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Several methods and catalysts have been investigated for eco-friendly ammonia (NH3) production under mild conditions in the past few decades. NH3 is important chemical fertilizer and now expecting as H2 carrier, and mainly synthesized by Haber-Bosch process under severe conditions (400 ℃, 20MPa). In contrast, nitrogenases, biocatalyst can activate N2 and H2O to form NH3 under ambient conditions in nature with a low synthesis rate. Herein we first reported photobiocatalytic NH3 production by the combination of cyanobacterial Anabaena variabilis as a whole-cell biocatalyst coupled with TiO2 as a photocatalyst in the existence of glycerol as a sacrificial reagent and viologens as an electron transfer mediator. Comparing with natural system, the formation rate of NH3 from a combination with inorganic photocatalyst was much increased by ca. 20.86 times. Biocatalytic reactions revealed that only reduced MV•+ passed into whole cells and transfer electrons to nitrogenase efficiently for NH3 production. The amount of intracellular [MoFe]-nitrogenase was increased in cyanobacteria cultivated in a nitrogen-deficient Allen & Arnon medium. The complete hybrid system produced NH3 with a maximum rate of 3.3 µM·g-1·h-1. This study is the first demonstration of the sustainable technology for solar-to-NH3 conversion as an energy carrier for a future carbon-neutral energy society.

Intentionally introducing tensile strain into TiO2 by using a spark plasma sintering process could stabilize reduced Ti species and improve the solid acid activity for acetalization.

CO$_2$ photoreduction on photocatalysts is a nature-friendly solution to decrease the CO$_2$ amount, but the method still has low efficiency because of difficult separation and easy recombination of charge carriers in available catalysts. In this study, a high-entropy oxynitride was introduced as an active photocatalyst for photoreduction. The material had a chemical composition of TiZrNbHfTaO$_6$N$_3$ and was produced by a high-pressure torsion method followed by oxidation and nitriding. It showed higher photocatalytic CO$_2$ to CO conversion compared to corresponding high-entropy oxide, benchmark photocatalyst P25 TiO$_2$, and almost all catalysts introduced in the literature. The high activity of this oxynitride, which also showed good chemical stability, was attributed to the large absorbance of light and easy separation of electrons and holes, the low recombination of charge carriers, and the high CO$_2$ adsorption on the surface. These findings introduce high-entropy oxynitrides as promising photocatalysts for CO$_2$ photoreduction.

The solvated structure of a highly concentrated hybrid tetraglyme (G4)-water electrolyte was studied for an increasing cycle stability and performance of a KS6 used dual-ion battery. Hybrid solvent of G4 and water with a weight ratio of 2 to 8 was able to dissolve 9LiFSI-1LiTFSI supporting salts up to 37 mol kg

Charge-discharge performance at −30 °C was studied by using low-viscosity ester solvents (propyl acetate (PA), propyl propionate (PP), and ethyl propionate (EP)) as electrolyte for improving the lo...

A high-concentration aqueous electrolyte with a wide electrochemical stability window represents a novel development direction for traditional aqueous batteries. Herein, a novel high-concentration water-in-bisalt electrolyte using LiFSI (lithium bis(fluorosulfonyl)imide) and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) as supporting salts was first applied as an electrolyte of a dual-ion battery, and the solvated structure changes were studied in detail. Electronic interactions were detected between the two supporting salts. Furthermore, when 37 mol/kg LiFSI-LiTFSI/H2O was applied to a 3 V dual-ion battery, by using graphitic carbon (KS6) and activated carbon (AC) as cathode and anode materials, the full cell delivered a high specific capacity of 72 mAh/g. In addition, excellent cycling stability for ˃100 cycles was achieved with negligible capacity fading.

Metal oxynitrides are promising photocatalysts due to their narrow bandgap, but their lower stability compared to metal oxides is a drawback. The introduction of high-entropy alloys with entropy-stabilization features has shown high potential for various functional applications in recent years. By considering these two types of materials, we developed a high-entropy oxynitride for photocatalytic water splitting. The material, with a general composition of TiZrHfNbTaO6N3 and a d0 electronic configuration, showed a narrow bandgap of 1.6 eV, which is much lower than the bandgaps of relevant binary and high-entropy oxides. The material exhibited photocurrent generation and photocatalytic hydrogen production with high chemical stability, suggesting the high potential of high-entropy oxynitrides as advanced low-bandgap and stable photocatalysts.

Novel donor-acceptor dyads containing [2.2]- and [3.3]paracyclophane (PCP) as the bridging moiety were synthesized and used to effectively fabricate dye-sensitized hydrogen production systems. All the prepared compounds had a phenothiazine and a cyanoacrylic acid/pyridinyl acrylonitrile moiety acting as an electron donor and acceptor, respectively. Although cyclic voltammetry measurements showed similar electron-donating properties among all the synthesized dyads, the lowest absorption energy of the [2.2]PCP moiety was lower than that of the [3.3]PCP one; this was due to its shorter distance between benzene rings, which could effectively drive the charge transfer between the donor and acceptor chromophores. Under visible light (395 nm), a dyad-loaded photocatalyst in a 0.5 M aqueous glycerol solution generated detectable hydrogen gases. The optimal turnover number and photocurrent order exhibited the same trend as the hydrogen production rate since the suggested number of excited photons played a critical role in hydrogen production.

Bismuth oxide (Bi2O3), a yellow semiconductor ceramic, is considered as an advanced photoactive energy material, but its activity still needs further improvement for practical applications. In this study, black Bi2O3 with nanocrystalline structure and large fraction of oxygen vacancies is synthesized by mechanical straining via the high-pressure torsion (HPT) method. The black oxide exhibits enhanced light absorbance under both UV and visible lights. It shows a bipolar photocurrent behavior with up to six times higher photocurrent density compared with the unprocessed yellow Bi2O3. This study shows the high potential of severely-strained black Bi2O3 for photovoltaic, photoconductivity and photocatalytic applications.

Titanium oxide (TiO2), with the anatase and rutile structures, has been widely studied for photovoltaic and solar cell applications, but its main drawback is large bandgap, which limits its activit...

Oxynitrides are considered as new potential candidates for photocatalysis due to their lower bandgap compared with traditional oxide photocatalysts. However, the formation of native nitrogen monovacancies during the synthesis of oxynitrides reduces their photocatalytic activity due to the vacancy-induced electron/hole recombination. This study shows that a transition from the native nitrogen monovacancies to the nitrogen-based vacancy complexes in a GaN–ZnO oxynitride not only diminishes the recombination but also enhances the photocatalytic hydrogen production. Here, the vacancy complexes are introduced by mechanical straining via the high-pressure torsion (HPT) method and it is shown that the vacancy complexes reduce the bandgap and increase the over-potential for hydrogen production on the conduction band. The current results introduce a simple but effective approach to turn the nitrogen vacancies to favorable defects for photocatalysis.

Stable photoelectrochemical (PEC) operation is a critical issue for the commercialization of PEC water-splitting systems. Unfortunately, most semiconductor photocathodes generating hydrogen in these systems are unstable in aqueous solutions. This is a huge limitation for the development of durable PEC water-splitting systems. Lanthanum iron oxide (LaFeO3) is a promising p-type semiconductor to overcome this drawback because of its stability in an aqueous solution and its proper energy level for reducing water. In this study, we fabricated a crystalline LaFeO3 thin film by radio frequency magnetron sputtering deposition and a post-annealing process in air for use as a PEC photocathode. Based on the morphological, compositional, optical and electronic characterizations, we found that it was ideal for a visible light-responsive PEC photocathode and tandem PEC water-splitting system with a small band gap absorber behind it. Furthermore, it showed stable PEC performance in a strong alkaline solution during PEC operation without any protection layers. Therefore, the crystalline sputtered LaFeO3 thin film suggested in this study would be feasible to apply as a PEC photocathode for durable, simple and low-cost PEC water splitting.

Photocatalytic water splitting is the most ideal system to harvest solar energy for the production of useful chemicals. There have been many attempts to increase the photocatalytic activity of the TiO2 photocatalyst, such as loading co-catalysts and dopants, and the introduction of oxygen vacancies. Strain effects have also attracted much interest to increase the charge mobility in bulk oxide. Here, we report on the effectiveness of tensile strain in stabilizing the anatase phase of TiO2 at high temperature and increasing the photocatalytic activity by an increase in the charge separation with a unique mixed phase structure. The rate of H2 formation over TiO2 was decreased upon spark plasma sintering (SPS) treatment because of a decrease in the surface area; however, SPS treatment with Au dispersion significantly increased the H2 formation rate to higher than that over commercially available P-25 TiO2 (no SPS treatment) loaded with Au. The O2 formation rate was also increased by strain effects in TiO2. Furthermore, strain effects were effective for visible light sensitivity on TiO2.

The need for sustainable, renewable and low-cost approaches is a driving force behind the development of solar-to-H2 conversion technologies. This study aims to develop a new strategy using a visible-light photocatalyst coupled to a biocatalyst for H2 production. Photocatalytic methyl viologen (MV2+) reduction activity was investigated to discover active oxynitrides. In comparative studies with LaTiO2N, BaTaO2N and Ta3N5, it was revealed that the suitable surface area, band gap and band edge potentials are some physical factors that are responsible for the photocatalytic behaviors of GaN:ZnO in MV2+ reduction. The activity is enhanced at higher concentrations and the alkaline pH of triethanolamine (TEOA). The expression of an active [FeFe]-hydrogenase from Escherichia coli (Hyd+E. coli) as a recombinant biocatalyst was confirmed by its MV˙+-dependent H2 production activity. In the photobiocatalytic system of GaN:ZnO and Hyd+E. coli, the rate of H2 production reached the maximum level in the presence of MV2+ as an electron mediator at neutral pH as a biocompatible condition. The present work reveals a novel hybrid system for H2 production using visible-light active GaN:ZnO coupled to Hyd+E. coli, which shows the feasibility of being developed for photobiocatalytic H2 evolution under solar light.

Photocatalysis on semiconductors using solar energy sources provides a clean technology to produce hydrogen from water splitting. Although zirconia (ZrO2) is a semiconductor oxide, it is not generally considered as a photocatalyst owing to its poor light absorbance and wide bandgap (over 5 eV). In this study, black ZrO2 with a large concentration of lattice defects such as oxygen vacancies, dislocations and nanograin boundaries is stabilized by high-pressure torsion (HPT) straining. The black ZrO2, which experiences monoclinic–tetragonal phase transformations during the HPT process, shows large light absorption, a small bandgap, reduced conduction band energy and high photocatalytic activity for hydrogen evolution due the presence of oxygen vacancies. These results confirm that the introduction of strain-induced oxygen vacancies is a potential method to produce low-bandgap photocatalysts.

The direct decomposition of nitrogen oxides (NOX) is an ideal way to remove NOX pollution created by chemical industries and automobiles. Ba3Y4O9 is a promising candidate for the NOX direct decomposition reaction, however, its catalytic activity is not high enough and the stability is insufficient. Here, NO decomposition activity on several metal ion doped Ba3Y4O9 catalysts is reported and it is found that Cu is the most effective for increasing the activity. With 10% Cu doping, the catalytic activity and the stability were improved simultaneously. Temperature programmed desorption (TPD) results indicate that doping with Cu increased the amount of surface oxygen vacancies and mobility of the lattice oxygen resulting in an increase of NO adsorption and the promotion of the decomposition of NOX intermediate species. In situ FT-IR spectra prove that Cu doping weakened the association of NO3− species, thus promoting the decomposition of NO3− species at low temperatures, which resulted in high catalytic activity for NOX decomposition. These results indicate that introducing Cu into the Ba3Y4O9 system is an effective way to achieve high activity and a stable catalyst for the direct decomposition of NOX.

Water-acetonitrile (AN) hybrid electrolyte with high concentration of bis(trifluoromethanesulfonyl) imide (LiTFSI) and Lithium bis(fluorosulfonyl) imide (LiFSI) (LiTFSI-LiFSI=3:1, molar ratio) supporting salts are studied for the high potential and large capacity rechargeable dual-ion battery. Water-acetonitrile hybrid electrolyte (WA) shows a wide electrochemical stability window of 3.1 V in 20 m aqueous electrolyte and 3.6 V in 20 m 9LiFSI-1LiTFSI in water: AN=1:3 molar ratio electrolyte. In particular, high oxidation potential, which can be assigned to the strong solvated ionic cluster formed between AN, water and LiTFSI-LiFSI supporting salts. The dual-ion battery is assembled using the graphitic carbon (KS6) and the activated carbon (AC) as cathode and anode, respectively, and 20 m LiTFSI-LiFSI in hybrid AN-water as electrolyte. It is found that the reasonably large capacity, coulombic efficiency and cycle stability were achieved. The KS6/AC cell shows 86 mAh g−1 at the initial cycle and 50 mAh g−1 at 100th cycle in a voltage range of 0–3.25 V, and the average coulombic efficiency of 85% is sustained over 200 cycles. The solvated structure of water to Li+ is strengthened by addition of AN from ATR-IR and NMR spectrums analysis and this change in the solvated structure is the main reason for the increased performance of the aqueous dual-ion battery.

Solar water splitting to produce hydrogen is a promising solution for global energy issues. One of the main bottlenecks in this technology is the spontaneous fast backward reaction (2H2 + O2 → H2O,...

Novel perfluoroalkyl gelators without hydrogen bonds–bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) isophthalate (1m), bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) terephthalate...

The synthesis, structure, physical properties, and electrocatalytic hydrogen production of tetrathiatetracene ligand based [FeFe]-hydrogenase mimic molecules were investigated. By adjusting the amount of iron, mono- and bis-[FeFe] coordinated complexes 1 and 2 were synthesized. The structures of 1 and 2 were analysed by NMR, IR, and absorption spectroscopies, and cyclic voltammetry and DFT computational analysis. In the DFT electron density maps, the HOMOs and LUMOs were located at tetrathiatetracene units, indicating that these complexes retain mainly acene characteristics. When weak acid Et3NHBF4 was added to CH2Cl2 solutions of 1 or 2, the reduction potential of iron complexes was shifted to more positive values proportional to the concentration of acid. As the acid concentration increased, the current of the reduction wave also increased, indicating the occurrence of a catalytic proton reduction reaction. The bulk electrolysis reaction showed 65.8 TON for 1 and 52.8 TON for 2.

The unique frictional behavior of polyethylenimine/molybdenum disulphide (PEI/MoS2)n thin films on steel substrates, deposited via the layer-by-layer (LbL) technique, is explored. The effects of gaseous atmosphere (i.e. air vs. dry nitrogen), and heat treatment of the coatings are investigated. The coefficients of friction (COFs) are reduced by factors of ca. 2 and 11 in air and N2 respectively, compared to an uncoated steel substrate. Ultra-low friction (COF

Heptacene (1) has been produced via a monoketone precursor, 2, which was prepared from 1,2,4,5-tetrabromobenzene in nine steps in a total yield of 10 %. Compound 2 was converted to 1 quantitatively by heating at 202 °C. Heptacene exhibited high thermal stability in the solid state without any observable change over two months. To investigate the potential value of 1 as a material for p-type organic field-effect transistors (OFETs), top-contact OFET devices were fabricated by vacuum deposition of 1 onto a hexamethyldisilazane (HMDS)/SiO2 /Si substrate. The best hole mobility performance was 2.2 cm2 V-1 s-1 . This is the first report of stable heptacene being used in an effective device and examined for its charge carrier properties.

Heptacene (1) has been produced via a monoketone precursor, 2, which was prepared from 1,2,4,5-tetrabromobenzene in nine steps in a total yield of 10 %. Compound 2 was converted to 1 quantitatively by heating at 202 °C. Heptacene exhibited high thermal stability in the solid state without any observable change over two months. To investigate the potential value of 1 as a material for p-type organic field-effect transistors (OFETs), top-contact OFET devices were fabricated by vacuum deposition of 1 onto a hexamethyldisilazane (HMDS)/SiO

An inorganic-biological hybrid system that integrates features of both stable and efficient semiconductors and selective and efficient enzymes is attractive for facilitating the conversion of solar energy to hydrogen. In this study, we aimed to develop a new photocatalytic hydrogen-production system based on Escherichia coli whole-cell genetically engineered as a biocatalysis for highly active hydrogen formation. The photocatalysis part was obtained by bacterial precipitation of cadmium sulfide (CdS), which is a visible-light-responsive semiconductor. The recombinant E. coli cells were sequentially subjected to CdS precipitation and heterologous [FeFe]-hydrogenase synthesis to yield a CdS@E. coli hybrid capable of light energy conversion and hydrogen formation in a single cell. The CdS@E. coli hybrid achieved photocatalytic hydrogen production with a sacrificial electron donor, thus demonstrating the feasibility of our system and expanding the current knowledge of photosensitization using a whole-cell biocatalyst with a bacterially precipitated semiconductor.