Heterostructure engineering and ultralow Pt-loaded multicomponent nanocage for efficient electrocatalytic oxygen evolution.

Developing highly efficient electrocatalysts based on appropriate heterojunction engineering and electronic structure modification for the oxygen evolution reaction (OER) has been extensively recognized as an effective approach to increase the efficiency of water splitting. Herein, ultralow Pt-loaded (1 %) NiCoFeP@NiCoFe-PBA hollow nanocages with well-defined heterointerfaces and modified electronic environment are successfully fabricated. As expected, the obtained Pt-NiCoFeP@NiCoFe-PBA exhibits outstanding performance with a low overpotential of 255 mV at 10 mA cm-2 and a small Tafel slope of 57.2 mV dec-1. More specifically, the highly open three-dimensional structure, exquisite interior voids and abundant surface defects endow Pt-NiCoFeP@NiCoFe-PBA nanocages with more electrochemical active sites. Meanwhile, experimental results and mechanism studies also reveal that the construction of heterogeneous interfaces as well as incorporation of noble metals could readily induce strong synergistic effects and significantly tailor electronic configurations to optimize the binding energy of the intermediates, thereby achieving prominent OER performance.

Photoelectrocatalytic oxidation of ethylene glycol on trimetallic PdAgCu nanospheres enhanced by surface plasmon resonance.

The notable surface plasmon resonance (SPR) effect of some metals has been applied to improve the efficiency of alcohol oxidation reactions, whereas the comprehensive investigation of Cu-assisted photoelectrocatalysis remains challenging. We herein successfully prepared trimetallic PdAgCu nanospheres (NSs) with abundant surface bulges for the advanced ethylene glycol oxidation reaction (EGOR) and compared them with bimetallic PdAg NSs to investigate the performance enhancement mechanism. Impressively, the as-optimized PdAgCu NSs exhibited superb mass activity and electrochemical stability. Moreover, under visible light illumination, the mass activity of PdAgCu NSs increased to 1.62 times compared to that in the dark, and in contrast, the mass activity of PdAg NSs only increased to 1.48 times that in the dark. A mechanistic study indicated that the incorporation of Cu not only strengthens the whole SPR effect of PdAgCu NSs but also further modifies the electronic structure of Pd. This work highlighted that the incorporation of Cu into PdAg NSs further enhanced the photoelectrocatalytic performance and increased noble metal atom utilization, which may provide guidance to fabricate novel and promising nanocatalysts in the field of photoelectrocatalysis.

In situ nanopores enrichment of Mesh-like palladium nanoplates for bifunctional fuel cell reactions: A joint etching strategy.

Two-dimensional (2D) nanomaterials with nanopore display an enhancement effect on electrocatalysis behavior, whereas the nanopore engineering for 2D nanocatalysts remains an insurmountable challenge. We advance the synthesis of multilayer Pd nanoplates (Pd NPs) and two types of meshy nanoplates (Pd LMNPs/MNPs) with escalating nanopores from none and sparse to porous. Specially, an in situ nanopore enrichment on these Pd nanoplates hinges on a joint etching strategy with integrated manipulation of reaction kinetics. The optimized Pd MNPs exhibit exceptional oxygen reduction reaction performance, owing to the enhanced intermediates protonation on Pd site neighboring nanopore, which has been elucidated by density functional theory calculations. In addition, Pd MNPs also deliver excellent performances in fuel cell anodic reactions, including ethanol oxidation reaction and formic acid oxidation reaction. This study highlights a new strategy for in situ nanopores engineering, providing a prospect for designing superior nanocatalysts.

Characterizing the degeneration of nuclear membrane and mitochondria of adipose-derived mesenchymal stem cells from patients with type II diabetes.

Regenerative therapeutic approaches involving the transplantation of stem cells differentiated into insulin-producing cells are being studied in patients with rapidly progressing severe diabetes. Adipose-derived mesenchymal stem cells have been reported to have varied cellular characteristics depending on the biological environment of the location from which they were harvested. However, the characteristics of mesenchymal stem cells in type II diabetes have not been clarified. In this study, we observed the organelles of mesenchymal stem cells from patients with type II diabetes under a transmission electron microscope to determine the structure of stem cells in type II diabetes. Transmission electron microscopic observation of mesenchymal stem cells from healthy volunteers (N-ADSC) and those from patients with type II diabetes (T2DM-ADSC) revealed enlarged nuclei and degenerated mitochondrial cristae in T2DM-ADSCs. Moreover, T2DM-ADSCs were shown to exhibit a lower expression of Emerin, a constituent protein of the nuclear membrane, and a decreased level of mitochondrial enzyme activity. In this study, we successfully demonstrated the altered structure of nuclear membrane and the decreased mitochondrial enzyme activity in adipose-derived mesenchymal cells from patients with type II diabetes. These findings have contributed to the understanding of type II diabetes-associated changes in mesenchymal stem cells used for regenerative therapy.

Bulk tungsten-substituted vanadium oxide for low-temperature NOx removal in the presence of water.

NH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100-150 °C) and in the presence of water (~20 vol%). The 3.5 mol% W-substituted vanadium oxide shows >99% (dry) and ~93% (wet, 5-20 vol% water) NO conversion at 150 °C (250 ppm NO, 250 ppm NH3, 4% O2, SV = 40000 mL h-1 gcat-1). Lewis acid sites of W-substituted vanadium oxide are converted to Brønsted acid sites under a wet condition while the distribution of Brønsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on Brønsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 °C. The high redox ability and reactivity of Brønsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor.

Electrochemical hydrogenation of non-aromatic carboxylic acid derivatives as a sustainable synthesis process: from catalyst design to device construction.

Electrochemical hydrogenation of a carboxylic acid using water as a hydrogen source is an environmentally friendly synthetic process for upgrading bio-based chemicals. We systematically studied electrochemical hydrogenation of non-aromatic carboxylic acid derivatives on anatase TiO2 by a combination of experimental analyses and density functional theory calculations, which for the first time shed light on mechanistic insights for the electrochemical hydrogenation of carboxylic acids. Development of a substrate permeable TiO2 cathode enabled construction of a flow-type electrolyser, i.e., a so-called polymer electrode alcohol synthesis cell (PEAEC) for the continuous synthesis of an alcoholic compound from a carboxylic acid. We demonstrated the highly efficient and selective conversion of oxalic acid to produce glycolic acid, which can be regarded as direct electric power storage into an easily treatable alcoholic compound.

A zeolitic vanadotungstate family with structural diversity and ultrahigh porosity for catalysis.

Design of the structure and composition of crystalline microporous inorganic oxides is of great importance in catalysis. Developing new zeolites is one approach towards this design because of the tunable pore system and high thermal stability. Zeolites are limited to main group elements, which limits their applications in redox catalysis. Another promising choice is zeolitic transition metal oxides providing both porosity and redox activity, thereby further expanding the diversity of porous materials. However, the examples of zeolitic transition metal oxides are rare. Here, we report a new class of zeolitic vanadotungstates with tunable frameworks exhibiting a large porosity and redox activity. The assembly of [W4O16]8- units with VO2+ forms two isomeric porous frameworks. Owing to the complex redox properties and open porosity, the vanadotungstates efficiently catalyse the selective reduction of NO by NH3. This finding provides an opportunity for design and synthesis of inorganic multifunctional materials for future catalytic applications.

Carbon-neutral energy cycles using alcohols.

We demonstrated carbon-neutral (CN) energy circulation using glycolic acid (GC)/oxalic acid (OX) redox couple. Here, we report fundamental studies on both catalyst search for power generation process, i.e. GC oxidation, and elemental steps for fuel generation process, i.e. OX reduction, in CN cycle. The catalytic activity test on various transition metals revealed that Rh, Pd, Ir, and Pt have preferable features as a catalyst for electrochemical oxidation of GC. A carbon-supported Pt catalyst in alkaline conditions exhibited higher activity, durability, and product selectivity for electrooxidation of GC rather than those in acidic media. The kinetic study on OX reduction clearly indicated that OX reduction undergoes successive two-electron reductions to form GC. Furthermore, application of TiO2 catalysts with large specific area for electrochemical reduction of OX facilitates the selective formation of GC.

Electrochemical Production of Glycolic Acid from Oxalic Acid Using a Polymer Electrolyte Alcohol Electrosynthesis Cell Containing a Porous TiO2 Catalyst.

A liquid flow-type electrolyser that continuously produces an alcohol from a carboxylic acid was constructed by employing a polymer electrolyte, named a polymer electrolyte alcohol electrosynthesis cell (PEAEC). Glycolic acid (GC, an alcoholic compound) is generated on anatase TiO2 catalysts via four-electron reduction of oxalic acid (OX, a divalent carboxylic acid), accompanied with water oxidation, which achieves continuous electric power storage in easily stored GC. Porous anatase TiO2 directly grown on Ti mesh (TiO2/Ti-M) or Ti felt (TiO2/Ti-F) was newly fabricated as a cathode having favourable substrate diffusivity. A membrane-electrode assembly composed of the TiO2/Ti-M, Nafion 117, and an IrO2 supported on a gas-diffusion carbon electrode (IrO2/C) was applied to the PEAEC. We achieved a maximum energy conversion efficiency of 49.6% and a continuous 99.8% conversion of 1 M OX, which is an almost saturated aqueous solution at room temperature.

Control of dual stimuli-responsive vesicle formation in aqueous solutions of single-tailed ferrocenyl surfactant by varying pH and redox conditions.

This paper reports a method to control the formation and disruption of vesicles from a novel single-tailed surfactant (11-ferrocenylundecylammonium bromide, 11-FAB), which contains two stimuli-responsive groups corresponding to pH variation and redox reaction conditions, by external stimuli. Although 11-FAB is a single-tailed surfactant, pure 11-FAB spontaneously forms vesicles in water. Microscopic observations of 2.5 mM aqueous solutions of pure 11-FAB (pH = 5.2) show that a number of 11-FAB vesicles are giant, with diameters of 10-30 µm. The disruption of vesicles is observed in aqueous 11-FAB solutions under basic conditions. The vesicles are then reformed under acidic conditions. Reduced 11-FAB also forms large vesicles in electrolyte solutions. These vesicles are disrupted by electrochemical oxidation and reformed by subsequent chemical reduction. This reversible disruption and reformation of vesicles is attributed to the drastic change in the molecular structure of 11-FAB. To our knowledge, this is the first report of control over the formation and disruption of vesicles using two stimuli responses.

Unusual viscoelasticity behaviour in aqueous solutions containing a photoresponsive amphiphile.

Here, we report unusual behaviour of the viscoelasticity of surfactant aqueous solutions consisting of cationic cetyltrimethylammonium bromide (CTAB) and an anionic photoresponsive amphiphile, sodium [4-(4-butylphenylazo)phenoxy]acetate (C4AzoNa). When C4AzoNa molecules are trans-isomers, spheroidal micelles are formed in the surfactant solution, the viscosity of which is low. Irradiation of this solution by ultraviolet (UV) light yields an aqueous solution of CTAB/cis-C4AzoNa (cis-isomers of C4AzoNa), which is a highly viscous gel consisting of wormlike micelles. The drastic change in the surfactant solution viscosity is attributed to the formation and disruption of wormlike micelles. The geometrical structural transformation of the azobenzene groups in the C4AzoNa molecules of the CTAB/C4AzoNa mixture would lead to a change in the critical packing parameter of the mixture, thereby inducing the morphological transformation of the aggregates (spheroidal micelles to wormlike micelles). To our knowledge, this is the first report of a drastic increase in surfactant solution viscosity by UV light irradiation.

Addition of ascorbic acid to the extracellular environment activates lipoplexes of a ferrocenyl lipid and promotes cell transfection.

The level of cell transfection mediated by lipoplexes formed using the ferrocenyl lipid bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA) depends strongly on the oxidation state of the two ferrocenyl groups of the lipid (reduced BFDMA generally mediates high levels of transfection, but oxidized BFDMA mediates very low levels of transfection). Here, we report that it is possible to chemically transform inactive lipoplexes (formed using oxidized BFMDA) to "active" lipoplexes that mediate high levels of transfection by treatment with the small-molecule reducing agent ascorbic acid (vitamin C). Our results demonstrate that this transformation can be conducted in cell culture media and in the presence of cells by addition of ascorbic acid to lipoplex-containing media in which cells are growing. Treatment of lipoplexes of oxidized BFDMA with ascorbic acid resulted in lipoplexes composed of reduced BFDMA, as characterized by UV/vis spectrophotometry, and lead to activated lipoplexes that mediated high levels of transgene expression in the COS-7, HEK 293T/17, HeLa, and NIH 3T3 cell lines. Characterization of internalization of DNA by confocal microscopy and measurements of the zeta potentials of lipoplexes suggested that these large differences in cell transfection result from (i) differences in the extents to which these lipoplexes are internalized by cells and (ii) changes in the oxidation state of BFDMA that occur in the extracellular environment (i.e., prior to internalization of lipoplexes by cells). Characterization of lipoplexes by small-angle neutron scattering (SANS) and by cryogenic transmission electron microscopy (cryo-TEM) revealed changes in the nanostructures of lipoplexes upon the addition of ascorbic acid, from aggregates that were generally amorphous, to aggregates with a more extensive multilamellar nanostructure. The results of this study provide guidance for the design of redox-active lipids that could lead to methods that enable spatial and/or temporal control of cell transfection.