Hemoglobin-carbon nanotube derived noble-metal-free Fe 5 C 2-based catalyst for highly efficient oxygen reduction reaction

High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe 5 C 2 nanoparticles-studded sp 2 carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 ??C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO 4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm â '2 at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy productionope

Accelerated Bone Regeneration by Two-Photon Photoactivated Carbon Nitride Nanosheets

Human bone marrow-derived mesenchymal stem cells (hBMSCs) present promising opportunities for therapeutic medicine. Carbon derivatives showed only marginal enhancement in stem cell differentiation toward bone formation. Here we report that red-light absorbing carbon nitride (C3N4) sheets lead to remarkable proliferation and osteogenic differentiation by runt-related transcription factor 2 (Runx2) activation, a key transcription factor associated with osteoblast differentiation. Accordingly, highly effective hBMSCs-driven mice bone regeneration under red light is achieved (91% recovery after 4 weeks compared to 36% recovery in the standard control group in phosphate-buffered saline without red light). This fast bone regeneration is attributed to the deep penetration strength of red light into cellular membranes via tissue and the resulting efficient cell stimulation by enhanced photocurrent upon two-photon excitation of C3N4 sheets near cells. Given that the photoinduced charge transfer can increase cytosolic Ca2+ accumulation, this increase would promote nucleotide synthesis and cellular proliferation/differentiation. The cell stimulation enhances hBMSC differentiation toward bone formation, demonstrating the therapeutic potential of near-infrared two-photon absorption of C3N4 sheets in bone regeneration and fracture healing.ope

Mesoporous Silicon Hollow Nanocubes Derived from Metal-Organic Framework Template for Advanced Lithium-Ion Battery Anode

Controlling the morphology of nanostructured silicon is critical to improving the structural stability and electrochemical performance in lithium-ion batteries. The use of removable or sacrificial templates is an effective and easy route to synthesize hollow materials. Herein, we demonstrate the synthesis of mesoporous silicon hollow nanocubes (m-Si HCs) derived from a metal-organic framework (MOF) as an anode material with outstanding electrochemical properties. The m-Si HC architecture with the mesoporous external shell (???15 nm) and internal void (???60 nm) can effectively accommodate volume variations and relieve diffusion-induced stress/strain during repeated cycling. In addition, this cube architecture provides a high electrolyte contact area because of the exposed active site, which can promote the transportation of Li ions. The well-designed m-Si HC with carbon coating delivers a high reversible capacity of 1728 mAhg-1 with an initial Coulombic efficiency of 80.1% after the first cycle and an excellent rate capability of >1050 mAhg-1 even at a 15 C-rate. In particular, the m-Si HC anode effectively suppresses electrode swelling to ???47% after 100 cycles and exhibits outstanding cycle stability of 850 mAhg-1 after 800 cycles at a 1 C-rate. Moreover, a full cell (2.9 mAhcm-2) comprising a m-Si HC-graphite anode and LiCoO2 cathode exhibits remarkable cycle retention of 72% after 100 cycles at a 0.2 C-rate

Nickel-Based Electrocatalysts for Energy-Related Applications: Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions

The persistently increasing energy consumption and the low abundance of conventional fuels have raised serious concerns all over the world. Thus, the development of technology for clean-energy production has become the major research priority worldwide. The globalization of advanced energy conversion technologies like rechargeable metal-air batteries, regenerated fuel cells, and water-splitting devices has been majorly benefitted by the development of apposite catalytic materials that can proficiently carry out the pertinent electrochemical processes like oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and water hydrolysis. Despite a handful of superbly performing commercial catalysts, the high cost and low electrochemical stability of precursors have consistently discouraged their long-term viability. As a promising substitute of conventional platinum-, palladium-, iridium-, gold-, silver-, and ruthenium-based catalysts, various transition-metal (TM) ions (for example, Fe, Co, Mo, Ni, V, Cu, etc.) have been exploited to develop advanced electroactive materials to outperform the state-of-the-art catalytic properties. Among these TMs, nickel has emerged as one of the most hopeful constituents due to its exciting electronic properties and anticipated synergistic effect to dramatically alter surface properties of materials to favor electrocatalysis. This review article will broadly confer about recent reports on nickel-based nanoarchitectured materials and their applications toward ORR, OER, HER, and whole water splitting. On the basis of these applications and properties of nickel derivatives, a futuristic outlook of these materials has also been presented

Turn-on and Turn-off Fluorescent Probes for Carbon Monoxide Detection and Blood Carboxyhemoglobin Determination

Water-soluble, carbazole-based two-photon excitable fluorescent probes MPVC-I ("turn-on") and MPVC-II ("turn-off") are rationally designed and synthesized for the selective monitoring of carbon monoxide (CO). Both probes can effectively measure carboxyhemoglobin (HbCO) in the blood of the animals exposed to a CO dose as low as 100 ppm for 10 min. The palladium catalyzed azidocarbonylation reaction was optimized to improve the sensing efficiency

Ambient-Stable Cubic-Phase Hybrid Perovskite Reaching the Shockley-Queisser Fill Factor Limit via Inorganic Additive-Assisted Process

Additive-assisted organic-inorganic perovskite materials have attracted substantial attention as photovoltaic light absorbers which lead to outstanding power conversion efficiency. Here we report an easy and effective fabrication of cubic-phase perovskite with an inorganic molecule additive like hydrazinium chloride (N2H5Cl, to be denoted as HZCl). We predict that this inorganic cation of N2H5+, which can substitute for the organic A-site in the perovskite structure, can tune Fröhlich polaron properties by controlling the interaction strength and the number of proton coordinations to halide. This prediction is experimentally demonstrated with an optimized perovskite device with 2% N2H5Cl additive, which exhibits an unprecedented 85% fill factor (FF) with the highest value close to the Shockley-Queisser limit. An extra power conversion efficiency (PCE) of 2.3% and a fill factor (FF) efficiency of 14% are boosted. These optimized performances by additive effects lead to a new approach based on the theoretical calculation toward an improved performance of the perovskite solar cell

Band Gap Narrowing of Zinc Orthogermanate by Dimensional and Defect Modification

Dimensional reduction and defect control are powerful techniques for enhancing the physical and chemical properties of raw materials. Herein, we report the new type of sheetlike or two-dimensional-like zinc orthogermanate (Zn2GeO4, denoted as S-ZGO) with a one-step hydrothermal reaction and its application to photocatalytic water splitting. S-ZGO is directly grown along the surface of the Zn foil, since the growth rate of a crystal facet can be modified through the restricted reaction of dissolved precursor (GeO2) with a solid precursor (Zn foil) during the hydrothermal reaction. For further modification, the oxygen vacancies are introduced on the surface of S-ZGO using thermal hydrogen treatment and photodeposition-driven low amount of Pt/RuO2 co-catalysts loading. Notably, this reduced dimension decreases the band gap to 4.09 eV for S-ZGO (from 4.5 eV for the bulk), and the hydrogenation of S-ZGO further decreases the band gap to 3.88 eV. The origin of band gap narrowing is demonstrated with the density functional theory showing increased density of states at the edge of the conduction band (CB) and valence band (VB), and a new defect level between the CB minimum and VB maximum. As a possible application, we demonstrate that S-ZGO/H2 loaded with Pt/RuO2 exhibits the H2 rate of 167.0 ??mol h-1 g-1 and the O2 rate of 83.0 ??mol h-1 g-1, a8 times those of the rodlike ZGO photocatalysts

Intramolecular deformation of zeotype-borogermanate toward a three-dimensional porous germanium anode for high-rate lithium storage

We demonstrate a new class of synthetic process for three-dimensional porous Ge materials (3D-pGe). Starting from zeotype-borogermanate microcubes, the 3D-pGe sample was synthesized through a thermal deformation of artificial Ge-rich zeolite, etching, and subsequent hydrogen reduction. After the synthesis, the resultant byproducts were simply removed by warm water instead of a harmful etchant such as hydrofluoric acid. Benefiting from the structural advantages with meso/macro porosity in the overall framework, the as-prepared 3D-pGe exhibits good electrochemical properties as anode materials for lithium-ion batteries with a high capacity (770 mA h g(-1)), cycling stability (capacity retention over 83%) after 250 cycles at 1C, and excellent rate capability (32% for 10C with respect to C/5) as well as pseudocapacitive contribution by surface-controlled reaction. This study paves the way to a new synthesis strategy of 3D porous Ge anode materials from zeolite for large-scale energy storage application