Electrochemical Co-reduction of N2 and CO2 to Urea Using Bi2S3 Nanorods Anchored to N-Doped Reduced Graphene Oxide.

Producing "green urea" using renewable energy, N2, and CO2 is a long-considered challenge. Herein, an electrocatalyst, Bi2S3/N-reduced graphene oxide (RGO), was synthesized by loading the Bi2S3 nanorods onto the N-RGO via a hydrothermal method. The Bi2S3/N-RGO composites exhibit the highest yield of urea (4.4 mmol g-1 h-1), which is 12.6 and 3.1 times higher than that of Bi2S3 (0.35 mmol g-1 h-1) and that of N-RGO (1.4 mmol g-1 h-1), respectively. N-RGO, because of its porous and open-layer structure, improves the mass transfer efficiency and stability, while the basic groups (-OH and -NH2) promote the adsorption and activation of CO2. Bi2S3 promotes the absorption and activation of inert N2. Finally, the defect sites and the synergistic effect on the Bi2S3/N-RGO composites work simultaneously to form urea from N2 and CO2. This study provides new insights into urea synthesis under ambient conditions and a strategy for the design and development of a new material for green urea synthesis.

Three-dimensional reduced graphene oxide decorated with cobalt metaphosphate as high cost-efficiency electrocatalysts for the hydrogen evolution reaction.

The development of cost-effective non-noble metal electrocatalysts is critical for the research of renewable energy. Transition metal cobalt metaphosphate-based materials have the potential to replace the noble metal Pt. Hence, in this work, we synthesize three-dimensional graphene-supported cobalt metaphosphate (Co(PO3)2-3D RGO) for the first time through the one-step hydrothermal synthesis method at low temperature with the aid of PH3 phosphating. In a 0.5 mol L-1 H2SO4 solution, the obtained electrocatalyst exhibits excellent electrochemical activity for the hydrogen evolution reaction (HER) with a small overpotential of 176 mV at a current density of 10 mA cm-2 and a Tafel slope of 63 mV dec-1. Additionally, in a 1 mol L-1 KOH solution, the electrocatalyst also shows outstanding HER activity with a small overpotential of 158 mV at a current density of 10 mA cm-2 and a Tafel slope of 88 mV dec-1. Co(PO3)2-3D RGO can maintain its catalytic activity for at least ten hours whether in acid or alkali. This work not only demonstrates an excellent electrocatalyst for the hydrogen evolution reaction, but also provides an extremely convenient preparation technology, which provides a new strategy for the development and utilization of high-performance electrocatalysts.

Boosting Hole Transfer in the Fluorine-Doped Hematite Photoanode by Depositing Ultrathin Amorphous FeOOH/CoOOH Cocatalysts.

The charge transfer is a key issue in the development of efficient photoelectrodes. Here, we report a method using F-doping and dual-layer ultrathin amorphous FeOOH/CoOOH cocatalysts coupling to enable the inactive α-Fe2O3 photoanode to become highly vibrant for the oxygen evolution reaction (OER). Fluorine doping is revealed to increase the charge density and improve the conductivity of α-Fe2O3 for rapid charge transfer. Furthermore, ultrathin FeOOH was deposited on F-Fe2O3 to extract photogenerated holes and passivate the surface states for accelerated charge carrier transfer. Moreover, CoOOH as an excellent cocatalyst was coated onto FeOOH/F-Fe2O3 with the photoassisted electrodeposition method remarkably expediting OER kinetics through an optional pathway of holes utilized by Co species. Ultimately, the CoOOH/FeOOH/F-Fe2O3 photoanode exhibits a satisfactory photocurrent density (3.3-fold higher than pristine α-Fe2O3) and a negatively shifted onset potential of 80 mV. This work showcases an appealing maneuver to activate the water oxidation performance of the α-Fe2O3 photoanode by an integration strategy of heteroatom doping and cocatalyst coupling.

A oxygen vacancy-modulated homojunction structural CuBi2O4 photocathodes for efficient solar water reduction.

The photoelectrochemical (PEC) water reduction performance of CuBi2O4 (CBO)-based photocathodes is still far from their theoretical values due to low bulk and surface charge separation efficiencies. Herein, we propose a regrowth strategy to prepare a photocathode with CBO coating on Zn-doped CBO (CBO/Zn-CBO). Furthermore, NaBH4 treatment of CBO/Zn-CBO introduced oxygen vacancies (Ov) on CBO/Zn-CBO. It was found that Zn-doping not only increases the charge carrier concentration of CBO, but also leads to appropriate band alignment to form homojunctions. This homojunction can effectively promote the separation of electron-hole pairs, thus obtaining excellent photocurrent density (0.5 mA cm-2 at 0.3 V vs. RHE) and charge separation efficiency (1.5 times than CBO). The following surface treatment induced Ov on CBO/Zn-CBO, which significantly increased the active area of the surface catalytic reaction and further enhanced the photocurrent density (0.6 mA cm-2). In the absence of cocatalysts, the electron injection efficiency of Ov/CBO/Zn-CBO was 1.47 times improved than that of CBO. This work demonstrates a homojunction photocathode with Ov modulation, which provides a new view for future photoelectrochemical water splitting.

Activating a hematite nanorod photoanode via fluorine-doping and surface fluorination for enhanced oxygen evolution reaction.

Poor charge separation and sluggish oxygen evolution reaction (OER) kinetics are two typical factors that hinder the photoelectrochemical (PEC) applications of hematite. Dual modification via heteroatom doping and surface treatment is an attractive strategy to overcome the above problems. Herein, for the first time, a hematite nanorod photoanode was ameliorated via the fluorine treatment (F-treatment) of both bulk and surface, enabling simultaneous charge separation from the interior to the interface. Accordingly, the novel photoanode (FeFx/F-Fe2O3) exhibited an outstanding PEC water oxidation activity, with a 3-fold improved photocurrent density than that obtained using unmodified α-Fe2O3. More specifically, fluorine doping (F-doping) in the hematite bulk remarkably increased the concentration of charge carriers and endowed it with favorable electrical conductivity for rapid charge transfer. Further surface F-treatment on F-doped α-Fe2O3 (F-Fe2O3) enriched the F-Fe bonds on the surface, which significantly boosted the OER kinetics and thereby inhibited the detrimental charge recombination. As a consequence, the efficiencies of bulk electron-hole pair separation and surface hole injection increased by 2.8 and 1.7 times, respectively. This study points to fluorine modulation as an attractive avenue to advance the PEC performance of metal oxide-based photoelectrode materials.

Layered Double Hydroxide onto Perovskite Oxide-Decorated ZnO Nanorods for Modulation of Carrier Transfer Behavior in Photoelectrochemical Water Oxidation.

Despite the fact that perovskite oxides with high photoelectrochemical (PEC) stability have gained widespread concern in the field of photo(electro)catalytic water splitting, the potential as a photoelectrode has not yet fully exploited. Herein, perovskite oxide-decorated ZnO nanorod photoanode improves the vital issue that photoproduced electron-hole pairs are apt to be quenched, in which type II band alignment between perovskite oxide and ZnO plays a crucial role in extracting carriers. Further, coupling with layered double hydroxide (LDH) onto the heterostructure not only tunes surface injection behavior of charge carriers by facilitating the interface reaction dynamics but also suppresses ZnO self-corrosion for extended durability. As a result, the optimized CoAl-LDH/LaFeO3/ZnO nanorod photoanode yields a much enhancive effect for the PEC property in terms of photocurrent density (2.46 mA cm-2 at 1.23 V vs reversible hydrogen electrode under AM 1.5G), onset potential, and stability. This work signifies a feasible design to combine promising perovskite oxides with the traditional photoelectrode system for achieving efficient water splitting.

Conformally Coupling CoAl-Layered Double Hydroxides on Fluorine-Doped Hematite: Surface and Bulk Co-Modification for Enhanced Photoelectrochemical Water Oxidation.

Earth-abundant hematite is an attractive photoanode for photoelectrochemical water splitting, whereas the intrinsic properties of inferior charge transfer and slow water oxidation kinetics still hinder its application. In response, an integrated photoanode has been constructed with hematite nanorod arrays modified by fluorine anion doping and further decorated with amorphous CoAl-layered double hydroxides (CoAl-LDH). This novel CoAl-LDH/F-Fe2O3 photoanode exhibited an excellent photocurrent density of 2.46 mA cm-2 at 1.23 V versus reversible hydrogen electrode (VRHE), five times enhanced than that of pristine α-Fe2O3. Systematic investigations reveal that fluorine anion serving as a donor dopant dramatically enhances the density of charge carrier and reduces the resistance of hematite for rapid charge transfer. Furthermore, the cocatalyst of CoAl-LDH could effectively passivate the surface defects of F-Fe2O3 and facilitate the water oxidation kinetics through an alternative pathway of holes trapped by Co species. As a consequence, the charge separation efficiencies of the bulk and surface were improved to 32.6 and 81.8%, respectively, compared with those of α-Fe2O3 (9.7 and 31.7%). Our results demonstrate that the dual modification of the bulk and surface is an attractive maneuver to ameliorate the water oxidation activity of hematite.

Hybrids of oxoisoaporphine-tetrahydroisoquinoline: novel multi-target inhibitors of inflammation and amyloid-ß aggregation in Alzheimer's disease.

A series of 8- and 11-substituted hybrids of oxoisoaporphine-tetrahydroisoquinoline have been designed and synthesized. The new derivatives strongly suppressed NO and iNOS production and modulated the production of cytokines by decreasing TNF-α and IL-1ß formation in lipopolysaccharide-activated BV-2 microglia and RAW 264.7 macrophages. Meanwhile, incubation of these derivatives with SH-SY5Y cells that were transfected with human APP containing the Swedish mutations significantly decreased the secretion of Aß42. Moreover, these hybrids could strongly inhibit the activity of acetylcholinesterase and butyrylcholinesterase. Further investigations in vivo indicated that the 8-substituted hybrid 3b significantly delayed paralysis caused by Aß1-42 toxicity in GMC101. In sum, these new hybrids could target multiple pathogenetic factors in Alzheimer's disease and merit further investigation.

Assessment of novel azaanthraquinone derivatives as potent multi-target inhibitors of inflammation and amyloid-ß aggregation in Alzheimer's disease.

A series of 6-substituted azaanthraquinone derivatives have been designed, synthesized, and their anti-inflammatory activities, antiaggregation effects on ß-amyloid proteins, anticholinesterase and neuroprotective activity were tested. The new derivatives strongly suppressed NO and iNOS production and modulate the production of cytokines by decreasing TNF-a, IL-1ß and IL-6 formation in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Meanwhile, the derivatives exhibited a significant in vitro inhibitory activity toward the self-induced Aß aggregation. While, treatment of SH-SY5Y cells overexpressing the Swedish mutant form of human b-amyloid precursor protein (APPsw) with derivatives was associated with significant reduction of Aß42 secretion levels. Moreover, the derivatives exhibited moderate inhibitory potency toward acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Further investigations indicated that compound 7b could attenuate H2O2-induced neurotoxicity toward SH-SY5Y neuroblastoma cells and half of the synthetic compounds were predicted to be able to cross the blood-brain barrier (BBB) to reach their targets in the central nervous system (CNS) according to a parallel artificial membrane permeation assay for BBB. Taken together, azaanthraquinone derivatives targeting multiple pathogenetic factors deserves further investigation for prevention and treatment of AD.

Dual Modification of a BiVO4 Photoanode for Enhanced Photoelectrochemical Performance.

Bismuth vanadate (BiVO4 ) has triggered extensive interest in photoelectrochemical (PEC) water splitting, owing to its narrow band gap and sufficiently positive valence band. However, some defects still exist to block the solar utilization efficiency and hydrogen evolution kinetics. Herein, the NiMoO4 semiconductor is combined with a BiVO4 photoanode, for the first time, and excellent PEC performance is achieved on the basis of heterojunction formation and favorable conductivity of NiMoO4 . In addition, it has been demonstrated that NiMoO4 promotes the light absorption ability, charge separation efficiency, and surface charge-transfer efficiency comprehensively. To further improve the photoconversion efficiency, cobalt phosphate, as an oxygen evolution reaction cocatalyst, is deposited on the above electrode and achieves a much enhanced utilization efficiency of 1.18 %, with a photocurrent density of 5.3 mA cm-2 at 1.23 V versus a reversible hydrogen electrode; this exceeds most results reported to date. This rational and unique photoanode construction provides a new thread for the photoelectrode designation.

Oxoisoaporphine alkaloid derivative 8-1 reduces Aß1-42 secretion and toxicity in human cell and Caenorhabditis elegans models of Alzheimer's disease.

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease and a growing health problem worldwide. Because the drugs currently used to treat AD have certain drawbacks such as single targeting, there is a need to develop novel multi-target compounds, among which oxoisoaporphine alkaloid derivatives are promising candidates. In this study, the possible anti-AD activities of 14 novel oxoisoaporphine alkaloid derivatives that we synthesized were screened and evaluated. We found that, in the 14 novel derivatives, compound 8-1 significantly reduced Aß1-42 secretion in SH-SY5Y cells overexpressing the Swedish mutant form of human ß-amyloid precursor protein (APPsw). Next, we found that compound 8-1 could down-regulate the expression level of ß-amyloid precursor protein (APP) in APPsw cells. Moreover, compound 8-1 significantly delayed paralysis in the Aß1-42-transgenic Caenorhabditis elegans strain GMC101, which could be explained by the fact that compound 8-1 down-regulated acetylcholinesterase activity, protected against H2O2-induced acute oxidative stress and paraquat-induced chronic oxidative stress, and enhanced autophagy activity. Taken together, our data suggest that compound 8-1 could attenuate the onset and development of AD.

Multitarget-directed oxoisoaporphine derivatives: Anti-acetylcholinesterase, anti-ß-amyloid aggregation and enhanced autophagy activity against Alzheimer's disease.

A series of 8- and 11-substituted oxoisoaporphine derivatives have been designed, synthesized, and tested for their ability to inhibit cholinesterase (ChE) in vitro and in vivo, and self-induced ß-amyloid (Aß) aggregation. Their autophagy activity and blood-brain barrier (BBB) permeability were also assessed. The new derivatives exhibited high AChE inhibitory activity in vivo and in intro. Over half the derivatives exhibited a significant in vitro inhibitory activity toward the self-induced Aß aggregation. While, treatment of SH-SY5Y cells overexpressing the Swedish mutant form of human ß-amyloid precursor protein (APPsw) with derivatives was associated with significant reduction of Aß secretion levels. Moreover, one-third of the synthetic compounds were predicted to be able to cross the BBB to reach their targets in the central nervous system (CNS) according to a parallel artificial membrane permeation assay for BBB. Compounds 5b and 6b were chosen for assessing their autophagy activity. The fluorescence intensity of the BC12921 was decreased significantly after treatment with compounds. The result encourages us to study such compounds thoroughly and systematically.