In this work, we report a new, economical, scalable synthetic strategy to prepare pure carbon spheres (CSs) without dopants or residual metal. The CSs gave rise to an excellent oxygen reduction reaction (ORR) performance in terms of activity and reaction kinetics. They showed particularly superior stability: there was no attenuation of the half-wave potential for CSs-20 h-900 after 13 500 cycles of CV in O2-saturated 0.1 M KOH. Our results confirmed the significant role of intrinsic defects for high-activity ORR without the need to include other dopants. The study of carbon defects shed fresh light on the true origin of the activity of metal-free ORR catalysts and is fundamentally important and technically promising for promoting the development of other original, low-cost, high-efficiency carbon-based metal-free electrocatalysts.

Electrochemical and corrosion behavior of AZ31B magnesium alloy have been investigated using electrochemical methods in a composite solution of MgSO4–Mg(NO3)2 (0.14 mol L−1 MgSO4, 1.86 mol L−1 Mg(NO3)2) under different sodium fluoride (NaF) concentrations. The surface of the AZ31B magnesium alloy is characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The experimental results indicate that the magnesium electrode achieves a low corrosion rate and high reactivity in the selected composite solution. Furthermore, the effect of NaF on the AZ31B magnesium alloy in the composite electrolyte is investigated in detail and the results demonstrated that the inhibition efficiency increased up to 80% and the delay time was reduced by four times when the NaF concentration reaches 30 mmol L−1. Thus, NaF could efficiently reduce corrosion rate and improve the discharge activity of the magnesium anode as it changes the composition of the surface film. We believe that the composite electrolyte of MgSO4–Mg(NO3)2 with optimized concentration of NaF is a promising candidate for improving the corrosion resistance and reducing the delayed action of AZ31B alloy in aqueous solution.

An in-situ synthetic route is designed to prepare manganese dioxide (MnO2) nanosphere supported on graphdiyne oxides (GDYO) that is applied as electrode material for supercapacitors. The electrochemical measurements reveal that the MnO2@GDYO composite has a specific capacitance of 301 and 170 F g−1 at the current density of 0.2 and 10 A g−1, which is prior to the supercapacitor performance of MnO2@GDY. The cyclic stability test presents that MnO2@GDYO has a 98% initial capacitance retention even after 3000 charge-discharge cycles. The attractive supercapacitor performance of the composite material MnO2@GDYO make it potentially a promising candidate for future energy storage systems.Download high-res image (146KB)Download full-size image

Magnesium (Mg) is a promising anode material for primary Mg batteries because of its outstanding characteristics, such as abundance, light weight, and low cost. However, self-corrosion and delayed action of Mg alloy in aqueous solution limit its performance and reduce the energy density. In this work, the influence of NaF–Na3PO4 on electrochemical behaviors of Mg alloy in composite solution is studied by electrochemical impedance spectroscopy, galvanostatic discharge, and linear sweep voltammetry. The morphology and microstructure are analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. Impedance studies show that NaF and Na3PO4 are good inhibitors with the inhibition efficiency reaches 98.8%. Moreover, the delayed time is reduced to 0.08 s, despite that soaking time length is extended to 16 days. A Mg–MnO2 cell demonstrates an excellent discharge capacity of 1539 mAh g−1 at the discharge current density of 5 mA cm−2.

•Porous carbon network was prepared by fish-scale pyrolysis and activated by ZnCl2.•This carbon network exhibits good ORR catalytic activity and stability in alkaline condition.•The formation of three-dimentional network can facilitate the enhancement of ORR activity.•Pyridinic- and graphitic-N may be mainly responsible for the electrocatalytic activity.Recycling and utilizing organic biowastes will effectively help to decrease the damage to the natural environment and synchronously facilitate the development of new carbon materials for energy applications. In this study, we directly convert protein-rich fish-scale biowaste to hierarchically porous three-dimentional (3D)-network nanocarbons via two-step pyrolysis process combined with ZnCl2 activation and acidic-treatment. It is interestingly found that this material exhibits more excellent oxygen reduction electrocatalytic activity and stability compared to the commercial 20 wt% Pt/C catalyst in both alkaline and acidic solutions, which can be closely correlated to its chemical state of nitrogen atoms, BET surface area and inner porous structure. The addition of ZnCl2 activator during pyrolysis process can help to produce the 3D network nanostructure and then to enhance the mesopore surface area, making for the improvement of oxygen reduction performance. More remarkably, the ORR onset potential on our material is about 60 mV higher than that on the Pt/C catalyst in alkaline electrolyte. In addition, we also propose that pyridinic- and graphitic-nitrogen species may be key factors to be responsible for the electrocatalytic activity. This study can encourage the exploration of high porosity nanocarbons from widely-existed biowastes, functioning as highly active and stable oxygen reduction electrocatalysts.Download high-res image (170KB)Download full-size image

Low-cost facile fabrication of highly efficient non-precious-metal catalysts to replace commercial Pt-based catalysts for oxygen reduction reaction (ORR) has attracted great attentions, because it is significant for rapid commercialization of fuel cells. Based on a fact that graphdiyne, another member of the carbon family, has not been systematically investigated as a new carbon support to ORR catalysts. We here report an effective strategy for easy synthesis of a cheap iron-nitrogen-doped carbon nanolayers wrapped around graphdiyne core-shell electrocatalyst (Fe-PANI@GD-900) for ORR from one-step pyrolysis of iron and polyaniline loaded onto graphdiyne nanocomposite at 900 °C. Electrochemical results indicate that the catalyst exhibits unexpectedly high ORR activity with onset and half-wave potentials of 1.05 V and 0.82 V (vs. RHE), while its mass activity at given potentials is lower than that of the Pt/C catalyst. Moreover, Fe-PANI@GD-900 follows a direct four-electron reduction pathway, and its long-term stability is superior to Pt/C and other graphdiyne-based catalysts previously reported in the literature. The relatively excellent ORR performance may be largely attributed to the formation of high contents of graphitic-N and FeN compounds, and the addition of graphdiyne facilitating to absolutely accelerate ORR charge transfer and fully expose more N-doped active sites on the surface.Download high-res image (394KB)Download full-size image

•The actual amount of dehydration was consistent with the theoretical amount.•The intermediate products of amorphous chromium hydroxide were more complex.•At the temperature of 289 °C, the CrOOH was formed in both samples.•Nanocrystalline chromium hydroxide included three dehydration processes.•The amorphous chromium hydroxide included four dehydration processes.Chromic oxide was synthesized through the dehydration and thermal decomposition of nanocrystalline and amorphous chromium hydroxide. The dehydration of amorphous chromium hydroxide had been researched clearly over the past few decades. Here, we mainly explored the different dehydration process between crystalline and amorphous chromium. The two samples were prepared by a simple one-step precipitation at 5 °C and 25 °C, and characterized using X-ray diffraction and high resolution transmission electron microscopy. The evolution of dehydration and thermal decomposition behaviors of the two samples were measured by derivative thermogravimetry and Fourier transform infrared (FT-IR) spectrometry. The dehydration of nanocrystalline chromium hydroxide occurred at 105 °C, 289 °C, and 409 °C, whereas that of amorphous chromium hydroxide occurred at 70 °C, 289 °C, 406 °C, and 443 °C. At approximately 289 °C, the actual quality of dehydration was only one water molecule, which was in agreement with the theoretical result (expressed as CrOOH). The FT-IR absorption bands at 3370 and 1620 cm−1 gradually decreased in intensity with increasing annealing temperature and then finally disappeared at 600 °C to become α-Cr2O3.

•A graphene-based catalyst doped by Co and N atoms was prepared by simple pyrolysis.•Doping of Co and acid-treatment facilitate the conversion of inert-N to active-N.•Pyridinic- and pyrrolic-nitrogen groups may play a key role in the ORR process.The development of low cost, active and stable non-precious metal (Co-N/C) catalysts to replace commercial Pt-based catalysts for oxygen reduction reaction (ORR) is a hot topic to this day. In this work, we have synthesized a new graphene-based catalyst (Co-N/C-A) doped by cobalt and nitrogen atoms with high contents of pyridinic- and pyrrolic-nitrogen (planar nitrogen), which exhibits ORR electrocatalytic activity with onset and peak potentials of 0.035 and −0.082 V (versus Hg/HgO) in 0.1 mol l−1 KOH solution, respectively. Besides, it has much higher stability and tolerance to methanol compared to the commercial Pt/C catalyst. The overall electron transfer number is calculated to be about 3.8. The transition-metal (Co) in the precursor can promote the formation of active sites during pyrolysis process and the followed acid-treatment may effectively expose the active sites on the surface of the catalyst, helping to enhance the ORR activity. It can be also proposed that pyridinic- and pyrrolic-nitrogen groups may play a key role in the ORR process and serve as the ORR active centers.

Metal-catalyzed transfer hydroformylation is an important way of cleaving C–C bonds and constructing new double bonds. The newly reported density functional theory (DFT) method, M11-L, has been used to clarify the mechanism of the rhodium-catalyzed transfer hydroformylation reported by Dong et al. DFT calculations depict a deformylation and formylation reaction pathway. The deformylation step involves an oxidative addition to the formyl C–H bond, deprotonation with a counterion, decarbonylation, and β-hydride elimination. After olefin exchange, the formylation step takes place via olefin insertion into the Rh–H bond, carbonyl insertion, and a final protonation with the conjugate acid of the counterion. Theoretical calculations indicate that the alkalinity of the counterion is important for this reaction because both deprotonation and protonation occur during the catalytic cycle. A theoretical study into the formyl acceptor shows that the driving force of the reaction is correlated with the stability of the unsaturated bond in the acceptor. Our computational results suggest that alkynes or ring-strained olefins could be used as formyl acceptors in this reaction.

The development of nitrogen-rich biomass-derived carbon catalysts provides an attractive perspective to substitute for Pt-based electrocatalysts for oxygen reduction reaction (ORR). We here report a facile strategy for synthesis of a nitrogen-doped biocarbon/graphene-like composite electrocatalyst by pyrolyzing a solid-state mixture of coprinus comatus biomass and melamine under nitrogen protection. The graphtic carbon nitride formed by polycondensation of melamine at 600 °C acts as a self-sacrificing template to generate the nitrogen-doped graphene-like sheet, which can function as an inserting agent and self-generating support. The composite catalyst exhibits the most promising catalytic activity towards the four-electron ORR with a half-wave potential of around 0.83 V (vs. RHE), and more excellent stability and tolerance to methanol/ethanol compared to the commercial Pt/C catalyst. It is interestingly found that both a higher content of nitrogen and a larger ratio of graphitic-nitrogen species, which may derive from self-addition of graphene-like support into the catalyst, can effectively improve the electrocatalytic activity. The planar N group may be the nitrogen functionality that is most responsible for maintaining the ORR activity in alkaline medium. This study can largely encourage the exploration of high-performance carbon-based catalysts from economical and sustainable fungus biomass.

Nitrogen-doped carbon materials are known to exhibit good electrocatalytic activity for the oxygen reduction reaction (ORR). However, the structure of the active site for the ORR remains unknown. In this work, a series of nitrogen-doped carbon nanospheres (N-CNSs) were successfully prepared by using porcine blood protein as specific nitrogen source at different pyrolysis temperatures. The results show that the catalyst with a higher percentage of the planar N species (83.5% in total nitrogen content), possesses outstanding ORR electrocatalytic activity close to the commercial 40% Pt/C catalyst in alkaline media, and significantly superior stability and immunity for methanol crossover than that of 40% Pt/C. Metal Fe particles in the precursor can facilitate the partial transformation of oxidized N to planar N and the joint incorporation of planar pyridinic and pyrrolic N groups into the carbon matrix during high-temperature pyrolysis, which further produces more defective and exposed edges in the carbon structure. It is here proposed that both planar pyridinic and pyrrolic nitrogen atoms may be the N functionalities that are most responsible for the ORR electrocatalytic activity and can function as ORR active sites for as-prepared catalysts.

•An ORR electrocatalyst was fabricated from blood biomass and carbon nanotube.•The N-CNT catalyst exhibits good ORR activity, methanol resistance and stability.•The pyrolysis process produces high contents of pyridinic and pyrrolic N species.•The pyridinic-N group may play more important role in the active sites for ORR.Here we present a facile synthetic route to design nitrogen-doped nanostructured carbon-based electrocatalyst for oxygen reduction reaction (ORR) by the copyrolysis of blood biomass from pig and carbon nanotubes (CNTs) at high temperatures. The nitrogen-doped CNTs obtained at 800 °C not only results in excellent ORR activity with four-electron transfer selectivity in alkaline medium, but also exhibits superior methanol-tolerant property and long-term stability. It is confirmed that high-temperature pyrolysis processes can facilitate to produce higher contents of pyridinic- and pyrrolic-N binding groups in electrocatalysts, contributing to the enhancement of ORR performance in terms of onset potential, half-wave potential, and limited current density. We also propose that the planar-N configuration may be the active site that is responsible for the improved ORR electrocatalytic performance. The straight-forward and cheap synthesis of the active and stable electrocatalyst makes it a promising candidate for electrochemical power sources such as fuel cells or metal-air batteries.

A novel ether/BF3 reductive system has been described, in which diphenylmethanols and their ether and ester derivatives are used as starting materials. Reductions are performed in ether under reflux and an argon atmosphere, and the addition of extra water is beneficial to this reduction. A series of alkanes are able to be prepared with good to excellent yields. A deuterated experiment exhibits that the reductive hydrogen is generated from ether. The mechanism is discussed in detail to explain the observed reactivity.

The influence of cerium and lanthanum conversion coatings on AZ63 magnesium alloy surface was investigated by Tafel polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The results show that the dual rare-earth conversion film treated in the mixture solution containing cerium nitrate and lanthanum nitrate is denser and more uniform than that in single rare-earth solution. EDX and XPS analysis demonstrates that the coatings are composed of rare earth oxides and hydrated hydroxides. The cerium and lanthanum conversion coatings can improve the corrosion resistance of AZ63 magnesium alloy evidently. The inhibition effect of dual rare-earth film on magnesium alloy increases with the increase of immersion time. With the extension of aging time, the inhibition effect increases first and then decreases. The coating aged for 48 h possesses the best inhibition effect.

•A novel N-containing electrocatalyst for ORR was fabricated by using pyrolysis of blood protein.•Addition of carbon support into carbonization process may produce better catalytic activity.•High-temperature pyrolysis process can transfer the pyridinic-N to pyrrolic-N significantly.•The content of pyrrolic-N group plays an important role in improvement of the ORR catalytic activity.We report a new strategy to design carbon-based electrocatalysts containing nitrogen through the co-pyrolysis of blood protein and carbon black support. The results show that the nitrogen in electrocatalysts is primarily in the form of pyridinic- and pyrrolic-type nitrogen species. High-temperature pyrolysis processes can transfer a significant amount of pyridinic-N to pyrrolic-N. The electrocatalyst containing a higher amount of the pyrrolic-N configuration exhibits better electrocatalytic activity towards oxygen reduction reaction in terms of onset potential, half-wave potential, and limited current density. It is suggested that the pyrrolic-N configuration may be the electrocatalytically active site and may be responsible for the enhanced ORR performance in alkaline media. The carbon black support also plays an important role in the pyrolysis process, improving the ORR catalytic activity.

Research on magnesium battery has three primary fields as follows: changing the metallurgical factors of the magnesium electrode material to improve discharge performance, identifying inhibitors to form a protective film to reduce self-corrosion of magnesium alloys, and improving the electrochemical properties of the electrolyte to improve discharge continuity. During the research and development of the magnesium battery, the voltage delay that occurs in the discharge process is a critical issue because it limits the application of Mg/MnO2 cells. This paper provides an overview of the relationship between the voltage delay of magnesium primary battery and magnesium anode corrosion. Furthermore, the factors affecting the voltage delay were analyzed, and the existing problems in the study of the voltage delay of magnesium battery were identified.

A non-precious metal catalyst CoMe/C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The catalytic activity of CoMe/C is characterized by the electrochemical linear sweep voltammetry technique. The onset reduction potential of the catalyst is 0.55 V (vs. SCE) at a scanning rate of 5 mV/s in 0.5 mol/L H2SO4 solution. The formation of the ORR activity sites of CoMe/C is facilitated by metallic β-cobalt.The activities to oxygen reduction reaction of AB in 0.5 mol/L H2SO4 solution saturated by O2 (a), CoMe/C600 catalyst in 0.5 mol/L H2SO4 solution saturated by N2 (b) and saturated by O2 (c), and Pt-disk electrode (Ф 2 mm) in 0.5 mol/L H2SO4 solution saturated by O2 (d).

There is a growing interest in designing more effective fuel cell cathode catalyst precursors. Here the partial pyrolysis of animal bloods has been used to produce the blood pyropolymers, which are an intermediate substance between a polymer and carbonaceous material. These pyropolymers were yielded by carbonization process below 600°C. The structural changes in the pyropolymers were characterized by X-ray diffraction, and their formation was checked by micro-IR spectra, thermogravimetric and differential thermal analysis. Their potential electrocatalytic properties were evaluated using the linear sweep voltammetry in the O2-saturated KOH solution. It is found that the process of pyropolymer formation began about 200°C and completed around 500°C. The change of particle phase depends on the formation of the pyropolymers, but has no effect to their internal carbon structures which are controlled by pyrolysis process only. Meanwhile, it is confirmed that the crystalline phases in the pyropolymers can exist at the surface of heat-treated materials. It can be also found that the carbon materials are active toward oxygen reduction and their activity is associated with the carbonization level. Our study will stimulate the designers to design the highly active catalysts by using native blood pyropolymers as the precursors.

Under open-flask conditions in the presence of commercially available FeCl3·6H2O, N,N-disubstituted anilines can be converted into diversely functionalized benzidines with yields of up to 99%. Oxidative coupling was extended to N-monosubstituted anilines, and the method was applied to the efficient preparation of 6,6′-biquinoline. Mechanistic investigations have also been performed to explain the observed reactivities.

This work takes advantage of electrochemically anodic pretreated carbon paste electrode modified with acetylene black nanocarbon particles (AB/CPE), a new and high-sensitive analytical method for insulin was put forward. Modern voltammetric testing techniques were used for primarily investigating the redox electrochemical characterization of Fe(CN)63−/4− and electrochemical behavior of insulin on nanocarbon electrode surface. At the same time, a plausible mechanism was also proposed to provide insights into understanding how to facilitate the electron transfer between insulin biomolecule and electrode surface. The results have shown that the pretreated AB/CPE represented high accumulation efficiency to insulin and promoted its direct electron transfer rate owing to the presence of nanocarbon particles and anodic pretreatment. It is found that insulin exhibited a very sensitive anodic peak at 0.47 V on the pretreated AB/CPE, and its peak current was increased about six times more than that on the pretreated carbon paste electrode (CPE). A linear relationship between the anodic peak current and the concentration of insulin from 20 to 1000 nM and a limit of detection as low as 5 nM were obtained using the pretreated AB/CPE. Attracting attention, the proposed method was applied to the realistic samples successfully and showed good recovery and reproducibility.

A non-precious metal Co-N/C catalyst for the oxygen reduction reaction (ORR) was synthesized by heating a mechanical mixture of cobalt chloride, urea and acetylene black under a nitrogen atmosphere. The catalyst was characterized by XRD and XPS. The electrocatalytic activity in the ORR was evaluated by linear sweep voltammetry in 0.5 mol L−1 H2SO4 solution. The results show that the Co-N/C catalyst aids the reduction of oxygen. The presence of elemental cobalt in the precursor allows nitrogen atoms to embed themselves in the graphite matrix to form pyridinic and graphitic type C-N structures as the ORR active sites. The effect of heat-treating temperature on the catalytic activity was also investigated. The results also show that the Co-N/C catalyst is most active when pyrolyzed at 600°C. The obtained Co-N/C catalyst loses some activity after initial exposure to the H2SO4 solution because of leaching, but is then stable for up to 20 h immersion. The catalyst is also stable when charged, which is supported by the cyclic voltammetry results.

Metallic cobalt was deposited on acetylene black to synthesize a composite Co/C by chemical reduction method. A platinum-free electrocatalyst Co–N/C(8 0 0) for oxygen reduction reaction (ORR) was synthesized by mixing the composite Co/C with urea and heat-treating at 800 °C. The results from linear sweep voltammograms indicated that the Co–N/C(8 0 0) is active to ORR. The β-Co and cobalt oxides are not the active site of the catalyst Co–N/C. However, the existence of cobalt facilitated the modification of nitrogen to carbon black and led to the formation of active site of catalyst Co–N/C(8 0 0).

The impedance of a capacitively coupled contactless conductivity detector (C4D) cell was experimentally examined for different cell parameters by alternative current impedance (ACImp). The effect of the gap between the electrodes and the length of the electrodes on the impedance behavior of the C4D cell has been studied. As a result, the impedance of C4D cell is largely defined by the length of the gap between the electrodes and the length of the electrodes. The impedance increases with increasing gap between the electrodes and the length of the electrodes. It could be found that tightly coupling of the electrodes to the outer wall of the capillary is needed. The axial contactless conductometric detector can be effectively described by the simplest possible equivalent circuitry consisting of a capacitor, resistor, a second resister and a Warburg impedance. These results are helpful to understand the impedance characteristics of C4D cell and improve its detective performance.

The development of nitrogen-rich biomass-derived carbon catalysts provides an attractive perspective to substitute for Pt-based electrocatalysts for oxygen reduction reaction (ORR). We here report a facile strategy for synthesis of a nitrogen-doped biocarbon/graphene-like composite electrocatalyst by pyrolyzing a solid-state mixture of coprinus comatus biomass and melamine under nitrogen protection. The graphtic carbon nitride formed by polycondensation of melamine at 600 °C acts as a self-sacrificing template to generate the nitrogen-doped graphene-like sheet, which can function as an inserting agent and self-generating support. The composite catalyst exhibits the most promising catalytic activity towards the four-electron ORR with a half-wave potential of around 0.83 V (vs. RHE), and more excellent stability and tolerance to methanol/ethanol compared to the commercial Pt/C catalyst. It is interestingly found that both a higher content of nitrogen and a larger ratio of graphitic-nitrogen species, which may derive from self-addition of graphene-like support into the catalyst, can effectively improve the electrocatalytic activity. The planar N group may be the nitrogen functionality that is most responsible for maintaining the ORR activity in alkaline medium. This study can largely encourage the exploration of high-performance carbon-based catalysts from economical and sustainable fungus biomass.

This work takes advantage of electrochemically anodic pretreated carbon paste electrode modified with acetylene black nanocarbon particles (AB/CPE), a new and high-sensitive analytical method for insulin was put forward. Modern voltammetric testing techniques were used for primarily investigating the redox electrochemical characterization of Fe(CN)63−/4− and electrochemical behavior of insulin on nanocarbon electrode surface. At the same time, a plausible mechanism was also proposed to provide insights into understanding how to facilitate the electron transfer between insulin biomolecule and electrode surface. The results have shown that the pretreated AB/CPE represented high accumulation efficiency to insulin and promoted its direct electron transfer rate owing to the presence of nanocarbon particles and anodic pretreatment. It is found that insulin exhibited a very sensitive anodic peak at 0.47 V on the pretreated AB/CPE, and its peak current was increased about six times more than that on the pretreated carbon paste electrode (CPE). A linear relationship between the anodic peak current and the concentration of insulin from 20 to 1000 nM and a limit of detection as low as 5 nM were obtained using the pretreated AB/CPE. Attracting attention, the proposed method was applied to the realistic samples successfully and showed good recovery and reproducibility.