent of 3.2 mA cm-2 at 1.23 VRHE with a low onset potential of 0.6 VRHE , which is one of the best performances of p-n heterojunction structure. Using nonadiabatic molecular dynamics combined with time-domain DFT, we clarify the prolonged charge carrier lifetime of photocharged WO3 , as well as how electronic systems of photocharged WO3 /CuO semiconductors enable the effective photoinduced electrons transfer from WO3 into CuO. This work provides a feasible route to address excessive defects existed in photoelectrodes without causing extra recombination.

Tertiary Chiral Nanostructures from C-H⋠⋠⋠F Directed Assembly of Chiroptical Superatoms.

We report the synthesis and structure of tertiary chiral nanostructures with 100 % optical purity. A novel synthetic strategy, using chiral reducing agent, R and S-BINAPCuBH4 (BINAP is 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl), is developed to access to atomically precise, intrinsically chiral [Au7 Ag6 Cu2 (R- or S-BINAP)3 (SCH2 Ph)6 ]SbF6 nanoclusters in one-pot synthesis. The clusters represent the first tri-metallic superatoms with inherent chirality and fair stability. Both metal distribution (primary) and ligand arrangement (secondary) of the enantiomers exhibited perfect mirror images, and unprecedentedly, the self-assembly driven by the C-H⋅⋅⋅F interaction between the phenyl groups of the superatom moieties and SbF6 - anions induced the formation of bio-mimic left- and right-handed helices, achieving the tertiary chiral nanostructures. DFT calculations revealed the connections between the molecular details and chiral optical activity.

Encapsulation of Sulfur into N-Doped Porous Carbon Cages by a Facile, Template-Free Method for Stable Lithium-Sulfur Cathode.

Lithium-sulfur (Li-S) batteries with a high energy density and long lifespan are considered as promising candidates for next-generation electrochemical energy-storage devices. However, the sluggish redox kinetics of electrochemistry and high solubility of polysulfide during cycling render insufficient sulfur utilization and poor cycling stability. Herein, a facile, template-free procedure based on controlled pyrolysis of polydopamine vesicles is described to prepare N-doped porous carbon cages (NHSC) as a new sulfur host, which significantly improves both the sulfur utilization and cycling stability. As NHSC shows a high pore volume, continuous electron and ion transport paths, and good catalytic activity, encapsulation of S nanoparticles into NHSC endows the resulting S@NHSC electrode with a good energy storage capacity and exceptionally high electrochemical stability. Consequently, a Li-S cell with the S@NHSC as the cathode achieves a high initial capacity of 1280.7 mAh g-1 , and cycling stability over 500 cycles with the capacity decay as low as 0.0373% per cycle.

Porous α-Fe2O3 nanoparticles encapsulated within reduced graphene oxide as superior anode for lithium-ion battery.

A facile route for the controllable synthesis of porous α-Fe2O3 supported by three-dimensional reduced graphene oxide (rGO) is presented. The synergistic effect between α-Fe2O3 and rGO can increase the electrolyte infiltration and improve lithium ion diffusion as well. Moreover, the combination of rGO nanosheets can increase the available surface area to provide more active sites and prevent α-Fe2O3 nanoparticles from agglomeration during the cycling process to ensure its long-term cycle performance. Consequently, the α-Fe2O3/rGO nanocomposites exhibit higher reversible specific capacity (1418.2 mAh g-1 at 0.1 A g-1), better rate capability (kept 804.5 mAh g-1 at 5.0 A g-1) and cycling stability than the α-Fe2O3 nanoparticles. Owing to the superior electrochemical performance, the α-Fe2O3/rGO nanocomposites might have a great potential as anode for lithium-ion batteries.

Towards Long-Term Photostability of Nickel Hydroxide/BiVO4 Photoanodes for Oxygen Evolution Catalysts via In†Situ Catalyst Tuning.

Increasing long-term photostability of BiVO4 photoelectrode is an important issue for solar water splitting. The NiOOH oxygen evolution catalyst (OEC) has fast water oxidation kinetics compared to the FeOOH OEC. However, it generally shows a lower photoresponse and poor stability because of the more substantial interface recombination at the NiOOH/BiVO4 junction. Herein, we utilize a plasma etching approach to reduce both interface/surface recombination at NiOOH/BiVO4 and NiOOH/electrolyte junctions. Further, adding Fe2+ into the borate buffer electrolyte alleviates the active but unstable character of etched-NiOOH/BiVO4 , leading to an outstanding oxygen evolution over 200 h. The improved charge transfer and photostability can be attributed to the active defects and a mixture of NiOOH/NiO/Ni in OEC induced by plasma etching. Metallic Ni acts as the ion source for the in situ generation of the NiFe OEC over long-term durability.

In situ fabrication of a luminescent copper nanocluster/eggshell membrane composite and its application in visual detection of Ag+ ions, light-emitting diodes and surface patterning.

In this work, we report a novel strategy for fabricating a luminescent 2D nanocomposite at room temperature by in situ generation of luminescent copper nanoclusters (Cu NCs) embedded in natural monolithic eggshell membrane (ESM) using dithiothreitol as the reducing and capping agent. The established fabrication is facile, cost-effective and viable. The as-prepared Cu NC/ESM nanocomposite exhibited excellent photoluminescence performance, improved chemical, thermal and photo stability, convenient tailoring and flexibility. Significantly, the nanocomposites could be employed as test strips for the visual detection of Ag+ ions based on the luminescence quenching phenomenon and as color conversion layers in light-emitting diodes. Furthermore, application of the proposed strategy for surface luminescence patterning was well demonstrated, indicating great potential in biomass based anti-counterfeiting, information encryption and security paper or sheets.

Facile Thermally Impacted Water-Induced Phase Separation Approach for the Fabrication of Skin-Free Thermoplastic Polyurethane Foam and Its Recyclable Counterpart for Oil-Water Separation.

Developing a facile large-scale strategy to fabricate polymer foams with excellent wettability and recycling its counterpart for oil-water separation is in urgent demand. Here, a facile template-free thermally impacted water-induced phase separation approach for the fabrication of skin-free thermoplastic polyurethane foam with a water contact angle of 147°, porosity more than 90%, density less than 14 mg cm-3 , and excellent compressibility (>1000 cycles) is proposed. The foams show high efficiency of oil recovery (>98%) during the squeezing and pumping oil-water separation test. Moreover, the used foams could be recycled and reused to form refresh foams without sacrificing their high performance, which makes this method a promising prospect for environmental applications.

How Partial Atomic Charges and Bonding Orbitals Affect the Reactivity of Aluminum Clusters with Water?

We present here a further insight on the hydrogen evolution reactions (HER) of aluminum clusters with one and multiple water molecules. Along with natural bond orbital (NBO) and frontier molecular orbital (FMO) analysis, we compared the reactivities of both anionic and neutral Al13, Al12, Al7, and Al6 clusters with water in gas phase. It is found that electron flow interactions between these typical Al clusters and H2O initiate their reactions, allowing varied charge distribution on the cluster. With an emphasis on the typical Al6 cluster, we checked out the reactive intermediates, activated complexes, transition states, bond breaking and stereochemistry for it to react with two and four water molecules, respectively. The kinetic- and thermodynamic- allowed reaction pathways are coincident with the experimental observation of Al n(OH)4- being dominant products for Al n- clusters reacting with water. It is illustrated how additional water molecules function as catalysts enabling strengthened HER activity.