The determination of total phosphorus in seawater by nitrate oxidation of the organic component

A method is presented for the determination of total phosphorus dissolved in seawater by magnesium nitrate oxidation of the organic component concomitant with depolymerization of polyphosphate residues, followed by the standard molybdate colorimetric determination of the liberated orthophosphate. This method gave 93–100% recovery of phosphorus from inorganic metaphosphate and polyphosphate, phosphate esters and anhydrides, nucleotide-P, phospholipid and phosphonates. It is shown to be superior to the perchlorate-oxidation or high-intensity u.v.-irradiation methods for quantitative P recovery from phosphonates and polyphosphates, while proving equal in P recovery to the autoclave-requiring persulfate-oxidation method.     

Development of shape-engineered α-MnO2 materials as bi-functional catalysts for oxygen evolution reaction and oxygen reduction reaction in alkaline medium

In this work, three kinds of α-MnO₂ nano shapes, namely, nano-wires, nano-tubes and nano-particles have been prepared with a fine control over α-crystallographic form by employing hydrothermal procedure. The materials have been thoroughly characterized by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) spectrometry, field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The MnO₂ nano shapes are used as a model system for examining the shape-influenced bi-functional electrocatalytic activity towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in alkaline medium. The bi-functional role has been investigated by cyclic voltammetry and linear sweep voltammetry with rotating ring disc electrode (RRDE) techniques. It is found that α-MnO₂ nano-wires possess enhanced electrocatalytic activity compared to other two shapes namely nano-tubes and nano-particles despite the nano-tubes having a much higher specific surface area. The insight of bi-functional electrocatalytic activity is analysed in terms of catalyst surface with the help of first principles density functional theory (DFT) calculations based on the fact of surface energies and adsorption of water on the surface for a facile reaction.     

Preparation of pompon-like Co-B nanoalloy by a room-temperature solid-state-reaction as a catalyst for hydrolysis of borohydride solution

Pompon-like Co-B alloy composed of nanosheets with a large specific surface area of 202.4 m² g^?1 was synthesized via a facile room-temperature solid-state-reaction. By changing the mass ratios of CoCl₂·6H₂O to CO(NH₂)₂ in the synthesis, the morphology of the Co-B alloy can be controlled. Correspondingly, the specific surface area can increase from ca. 43.4–202.4 m² g^?1. When the pompon-like Co-B severs as a catalyst for the hydrolysis of NaBH₄, the hydrogen generation rate can be up to $8\text{.}26{\text{L}}_{\text{hydrogen}}{\text{min}}^{\mathrm{?}1}{{\text{g}}_{\text{catalyst}}}^{\mathrm{?}1}$. This value is larger compared with those of many other Co-B nanoalloys in previous reports. Additionally, the corresponding activated energy for the hydrolytic reaction is as low as 25 kJ mol^?1, hinting that the pompon-like Co-B catalyst possesses superior catalytic performance. The pompon-like Co-B alloy has the advantages of low cost, good recoverability, as well as high activity, which may find practical application in NaBH₄ hydrolysis for hydrogen production.     

Astragali Radix-derived nitrogen-doped porous carbon: An efficient electrocatalyst for the oxygen reduction reaction

The development of biomass-derived nitrogen-doped porous carbons (NPCs) for the oxygen reduction reaction (ORR) is important for sustainable energy systems. Herein, NPCs derived from Astragali Radix (AR) via a cost-effective strategy are reported for the first time. The as-prepared AR-950-5 catalyst shows a stacked layer-like structure and porosity. Notably, the optimized AR-950-5 delivers catalytic activity comparable to that of commercial Pt/C (C-Pt/C), with high onset potential, positive half-wave potential and large limiting current density. It also displays superior long-term stability and methanol tolerance for ORR. This work will pave the way for a new approach in the development of highly active and low-cost NPCs for fuel cells.     

Pt supported on boron,nitrogen co-doped carbon nanotubes (BNC NTs) for effective methanol electrooxidation

The research for electrocatalyst with high electroactivity and great CO-resistance ability for direct methanol fuel cells (DMFCs) is still a huge challenge. In this report, we develop Boron, Nitrogen co-doped carbon nanotubes (BNC NTs) as a support for Pt. Owing to the doping of boron, the catalyst not only provides extremely active sites for methanol oxidation reactions (MOR) but also protects Pt nanoparticles from agglutinating, performing superior electroactivity and excellent ability to anti CO poisoning. The X-ray photoelectron spectroscopy (XPS) results demonstrate the strong electron effect between Pt and B. Notably, the Pt/BNC NTs catalyst exhibits higher catalytic activity towards MOR and more superior durability in comparison with Pt/NC NTs and commercial JM Pt/C catalyst. The accelerated durability test (ADT) illustrates that Pt/BNC NTs catalyst can improve the issue of electrochemical surface area (ECSA) conservation, with only 30% diminish in comparison with the initial ECSA after 5000 cycles. The experiment result demonstrate that boron doping is the key step to improve the catalytic activities and CO-resistance ability due to the combination effects, involving firm B–C and N–C bonds, the stronger electron transfer in the nanotube structure among Pt, B and N, the stronger adsorption intensity of oxygen species from doped B.     

A cross-linked sheet structured poly(3,4-ethylenedioxythiophene) grown on Ni foam: Morphology control and application for long-life cyclic asymmetric supercapacitor

In this work, a cross-linked sheet structured conducting polymer ploy(3,4-ethylenedioxythiophene) (PEDOT) decorated on Ni foam is synthesized via one-step electrodeposition using the sodium p-toluenesulfonate (STSA) as surfactant and applied for supercapacitor electrode. The surfactants play a vital role in controlling the morphologies of PEDOT leading to the electrochemical performance difference. The optimized PEDOT electrode exhibits the highest capacitance of 711.6 mF cm⁻² at 3.0 mA cm⁻² in the three-electrode system. An asymmetric device (PEDOT/STSA//AC) is constructed by PEDOT/STSA (the positive electrode), activated carbon (AC) (the negative electrode) as well as 1 M Na₂SO₄ (the electrolyte). The device has been worked in a high-voltage range of 0–1.5 V, which displays the satisfied energy density of 14.0 Wh·kg⁻¹ at 535.5 W kg⁻¹. Furthermore, the PEDOT/STSA//AC device presents excellent rate capability and long-time cyclic stability.     

Phosphatized pseudo-core-shell Ni@Pt/C electrocatalysts for efficient hydrazine oxidation reaction

In this study, a series of phosphatized pseudo-core-shell Ni@Pt/C electrocatalysts has been obtained for efficient hydrazine oxidation reaction (HzOR). These (Ni@Pt–P/C) electrocatalysts were prepared by a primary replacement method followed by subsequent phosphating process. Among all Ni@Pt–P/C electrocatalysts, as-prepared Ni@Pt–P/C-400 electrocatalyst shows the highest HzOR performance (515 mA mg⁻¹_Pt), best stability, durability and lowest activation energy (12.60 kJ mol⁻¹). The satisfactory HzOR performance is mainly resulted from the unique design of phosphating effect on core-shell structure which producing good synergistic effect between Ni, P and Pt. This work would pave a way for developing other low-Pt catalysts in the future.     

MoS2-mesoporous LaFeO3 hybrid photocatalyst: Highly efficient visible-light driven photocatalyst

Perovskite type materials have high potential photocatalytic application towards both hydrogen energy generation and organic dye degradation due to their high stability and good reusability. Here, it is the first analysis of photocatalytic degradation of RhB and hydrogen energy evolution under visible light over MoS₂/LaFeO₃ nanocomposite. The physicochemical properties of the materials were characterized using a range of techniques such as XRD, TEM, XPS, FTIR, PL, photocurrent, etc. The optical properties of the nanocomposite show good absorption in UV-Vis spectra as compared to the bare LaFeO₃. In this study, MoS₂/LaFeO₃ nanocomposite was synthesized through single step in situ hydrothermal processes with a narrow bandgap, enhanced photocatalytic application under visible light. This novel MoS₂/LaFeO₃ nanocomposite is an efficient and promising photocatalyst for both hydrogen energy evolution and organic dye degradation.     

Facile fabrication of a binary NiCo phosphide with hierarchical architecture for efficient hydrogen evolution reactions

Exploring and designing efficient non-noble catalysts formed by element doping and nanostructure modification for the hydrogen evolution reaction (HER) is of critical importance with respect to sustainable resources. Herein, we have prepared a three-dimensional binary NiCo phosphide with hierarchical architecture (HA) composed of NiCoP nanosheets and nanowires grown on carbon cloth (CC) via a facile hydrothermal method followed by oxidation and phosphorization. Due to its unique hierarchical nanostructure, the NiCoP HA/CC electrocatalyst exhibits excellent performance and good working stability for the HER in both acidic and alkaline conditions. The obtained NiCoP HA/CC shows excellent HER activity with a low potential of 74 and 89 mV at 10 mA cm⁻², a small Tafel slope of 77.2 and 99.8 mV dec⁻¹ and long-term stability up to 24 h in acidic and alkaline electrolyte, respectively. NiCoP HA/CC, a non-noble metal material, is a promising electrocatalyst to replace noble metal-based electrocatalysts for the HER.