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

High-Affinity-Assisted Nanoscale Alloys as Remarkable Bifunctional Catalyst for Alcohol Oxidation and Oxygen Reduction Reactions

A key challenge in developing fuel cells is the fabrication of low-cost electrocatalysts with high activity and long durability for the two half-reactions, i.e., the methanol/ethanol oxidation reaction (MOR/EOR) and the oxygen reduction reaction (ORR). Herein, we report a conductivity-enhanced bifunctional electrocatalyst of nanoscale-coated Pt-Pd alloys on both tin-doped indium (TDI) and reduced graphene oxide (rGO), denoted as Pt-Pd@TDI/rGO. The mass activities of Pt in the Pt-Pd@TDI/rGO hybrid toward MOR, EOR, and ORR are 2590, 1500, and 2690 mA/mg, respectively. The ORR Pt specific activity and mass activity of the electrocatalyst are 17 and 28 times larger, respectively, than commercial Pt/C catalysts. All these remarkable catalytic performances are attributed to the role of TDI in enhancing the catalytic activity,by protecting Pt from oxidation as well as rapid mass/charge transfer due to the synergistic effect between surface Pt-Pd alloys and TDI/rGO

Engineered carbon-nanomaterial-based electrochemical sensors for biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.ope

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

Noncovalent Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications

This Review focuses on noncovalent functionalization of graphene and graphene oxide with various species involving biomolecules, polymers, drugs, metals and metal oxide-based nanoparticles, quantum dots, magnetic nanostructures, other carbon allotropes (fullerenes, nanodiamonds, and carbon nanotubes), and graphene analogues (MoS2, WS2). A brief description of pi-pi interactions, van der Waals forces, ionic interactions, and hydrogen bonding allowing noncovalent modification of graphene and graphene oxide is first given. The main part of this Review is devoted, to tailored functionalization for applications in drug delivery, energy materials, solar cells, water splitting, biosensing, bioimaging, environmental, catalytic, photocatalytic, and biomedical technologies. A significant part of this Review explores the possibilities of graphene/graphene oxide-based 3D superstructures and their use in lithium-ion batteries. This Review ends with a look at challenges and future prospects of noncovalently modified graphene and graphene oxideope

Zero-dimensional, one-dimensional, two-dimensional and three-dimensional nanostructured materials for advanced electrochemical energy devices

One of the biggest challenges of 21st century is to develop powerful electrochemical energy devices (EEDs). The EEDs such as fuel cells, supercapacitors, and Li-ion batteries are among the most promising candidates in terms of power-densities and energy-densities. The nanostructured materials (NSMs) have drawn intense attention to develop highly efficient EEDs because of their high surface area, novel size effects, significantly enhanced kinetics, and so on. In this review article, we briefly introduce general synthesis, fabrication and their classification as zero-dimensional (OD), one dimensional (1D), two-dimensional (2D) and three-dimensional (3D) NSMs. Subsequently, we focus an attention on recent progress in advanced NSMs as building blocks for EEDs (such as fuel cells, supercapacitors, and Li-ion batteries) based on investigations at the 0D, 1D, 2D and 3D NSMs. (C) 2011 Elsevier Ltd. All rights reserved.X11261237sciescopu

Recent progress in the development of anode and cathode catalysts for direct methanol fuel cells

Continuous growth in global energy demand has sparked concerns about energy security and environmental sustainability. In the past two decades, attempts have been made in the development of innovative energy technologies. The direct methanol fuel cell (DMFC) is among the most promising alternative energy sources for the near future. Simple construction, compact design, high energy density and relatively high energy-conversion efficiency give the DMFC an advantage over other promising power sources in terms of portability. However, the translation of DMFCs into commercially successful products is precluded due to poor performance. In addition, low activity, poor durability and reliability and an expensive anode and cathode further discourage the application of DMFCs. In this regard, the present review article focuses on recent progress in the development of anode and cathode catalysts for DMFCs. The first part of the review discusses the recent developments in the synthesis of single-, double-, and multiple-component catalysts and new catalyst supports for anode electrodes. The section is followed by the chemical approaches employed to make alloys and composite catalysts, aiming to enhance their activity, reliability and durability for the methanol oxidation reaction. Finally, exciting new research that pushes the development of single-, double-, and multiple-component catalysts and new catalyst supports for cathode electrodes is introduced. In addition, size-, shape- and composition-dependent electrocatalysts that are advocated for methanol oxidation at the anode and oxygen reduction at the cathode are highlighted to illustrate the potential of the newly developed electrocatalysts for DMFC applications. Moreover, this article provides a comprehensive review of the experimental work that is devoted to understanding the fundamental problems and recent progress in the development of anode and cathode catalysts for DMFCs.close251

Covalent versus Charge Transfer Modification of Graphene/Carbon-Nanotubes with Vitamin B1: Co/N/S-C Catalyst toward Excellent Oxygen Reduction

High-performance nonprecious cathodic catalysts for oxygen reduction are highly demanded for low-temperature polymer electrolyte membrane fuel cells (PEMFCs). Here, we report a noble-meta- free, nitrogen and sulfur codoped graphene(G)/carbon-nanotube(CNT) material decorated with Co nanoparticles (NPs), which serve as catalytic sites for excellent oxygen reduction reaction (ORR) in basic and acidic media. Out of the cathodic catalysts synthesized by either covalent (cov) or charge transfer (CT) modification of graphen oxide (GO) with thiamine (Th: Vitamin B1), ThG/CNT/Co-cov shows more promising ORR properties than ThG/CNT/Co-CT. Catalyst ThG/CNT/Co-cov exhibits onset/halfwave potentials of 0.95/0.86 V in 0.1 M KOH and 0.92/0.83 V in 0.1 M HClO4, which are comparable to those of commercial catalyst Pt/C (0.95/0.86 V). As compared to Pt/C, our catalyst shows higher current densities of 6.72 mA cm-2 in basic medium and 7.08 mA cm-2 in acidic medium at 0.55 V (vs reversible hydrogen electrode (RHE)). It also exhibits better catalytic stability and methanol tolerance. High catalytic efficiency and stability of ThG/CNT/Co-cov show a promising prospect of materialization of PEMFCs for clean energy production.clos

Thermal Transformation of Carbon Hybrid Materials to Graphene Films

We demonstrate a simple approach to grow graphene films on polycrystalline nickel (Ni) foils, in which polycrystalline carbon hybrid materials (CHMs) were used in sandwich structures (molybdenum-CHMs-Ni-molybdenum) as a carbon source for graphene, and pressure was then applied to the sandwich. The CHMs were transformed into single as well as few layer graphene by a segregation–precipitation process. The applied pressure not only increased the density of the graphene films but also reduced the vaporization of dissociated carbon molecules of the CHMs. We have explored the possibility to grow graphene films in low vacuum (5 × 10^–1 Pa) at relatively low temperatures (≤750 °C). The formation of the graphene films at 750 °C is simple and cost-effective and can be scaled up

Interconnected Pt-nanodendrite/DNA/reduced-graphene-oxide hybrid showing remarkable oxygen reduction activity and stability

Controlling the morphology and size of platinum nanodendrites (PtDs) is a key factor in improving their catalytic activity and stability. Here, we report the synthesis of PtDs on genomic-double-stranded-DNA/reduced-grapheneoxide (gdsDNA/rGO) by the NaBH4 reduction of H2PtCl6 in the presence of plant gdsDNA. Compared to industrially adopted catalysts (i.e., state-of-the-art Pt/C catalyst, Pt/rGO, Pt3Co, etc.), the as-synthesized PtDs/gdsDNA/rGO hybrid displays very high oxygen reduction reaction (ORR) catalytic activities (much higher than the 2015 U.S. Department of Energy (DOE) target values), which are the rate-determining steps in electrochemical energy devices, in terms of onset-potential, halfwave potential, specific-activity, mass-activity, stability, and durability. Moreover, the hybrid exhibits a highly stable mass activity for the ORR over a wide pH range of 113. These exceptional properties would make the hybrid applicable in nextgeneration electrochemical energy devices.close2