Crystalline/amorphous composite interface of CoP@Ni/Fe-P as a boosted electrocatalyst for full water splitting.

Heterojunction materials have become good candidates for electrocatalysts thanks to their unique physicochemical merits. Herein, a crystalline-amorphous CoP@Ni/Fe-P heterojunction is constructed for whole water splitting. Originating from the strong electronic reaction at the amorphous-crystal interfaces, the electron density of Co, Ni, Fe and P is adjusted, which will optimize the adsorption and desorption energy of intermediates for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) and lower the kinetic barrier. The CoP@Ni/Fe-P heterojunction displays overpotentials of 125 and 250 mV to drive a current density of 10 mA cm-2 in 1 M KOH. In addition, the whole water splitting performance requires a cell voltage of 1.56 V to deliver 10 mA cm-2 and shows good stability. This work provides a way to design and prepare transition-metal-based materials with good electrocatalytic activity by constructing a crystalline and amorphous heterojunction.

Emerging Heterogeneous Supports for Efficient Electrocatalysis.

Electrocatalysis plays a fundamental role in many fields, such as metallurgy, medicine, chemical industry, and energy conversion. Anchoring active electrocatalysts with controllable loading and uniform dispersion onto suitable supports has become an attractive topic. This is because the supports can not only have the potential to improve catalytic activity and stability through the interaction between support and catalytic center, but also can reduce precious metal consumption by improving atomic utilization. Herein, recent theoretical and experimental progresses concerning the development of supports to anchor electrocatalytic materials are first reviewed. Next, their controllable syntheses, characterization techniques, metal-support electronic interactions, and structure-performance relationships are presented. Some representative carbon supports and non-carbonaceous supports, as well as recently reported star supports such as 2D supports, single atom catalysts, and self-supported catalysts are also summarized. In addition, the significant role of support in stabilizing and regulating catalytic active sites is particularly emphasized. Finally, challenges, opportunities, key problems, and further promising solutions for supported catalysts are proposed.

Optimizing the SEM specimen preparation method for accurate microanalysis of carbon nanotube/nanocluster hybrids.

Scanning electron microscopy (SEM) integrated with energy-dispersive X-ray spectrometry (EDS) are scientifically used to characterise the morphology, chemical composition and elemental distribution of powder samples. Upon an accessible analytical instrument, the specimen preparation method directly affects the quality and accuracy of the observation and analysis. In this paper, three preparation methods were utilised to characterise the carbon nanotubes (CNTs) based materials, and their strengths as well as the limitations are discussed. Thus, a characterisation strategy was established by comparing the obtained three measurement together with the derived sample information. To the end, we proposed to acquire the backscattered electron (BSE) images of nanoscale heavier nanoclusters grafted CNTs, typically for wide functional applications such as energy conversion and storage. Our proposed optimum method works particularly on the clarification of powder samples with small particle sizes and low atomic numbers, which underscores the involved contribution of SEM backscattered electron images.

Nonprecious Bimetallic Sites Coordinated on N-Doped Carbons with Efficient and Durable Catalytic Activity for Oxygen Reduction.

Developing efficient, inexpensive, and durable electrocatalysts for the oxygen reduction reaction (ORR) is important for the large-scale commercialization of fuel cells and metal-air batteries. Herein, a hierarchically porous bimetallic Fe/Co single-atom-coordinated N-doped carbon (Fe/Co-Nx -C) electrocatalyst for ORR is synthesized from Fe/Co-coordinated polyporphyrin using silica template-assisted and silica-protection synthetic strategies. In the synthesis, first silica nanoparticles-embedded, silica-protected Fe/Co-polyporphyrin is prepared. It is then pyrolyzed and treated with acidic solution. The resulting Fe/Co-Nx -C material has a large specific surface area, large electrochemically active surface area, good conductivity, and catalytically active Fe/Co-Nx sites. The material exhibits a very good electrocatalytic activity for the ORR in alkaline media, with a half-wave potential of 0.86 V versus reversible hydrogen electrode, which is better than that of Pt/C (20 wt%). Furthermore, it shows an outstanding operational stability and durability during the reaction. A zinc-air battery (ZAB) assembled using Fe/Co-Nx -C as an air-cathode electrocatalyst gives a high peak power density (152.0 mW cm-2 ) and shows a good recovery property. Furthermore, the performance of the battery is better than a corresponding ZAB containing Pt/C as an electrocatalyst. The work also demonstrates a synthetic route to a highly active, stable, and scalable single-atom electrocatalyst for ORR in ZABs.

Tunable engineering hollow carbon nanomaterial served as an excellent catalyst for oxygen reduction reaction and hydrogen evolution reaction.

Fe and N functionalized hollow carbon spheres (Fe/N-HCS) with hierarchically porous structure are constructed. Remarkably, it is discovered that the pyrolysis temperature effects the chemical composition intensively. At 800 °C, only graphitic-N and oxidized-N are formed for all as-prepared samples. The surface area and pores can be precisely tuned, the surface area of all Fe/N-HCS samples is more than 500  m2 g-1 benefiting from the porous hollow structure. Thus, the optimized Fe/N-HCS exhibits excellent oxygen reduction reaction performance in term of onset potential (1.00 V vs. RHE), half-wave potential (0.87 V vs. RHE), good stability as well as methanol tolerance for oxygen reduction reaction, even surpassing the Pt in alkaline condition and more competitive in acidic condition; Furthermore, the optimized Fe/N-HCS displays better hydrogen evolution reaction activity in acidic condition with onset overpotential of 40 mV and overpotential to deliver 10 mA cm-2 at 170 mV, indicating better active. It is found that Fe/N-HCS improve the hydrogen evolution reaction activity after electrodeposition trace quantity of Pt, which shows 170 mV of overpotential to deliver 100 mA cm-2. X-ray photoelectron spectroscopy result indicates the loading of Pt is roughly 0.11 at%, thus, the improved performance is basically due to the synergistic effect between Pt and Fe/N-HCS.

A Facile Synthesis of Nitrogen-Doped Highly Porous Carbon Nanoplatelets: Efficient Catalysts for Oxygen Electroreduction.

The oxygen reduction reaction (ORR) is of great importance for various renewable energy conversion technologies such as fuel cells and metal-air batteries. Heteroatom-doped carbon nanomaterials have proven to be robust metal-free electrocatalysts for ORR in the above-mentioned energy devices. Herein, we demonstrate the synthesis of novel highly porous N-doped carbon nanoplatelets (N-HPCNPs) derived from oatmeal (or a biological material) and we show the materials' high-efficiency as electrocatalyst for ORR. The obtained N-HPCNPs hybrid materials exhibit superior electrocatalytic activities towards ORR, besides excellent stability and good methanol tolerance in both basic and acidic electrolytes. The unique nanoarchitectures with rich micropores and mesopores, as well as the high surface area-to-volume ratios, present in the materials significantly increase the density of accessible catalytically active sites in them and facilitate the transport of electrons and electrolyte within the materials. Consequently, the N-HPCNPs catalysts hold a great potential to serve as low-cost and highly efficient cathode materials in direct methanol fuel cells (DMFCs).

Three-dimensional N,B-doped graphene aerogel as a synergistically enhanced metal-free catalyst for the oxygen reduction reaction.

Here, a novel N,B-doped graphene aerogel, abbreviated as N,B-GA, was obtained via a two-step approach and served as a metal-free catalyst for the oxygen reduction reaction (ORR). This two-step method involved a hydrothermal reaction and a pyrolysis procedure, guaranteeing the efficient insertion of the heteroatoms. The resulting three-dimensional (3D) N,B-GA obtained at pyrolysis temperature of 1000 °C exhibited outstanding catalytic activity for the oxygen reduction reaction (ORR), comparable to that of Pt/C. In addition, the catalytic activity of this 3D N,B-GA was obviously better than that of the nitrogen-doped graphene aerogel (N-GA) and boron-doped graphene aerogel (B-GA) in terms of the onset potential, half-wave potential and diffusion limiting current density. The superior catalytic reactivity arises from the synergistic coupling of the B and N dopants within the graphene domains.

Advanced oxygen reduction reaction catalyst based on nitrogen and sulfur co-doped graphene in alkaline medium.

A novel nitrogen and sulfur co-doped graphene (N-S-G) catalyst for oxygen reduction reaction (ORR) has been prepared by pyrolysing graphite oxide and poly[3-amino-5-mercapto-1,2,4-triazole] composite (PAMTa). The atomic percentage of nitrogen and sulfur for the prepared N-S-G can be adjusted by controlling the pyrolysis temperature. Furthermore, the catalyst pyrolysed at 1000 °C, denoted N-S-G 1000, exhibits the highest catalytic activity for ORR, which displays the highest content of graphitic-N and thiophene-S among all the pyrolysed samples. The electrocatalytic performance of N-S-G 1000 is significantly better than that of PAMTa and reduced graphite oxide composite. Remarkably, the N-S-G 1000 catalyst is comparable with Pt/C in terms of the onset and half-wave potentials, and displays larger kinetic limiting current density and better methanol tolerance and stability than Pt/C for ORR in an alkaline medium.

2-(2-Fluoro-4-nitro-phen-oxy)-3-nitro-pyridine.

In the title compound, C11H6FN3O5, the dihedral angle between the aromatic rings is 72.4 (3)°. The NO2 groups form dihedral angles of 40.8 (2) and 4.8 (2)°, respectively, with the attached pyridine and benzene rings. The crystal structure features π-π stacking between centrosymmetrically related pairs of pyridine rings [centroid-centroid separation = 3.800 (3) Å].

A novel cobalt tetranitrophthalocyanine/graphene composite assembled by an in situ solvothermal synthesis method as a highly efficient electrocatalyst for the oxygen reduction reaction in alkaline medium.

A novel micro/nano-composite, based on cobalt(II) tetranitrophthalocyanine (CoTNPc) grown on poly(sodium-p-styrenesulfonate) modified graphene (PGr), as a non-noble-metal catalyst for the oxygen reduction reaction (ORR), is fabricated by an in situ solvothermal synthesis method. The CoTNPc/PGr is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The electrocatalytic activity of the CoTNPc/PGr composite toward the ORR is evaluated using cyclic voltammetry and linear sweep voltammetry methods. The CoTNPc/PGr composite exhibits an unexpected, surprisingly high ORR activity compared to CoTNPc or PGr. The onset potential for ORR on CoTNPc/PGr is found to be around -0.10 V vs. SCE in 0.1 M NaOH solution, which is 30 mV and 70 mV more positive than that on PGr and CoTNPc, respectively. The peak current density on CoTNPc/PGr is about 2 times than that on PGr and CoTNPc, respectively. Rotating disk electrode (RDE) measurements reveal that the ORR mechanism is nearly via a four-electron pathway on CoTNPc/PGr. The current density for ORR on CoTNPc/PGr still remains 69.9% of its initial value after chronoamperometric measurements for 24 h. Pt/C catalyst, on the other hand, only retains 13.3% of its initial current. The peak potential shifts slightly and current barely changes when 3 M methanol is added. The fabricated composite catalyst for ORR displays high activity, good stability and excellent tolerance to the crossover effect, which may be used as a promising Pt-free catalyst in alkaline direct methanol fuel cells (DMFCs).

A dopamine sensor based on a methoxypolyethylene glycol polymer covalently modified glassy carbon electrode.

A dopamine (DA) sensor based on a methoxypolyethylene glycol (MPEG) polymer covalently modified glass carbon electrode (GCE) was fabricated by an electroadsorption method. The electrochemical behavior of the sensor towards the catalytic oxidation of DA in pH 5.0 phosphate buffer solution (PBS) was investigated by cyclic voltammetry. The modified electrode obviously enhanced the current response and decreased the overpotentials for the oxidation of DA. Using differential pulse voltammetry, the sensor gave a linear response to DA over the concentration range of 2.0-140 µM with a detection limit (S/N = 3) of 4.68 × 10(-8) M. It was found that MPEG can complex DA through hydrogen bonding interaction between ethylene oxide units of the polymer and the protonated dopamine in acidic PBS and preconcentrate it in the film, which improved the detection limit and sensitivity of DA. The DA sensor exhibits good sensitivity, selectivity and stability, and has been applied for the determination of DA in dopamine hydrochloride injection solution.

Alloyed (ZnSe)(x)(CuInSe2)(1-x) and CuInSe(x)S(2-x) nanocrystals with a monophase zinc blende structure over the entire composition range.

Metastable zinc blende CuInSe(2) nanocrystals were synthesized by a hot-injection approach. It was found that the lattice mismatches between zinc blende CuInSe(2) and ZnSe as well as CuInSe(2) and CuInS(2) are only 2.0% and 4.6%, respectively. Thus, alloyed (ZnSe)(x)(CuInSe(2))(1-x) and CuInSe(x)S(2-x) nanocrystals with a zinc blende structure have been successfully synthesized over the entire composition range, and the band gaps of alloys can be tuned in the range from 2.82 to 0.96 eV and 1.43 to 0.98 eV, respectively. These alloyed (ZnSe)(x)(CuInSe(2))(1-x) and CuInSe(x)S(2-x) nanocrystals with a broad tunable band gap have a high potential for photovoltaic and photocatalytic applications.