Lausendencker9703

Chemical transformation of carbon dioxide (CO2) into fine chemicals such as oxazolidinones and carbamates is mainly reported using transition-metal complexes as homogeneous catalysts. selleck Herein, we demonstrate that a heterogeneous catalyst of highly dispersed Cu (Cu/NHPC) supported on hierarchically porous N-doped carbon (NHPC) can efficiently promote CO2 fixations to oxazolidinones and β-oxopropylcarbamates. The obtained NHPC, assembled by ultrathin nitrogen-doped carbon nanosheets with a three-dimensional (3D) structure, is readily prepared by pyrolysis of a nitrogen-containing polymer gel (NPG) in the presence of an activator of potassium bicarbonate (KHCO3). The resulting NHPC shows specific Brunauer-Emmet-Teller (BET) surface areas up to 2054 m2 g-1 with a mean micro/mesopore size of 0.55/3.2 nm and a broad macropore size distribution from 50 to 230 nm. The Cu/NHPC can efficiently promote three-component coupling of CO2, amines, and propargyl alcohols for syntheses of various oxazolidinones and β-oxopropylcarbamates with yields up to 99% and a wide substrate scope. Moreover, the Cu/NHPC exhibits excellent recyclability in CO2-to-oxazolidinone transformation during nine-time recycling. The research thus develops an NHPC-based heterogeneous Cu catalyst for green transformation of CO2.Cobalt carbonate hydroxide hydrate (CCHH) has long been functioning merely as a precursor to prepare compound catalysts; however, its intrinsic potential for the oxygen evolution reaction (OER) is quite limited due to its poor catalytic activity. Herein, a concept has been proposed to solve this issue by doping Fe into CCHH nanowires grown on nickel foam (denoted as Fe-CCHH/NF) for achieving efficient OER catalysis by electrochemical transformation. The obtained Fe-CCHH/NF-30 exhibits OER catalytic performance with an overpotential of only 200 mV versus the reversible hydrogen electrode (vs. RHE) at a current density of 10 mA cm-2 and small Tafel slope of 50 mV dec-1 in 1 M KOH. Moreover, it displays stability for over 130 h at a large current density of 55 mA cm-2, and no activity decline is observed after the 3000 cycle test. The performance of Fe-CCHH/NF-30 renders it one of the most promising OER catalysts. The density functional theory calculation reveals that the doped Fe can greatly enhance the OER activity by lowering the reactive energy barrier.Flexible and wearable energy storage microdevice systems with high performance and safety are promising candidates for the electronics of on-chip integration. Herein, we demonstrate inkjet-printed ultrathin electrodes based on molybdenum disulfide (MoS2) nanosheets for flexible and all-solid-state in-plane microsupercapacitors (MSCs) with high capacitance. The MoS2 nanosheets were uniformly dispersed in the low-boiling point and nontoxic solvent isopropanol to form highly concentrated inks suitable for inkjet printing. The MSCs were assembled by printing the highly concentrated MoS2 inks on a polyimide substrate with appropriate surface tension using a simple and low-cost desktop inkjet printer. Because of the two-dimensional structure of MoS2 nanosheets, the as-assembled planar MSCs have high loadings of active materials per unit area, resulting in more flexibility and thinness than the capacitors with a traditional sandwich structure. These planar MSCs can not only possess any collapsible shape through the computer design but also exhibit excellent electrochemical performance (with a maximum energy density of 0.215 mW h cm-3 and a high-power energy density of 0.079 W cm-3), outstanding mechanical flexibility (almost no degradation of capacitance at different bending radii), good cycle stability (85.6% capacitance retention even after 10,000 charge-discharge cycles), and easy scale-up. Moreover, a blue light-emitting diode can be powered using five MSCs connected in series. The in-plane and low-cost MSCs with high energy densities have great application potential for integrated energy storage systems including wearable planar solar cells and other electronics.Symmetry broken configurations within a long-range atomic arrangement exhibit new physical properties, and distinctive strategies are needed to resuscitate the localized symmetry by introducing measured defects, which can be attractive in displaying enhanced catalytic activities for energy applications. Our hypothesis is validated by introducing lattice defects due to the strain originating from a slightly higher doped grain boundary (GB) than at the interconnected grains of perovskite oxide. When Pd is doped at the B-site of ABO3-type La0.7Sr0.3CoO3-δ, a marginally higher ionic radius of Pd4+ than Co3+ enables partial deportation of Pd4+ to the GB. Consequently, the GB unit cell is relatively expanded with a higher interplanar spacing, as observed by microscopic analysis. When the Pd concentration is increased, oxygen vacancy sites are reduced and both metallic Pd and PdO x are exsolved at the perovskite oxide surface. With the Pd/Co ratio of 0.05, the defects originating from the Pd-modulated GB can be maximized to 1.29 ± 0.21% which enhances the bifunctional O2 activation ability by lowering the combined overpotential of oxygen evolution and reduction reactions (OER/ORR) to 0.91 V, duly corroborated by computational studies. The fabricated rechargeable Zn-air battery has a specific capacity of 740 mA·h/gZn (851 mW·h/gZn) when discharge is performed at 10 mA/cm2. Galvanostatic charge-discharge cycling with a 1 h cycle time shows 60 h stable performance. The OER/ORR bifunctional activity is found to be strongly correlated to the repositioned lattice symmetry at the perovskite GB.Metal-organic frameworks (MOFs) have been widely used as supporting materials to load or encapsulate metal nanoparticles for electrochemical sensing. Herein, the influences of morphology on the electrocatalytic activity of Co-containing zeolite imidazolate framework-67 (ZIF-67) as supporting materials were studied. Three types of morphologies of MOF ZIF-67 were facilely synthesized by changing the solvent because of the influence of the polar solvent on the nucleation and preferential crystal growth. Two-dimensional (2D) ZIF-67 with microplate morphology and 2D ultrathin ZIF-67 nanosheets were obtained from pure H2O (H-ZIF-67) and a mixed solution of dimethylformamide and H2O (D-ZIF-67), respectively. Three-dimensional ZIF-67 with rhombic dodecahedron morphology was obtained from pure methanol (M-ZIF-67). Then, one-step electrodeposition of silver nanostructures on ZIF-67-modified glassy carbon electrode (Ag/ZIF-67/GCE) was performed for the reduction of hydrogen peroxide (H2O2). Cyclic voltammetry can be used to investigate the electrocatalytic activity of Ag/ZIF-67/GCE, and Ag/H-ZIF-67/GCE displayed the best electrocatalytic property than Ag/D-ZIF-67/GCE and Ag/M-ZIF-67/GCE.