Activation of α-Fe2 O3 for Photoelectrochemical Water Splitting Strongly Enhanced by Low Temperature Annealing in Low Oxygen Containing Ambient.

Photoelectrochemical (PEC) water splitting is a promising method for the conversion of solar energy into chemical energy stored in the form of hydrogen. Nanostructured hematite (α-Fe2 O3 ) is one of the most attractive materials for a highly efficient charge carrier generation and collection due to its large specific surface area and the short minority carrier diffusion length. In the present work, the PEC water splitting performance of nanostructured α-Fe2 O3 is investigated which was prepared by anodization followed by annealing in a low oxygen ambient (0.03 % O2 in Ar). It was found that low oxygen annealing can activate a significant PEC response of α-Fe2 O3 even at a low temperature of 400 °C and provide an excellent PEC performance compared with classic air annealing. The photocurrent of the α-Fe2 O3 annealed in the low oxygen at 1.5 V vs. RHE results as 0.5 mA cm-2 , being 20 times higher than that of annealing in air. The obtained results show that the α-Fe2 O3 annealed in low oxygen contains beneficial defects and promotes the transport of holes; it can be attributed to the improvement of conductivity due to the introduction of suitable oxygen vacancies in the α-Fe2 O3 . Additionally, we demonstrate the photocurrent of α-Fe2 O3 annealed in low oxygen ambient can be further enhanced by Zn-Co LDH, which is a co-catalyst of oxygen evolution reaction. This indicates low oxygen annealing generates a promising method to obtain an excellent PEC water splitting performance from α-Fe2 O3 photoanodes.

Activated mesoporous carbon nanofibers fabricated using water etching-assisted templating for high-performance electrochemical capacitors.

Activated mesoporous carbon nanofibers (AMCNFs) are synthesized by a sequential process of electrospinning, water etching-assisted templating, and acid treatment. Their morphologies, crystal structures, melting behavior, chemical bonding states, surface properties, and electrochemical performance are investigated for three different polyacrylonitrile (PAN) to polyvinylpyrrolidone (PVP) weight ratios - PAN : PVP = 8 : 2, 7 : 3, and 6 : 4. Compared to other samples, the AMCNFs with an optimum weight ratio of 6 : 4 show the highest specific surface area of 692 m(2) g(-1), a high volume percentage of mesopores of 43.9%, and an increased amount of carboxyl groups (10.5%). This results in a high specific capacitance of 207 F g(-1), a high-rate capability with a capacitance retention of 93%, a high energy density of 24.8-23.1 W h kg(-1), and an excellent cycling durability of up to 3000 cycles. The electrochemical performance improvement can be explained by the combined effect of the high surface area relative to the increased electrical double-layers, the high volume fraction of mesopores relative to shorter diffusion routes and low resistance pathways for ions, and the increased amount of carboxyl groups on the CNF surface relative to enhanced wettability.

Ruthenium and ruthenium oxide nanofiber supports for enhanced activity of platinum electrocatalysts in the methanol oxidation reaction.

Novel supports for the dispersion of Pt electrocatalysts in fuel cells are constantly being developed in order to improve the electrochemical performance and reduce the cost. The electrocatalytic activity and stability in fuel cells largely depend on the surface morphology and structure of the support. In this study, Ru and RuO2 nanofibers prepared by electrospinning and post-calcination have been considered as Pt-catalyst supports. The composite material loaded with 20 wt% Pt catalyst exhibited a high anodic current density of 641.7 mA mgPt(-1), a high IF/IB ratio of 1.9, and excellent electrocatalytic stability compared to commercial Pt/C. The improved anodic current density of the composite is attributed to the high dispersion of the Pt catalyst over the large surface area of the nanosized support grains, while its low onset potential, high IF/IB ratio, and excellent electrocatalytic stability are ascribed to a bifunctional effect resulting from the existence of Ru atoms on the support surface. Finally, the efficient electron transfer and a rapid diffusion rate of the electrolyte are due to the unique network structure of the supports. Thus, the Ru and RuO2 nanofiber composites act as promising Pt-catalyst supports for the methanol oxidation reaction.

A Titanium-Doped SiOx Passivation Layer for Greatly Enhanced Performance of a Hematite-Based Photoelectrochemical System.

This study introduces an in situ fabrication of nanoporous hematite with a Ti-doped SiOx passivation layer for a high-performance water-splitting system. The nanoporous hematite with a Ti-doped SiOx layer (Ti-(SiOx /np-Fe2 O3 )) has a photocurrent density of 2.44 mA cm(-2) at 1.23 VRHE and 3.70 mA cm(-2) at 1.50 VRHE . When a cobalt phosphate co-catalyst was applied to Ti-(SiOx /np-Fe2 O3 ), the photocurrent density reached 3.19 mA cm(-2) at 1.23 VRHE with stability, which shows great potential of the use of the Ti-doped SiOx layer with a synergistic effect of decreased charge recombination, the increased number of active sites, and the reduced hole-diffusion pathway from the hematite to the electrolyte.

Surface modification and characterization of electrosprayed Sn-doped In2O3 thin films.

We synthesized Sn-doped In2O3 (Indium tin oxide, ITO) thin films using electrospray and spin-coating. Scanning electron microscopy, atomic force spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Hall-effect measurement, and UV-vis spectrophotometry measurements were performed to investigate the morphological, structural, chemical, electrical, and optical properties of the electrosprayed ITO films with a sol-layer coating for surface modification. To obtain the optimum performance of the resultant ITO thin films after surface modification, we heat-treated them at four different temperatures of 450 degrees C (sample A), 550 degrees C (sample B), 650 degrees C (sample C), and 750 degrees C (sample D) using microwave heating. Surface modified ITO thin films calcined at 550 degrees C (sample B) using electrospray and spin-coating are observed to have superior resistivity (9.9 x 10(-3) 2 Ω x cm) and optical transmittance (-92.08%) owing to the improved densification of the ITO surface by spin-coating and the formation of uniform ITO thin films by electrospraying.

Correction to "Band Gap and Morphology Engineering of Hematite Nanoflakes from an Ex Situ Sn Doping for Enhanced Photoelectrochemical Water Splitting".

[This corrects the article DOI: 10.1021/acsomega.2c04028.].

Hierarchical metal/semiconductor nanostructure for efficient water splitting.

A hierarchically patterned metal/semiconductor (gold nanoparticles/ZnO nanowires) nanostructure with maximized photon trapping effects is fabricated via interference lithography (IL) for plasmon enhanced photo-electrochemical water splitting in the visible region of light. Compared with unpatterned (plain) gold nanoparticles-coated ZnO NWs (Au NPs/ZnO NWs), the hierarchically patterned Au NPs/ZnO NWs hybrid structures demonstrate higher and wider absorption bands of light leading to increased surface enhanced Raman scattering due to the light trapping effects achieved by the combination of two different nanostructure dimensions; furthermore, pronounced plasmonic enhancement of water splitting is verified in the hierarchically patterned Au NPs/ZnO NWs structures in the visible region. The excellent performance of the hierarchically patterned Au NPs/ZnO NWs indicates that the combination of pre-determined two different dimensions has great potential for application in solar energy conversion, light emitting diodes, as well as SERS substrates and photoelectrodes for water splitting.

Synthesis and characterisation of polygonal indium tin oxide nanocrystals.

Polygon ITO (Sn-doped In2O3) nanocrystals were synthesised via electrospinning, and their morphology, structural properties, and chemical composition were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). To determine the optimum conditions for the fabrication of polygon ITO nanocrystals, calcination temperature after the electrospinning process was controlled at 500 degrees C, 600 degrees C, 700 degrees C, and 800 degrees C, and the amount of PVP polymer was controlled at 4 wt%, 7 wt%, and 10 wt%. For comparison purposes, single In2O3 nanocrystals were also synthesised via electrospinning and calcination. The results show that ITO nanocrystals fabricated at a calcination temperature of 800 degrees C and with 10 wt% of PVP polymer exhibit clear polygon structure with single-crystallinity, which may be explained in terms of the effect of Sn doping in the In2O3 matrix and the oriented aggregation and Oswald ripening growth during the fusion process of ITO nanocrystals.

MOF-Derived Co Nanoparticles Catalyst Assisted by F- and N-Doped Carbon Quantum Dots for Oxygen Reduction.

The oxygen reduction reaction is crucial in the cathode of fuel cells and metal-air batteries. Consequently, designing robust and durable ORR catalysts is vital to developing metal-air batteries and fuel cells. Metal-organic frameworks feature an adjustable structure, a periodic porosity, and a large specific surface area, endowing their derivative materials with a unique structure. In this study, F and N co-doped on the carbon support surface (Co/FN-C) via the pyrolysis of ZIF-67 as a sacrificial template while using Co/FN-C as the non-noble metal catalysts. The Co/FN-C displays excellent long-term durability and electrochemical catalytic performance in acidic solutions. These performance improvements are achieved because the CQDs alleviate the structural collapse during the pyrolysis of ZIF-67, which increases the active sites in the Co nanoparticles. Moreover, F- and N-doping improves the catalytic activity of the carbon support by providing additional electrons and active sites. Furthermore, F anions are redox-stable ligands that exhibit long-term operational stability. Therefore, the well-dispersed Co NPs on the surface of the Co/FN-C are promising as the non-noble metal catalysts for ORR.

Parabens inhibit the early phase of folliculogenesis and steroidogenesis in the ovaries of neonatal rats.

Parabens are widely used as anti-microbial agents in the cosmetic and pharmaceutical industries. Recently, parabens have been shown to act as xenoestrogens, a class of endocrine disruptors. In the present study, 55 female pups were given daily subcutaneous injections of methyl-, propyl-, and butyl-paraben or 17beta-estradiol (E2) during neonatal Day 1-7. The ovaries were excised on postnatal Day 8, then fixed and stained with hematoxylin and eosin for histological analysis. The follicles were counted and classified as being in the primordial, early primary, or primary stages. The number of primordial follicles increased while early primary follicles decreased at the high doses of propyl- and butyl-paraben. The levels of anti-Mullerian hormone (AMH) and Foxl2 mRNA increased by propyl- and butyl-parabens whereas kit ligand/stem cell factor (KITL) expression was up regulated only by butyl-paraben. The mRNA levels of StAR and Cyp11a1 were significantly decreased after treatment with methyl-, propyl-, and butyl-parabens. Consistent with its use as a positive control, E2 regulated the expression of KITL, StAR, and Cyp11a1 genes, but surprisingly did not affect AMH and Foxl2 levels. Thus, E2 and parabens had different effects on the regulation of folliculogenic and steroidogenic genes, demonstrating the estrogenic and nonestrogenic properties of parabens in the ovary. Taken together, our data show that parabens stimulated AMH mRNA expression and consequently inhibited the early phase of folliculogenesis in the ovaries of neonatal female rat. The levels of steroidogenic enzymes, indicators of follicle differentiation, appeared to be regulated by parabens through inhibition of their transcriptional repressor, Foxl2.

Three-dimensional nano-foam of few-layer graphene grown by CVD for DSSC.

We report a robust and direct route to fabricate a three-dimensional nano-foam of few-layer graphene (3D-NFG) with large area coverage via a chemical vapor deposition (CVD) technique. Pyrolysis of polymer/nickel precursor film under a hydrogen environment, simply prepared by spin-coating, leads to the creation of nano-foam in the film and the reduction process of nickel ions. Carbonized-C and the nickel nano-frame formed from the pyrolysis are used as a solid carbon source and as a catalyst for the growth of graphene under CVD conditions, respectively. We investigate the use of 3D-NFG, with the advantage of large surface area and high conductivity, as an alternative to the Pt counter electrode material in dye sensitized solar cells. The excellent properties of 3D-NFG, fabricated in this simple and direct manner, suggest a great potential for interconnected graphene networks in electronic devices and photocatalytic sensors as well as in energy-related materials.

Fabrication and photovoltaic properties of heterostructured TiO2 nanowires.

One-dimensional heterostructured TiO2 nanowires were successfully fabricated by an electrospinning technique and modified by hydrolysis. We investigated their structure, morphology, chemical composition, and optical properties by using the X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. In the case of the photovoltaic performance, the short-circuit current density and cell efficiency of the DSSCs employing single TiO2 nanowires and heterostructured TiO2 nanowires improve from 6.90 to 11.38 mA/cm2 and from 2.56 to 4.29%, respectively. The results show that the photoconversion efficiency of the heterostructured TiO2 nanowires could be improved by more than approximately 67% compared to that of the single TiO2 nanowires because of the enhanced specific surface area that facilitates dye adsorption.

Band gap and Morphology Engineering of Hematite Nanoflakes from an Ex Situ Sn Doping for Enhanced Photoelectrochemical Water Splitting.

In this article, we report a simple ex situ Sn-doping method on hematite nanoflakes (coded as MSnO2-H) that can protect the nanoflake (NF) morphology against the 800 °C high-temperature annealing process and activate the photoresponse of hematite until 800 nm wavelength excitation. MSnO2-H has been fabricated by dropping SnCl4 ethanol solution on hematite nanoflakes homogeneously grown over the conductive FTO glass substrate and annealed at 500 °C to synthesize the SnO2 nanoparticles on hematite NFs. The Sn-treated samples were then placed in a furnace again, and the sintering process was conducted at 800 °C for 15 min. During this step, structure deformation of hematite occurs normally due to the grain boundary motion and oriented attachment. However, in the case of MSnO2-H, the outer SnO2 nanoparticles efficiently prevented a shape deformation and maintained the nanoflake shape owing to the encapsulation of hematite NFs. Furthermore, the interface of hematite/SnO2 nanoparticles became the spots for a heavy Sn ion doping. We demonstrated the generation of the newly localized states, resulting in an extension of the photoresponse of hematite until 800 nm wavelength light irradiation. Furthermore, we demonstrated that SnO2 nanoparticles can effectively act as a passivation layer, which can reduce the onset potential of hematite for water splitting redox reactions. The optimized MSnO2-H nanostructures showed a 2.84 times higher photocurrent density and 300 mV reduced onset potential compared with a pristine hematite nanoflake photoanode.

Well-dispersed Pt/RuO2-decorated mesoporous N-doped carbon as a hybrid electrocatalyst for Li-O2 batteries.

Despite their high energy density, the poor cycling performance of lithium-oxygen (Li-O2) batteries limits their practical application. Therefore, to improve cycling performance, considerable attention has been paid to the development of an efficient electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Catalysts that can more effectively reduce the overpotential and improve the cycling performance for the OER during charging are of particular interest. In this study, porous carbon derived from protein-based tofu was investigated as a catalyst support for the oxygen electrode (O2-electrode) of Li-O2 batteries, wherein ORR and OER occur. The porous carbon was synthesized using carbonization and KOH activation, and RuO2 and Pt electrocatalysts were introduced to improve the electrical conductivity and catalytic performance. The well-dispersed Pt/RuO2 electrocatalysts on the porous N-doped carbon support (Pt/RuO2@ACT) showed excellent ORR and OER catalytic activity. When incorporated into a Li-O2 battery, the Pt/RuO2@ACT O2-electrode exhibited a high specific discharge capacity (5724.1 mA h g-1 at 100 mA g-1), a low discharge-charge voltage gap (0.64 V at 2000 mA h g-1), and excellent cycling stability (43 cycles with a limit capacity of 1000 mA h g-1). We believe that the excellent performance of the Pt/RuO2@ACT electrocatalyst is promising for accelerating the commercialization of Li-O2 batteries.

Structural and electrochemical properties of Ag nano-dots combined amorphous Si electrodes for thin-film lithium rechargeable batteries.

We have one-pot fabricated Si-based nanocomposite electrodes containing Ag nano-dots for thin-film Li rechargeable batteries by a co-sputtering method. The structural and electrochemical properties of the Si/Ag nanocomposite electrodes are investigated via transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cycler. The TEM and XRD results show that crystalline Ag nano-dots (approximately 5-9 in size) are well-dispersed within an amorpohous Si matrix. It is shown that the Si/Ag nanocomposite electrode shows much better structural stability than the Si only sample. It is also shown that the Si/Ag nanocomposite electrode shows superior capacity retention compared to the Si only electrode. The results indicate that the presence of the Ag nano-dots is important minimizing the formation of cracks in the electrode, so leading to the better life-time for thin-film Li rechargeable batteries.

Interfacial Engineering of a Heteroatom-Doped Graphene Layer on Patterned Aluminum Foil for Ultrafast Lithium Storage Kinetics.

The design of the interfacial architecture between the electrode and the current collector in lithium-ion batteries (LIB) plays a key role in achieving ultrafast lithium storage kinetics with respect to efficient charge transfer and cycle stability. However, in recent years, despite considerable efforts in the structural and chemical engineering of active materials (anode and cathode materials), interfacial architectures between the electrode and the current collector have received relatively insufficient attention in the case of ultrafast LIBs. Here, the interface architecture of a micropatterned Al current collector with a heteroatom-doped graphene interfacial layer is developed using roll pressing and dip coating processes. The cathode electrode fabricated with the resultant current collector offers increased contact area with enhanced interfacial stability between the electrode and the current collector because of micropatterns with heteroatom-doped graphene formed on the current collector, leading to outstanding ultrafast cycling capacity (105.8 mA h g-1) at 20 C. Furthermore, at extremely high rate and long-term cycling performance, significant ultrafast cycling stability (specific capacity of 87.1 mA h g-1 with capacity retention of 82.3% at 20 C after 1000 cycles) is noted. These improved ultrafast and ultra-stable performances are explained in terms of the increased electron collection/provision site with a high contact area between the electrode and the current collector for enhanced ultrafast cycling capacity and the effective corrosion prevention of the current collector with fast charge transfer for ultrafast cycling stability.

Novel tunneled phosphorus-doped WO3 films achieved using ignited red phosphorus for stable and fast switching electrochromic performances.

Simultaneous improvement of both the performance and stability of electrochromic devices (ECDs) to encourage their practical use in various applications, such as commercialized smart windows, electronic displays, and adjustable mirrors, by tuning the film structure and the electronic structure of transition metal oxides remains a challenging issue. In the present study, we developed novel tunneled phosphorus (P)-doped WO3 films via the ignition reaction of red P. The ignited red P, which can generate exothermic energy, was used as an attractive factor to create a tunneled structure and P-doping on the WO3 films. Therefore, by optimizing the effect of ignited red P on the WO3 films, tunneled P-doped WO3 films fabricated by using 1 wt% red P demonstrated a striking improvement of the EC performances, including both a fast switching speed (6.1 s for the colouration speed and 2.5 s for the bleaching speed) caused by the improvement of Li ion diffusion by the tunneled structure and electrical conductivity by P-doping WO3 and a superb colouration efficiency (CE, 55.9 cm2 C-1) as a result of increased electrochemical activity by the elaborate formation of the tunneled structure. Simultaneously, this film displayed a noticeable long-cycling stability due to a higher retention (91.5%) of transmittance modulation after 1000 electrochromic (EC) cycles as compared to bare WO3 films, which can mainly be attributed to the optimizing effect of the tunneled structure to generate an efficient charge transfer and an alleviated structural variation during the insertion-extraction of Li ions. Therefore, our results suggest a valuable and well-designed strategy to manufacture stable fast-switching EC materials that are fit for various practical applications of the ECDs.

Effects of Trauma Center Establishment on the Clinical Characteristics and Outcomes of Patients with Traumatic Brain Injury : A Retrospective Analysis from a Single Trauma Center in Korea.

OBJECTIVE: To investigate the effects of trauma center establishment on the clinical characteristics and outcomes of trauma patients with traumatic brain injury (TBI). METHODS: We enrolled 322 patients with severe trauma and TBI from January 2015 to December 2016. Clinical factors, indexes, and outcomes were compared before and after trauma center establishment (September 2015). The outcome was the Glasgow outcome scale classification at 3 months post-trauma. RESULTS: Of the 322 patients, 120 (37.3%) and 202 (62.7%) were admitted before and after trauma center establishment, respectively. The two groups were significantly different in age (p=0.038), the trauma location within the city (p=0.010), the proportion of intensive care unit (ICU) admissions (p=0.001), and the emergency room stay time (p<0.001). Mortality occurred in 37 patients (11.5%). Although the preventable death rate decreased from before to after center establishment (23.1% vs. 12.5%), the difference was not significant. None of the clinical factors, indexes, or outcomes were different from before to after center establishment for patients with severe TBI (Glasgow coma scale score ≤8). However, the proportion of inter-hospital transfers increased and the time to emergency room arrival was longer in both the entire cohort and patients with severe TBI after versus before trauma center establishment. CONCLUSION: We confirmed that for patients with severe trauma and TBI, establishing a trauma center increased the proportion of ICU admissions and decreased the emergency room stay time and preventable death rate. However, management strategies for handling the high proportion of inter-hospital transfers and long times to emergency room arrival will be necessary.

Patterned array of nanoparticles on substrates via contact printing method with CNTs/AAO stamp.

Patterned arrays of Fe oxide nanoparticles were transferred via contact printing method on a substrate surface using carbon nanotubes embedded in anodic aluminum oxide (CNTs/AAO) as a stamp, in which vertically aligned CNTs in hexagonally patterned array was first fabricated by chemical vapor deposition into the AAO, followed by a partial chemical etching to expose the CNTs from the AAO. Fe precursor inked CNTs stamp was contact-printed on a Pt-coated Si substrate, and after heat treatment at 200 degrees C, patterned array of Fe oxide nanoparticles with ca. 80 nm of diameter and ca. 120 nm of inter-distance between the nanoparticles was consequently obtained.