•3D-NG@SiO2-2-900 is prepared by pyrolyzing POPD, with silica colloid as templates.•The number of graphene layers and the pore diameter of 3D-NG@SiO2 are controllable.•3D-NG@SiO2-2-900 has super ORR catalytic performance and durability in 0.1 M KOH.•High porosity, many planar nitrogen and mass transmission channel benefit the ORR.Three-dimensional nitrogen-doped graphene (3D-NG@SiO2) is prepared by pyrolyzing poly (o-phenylenediamine) (POPD) with high nitrogen content. POPD is prepared via an in situ chemical oxidation polymerization of o-phenylenediamine (OPD) in acetic acid with silica colloid as templates. The optimum parameter is OPD:SiO2 = 1:2, pyrolysis @ 900 °C. SEM and TEM images show the wrinkled and porous graphene structures. Raman spectra indicate that 3D-NG@SiO2 consists of 4–6 layers graphene. N2 adsorption–desorption isotherms reveal that the pore size distributions mainly centralize at 5–10 nm. XRD illustrates the amorphous structure. XPS analysis shows that the nitrogen content is 3.6% and nitrogen mainly exists in the form of pyridinic nitrogen and pyrrolic nitrogen. The oxygen reduction reaction (ORR) performance investigated using a rotating disk electrode shows that the initial potential of 3D-NG@SiO2 is 0.08 V (vs. Hg/HgO). The electron transfer number is 3.92 @ −0.3 V (vs. Hg/HgO), indicating that 3D-NG@SiO2 mainly occurs via a four-electron process. The oxygen reduction current density decreases by 21% after 60 h in the chronoamperometry test. The CVs manifests a current density loss of 0.16 mA cm−2 after scanning for 5000 cycles. The high activity and durability indicate the promising potential of 3D-NG@SiO2 as ORR catalysts.Download high-res image (353KB)Download full-size image

•Compatible SPEEK/PBI high temperature PEMs were prepared by SPEEK-Na and PBI.•The intense ionic crosslinking bonds were formed between SPEEK and PBI.•The performances of SPEEK/PBI membranes improved enormously.•Conductivities at different temperatures and RH were tested with good results.Highly sulfonated poly (ether ether ketone) (SPEEK)/polybenzimidazole (PBI) composite high temperature proton exchange membranes were prepared. To enhance the compatibility of SPEEK and PBI, SPEEK was transformed into SPEEK-Na and the prepared SPEEK-Na/PBI was immersed in dilute acid to obtain desired ionic crosslinking SPEEK/PBI membrane. Scanning electron microscope results showed that PBI formed a dense structure. Energy dispersive X-ray spectroscopy of the cross-section of composite membranes and X-ray diffraction declared that PBI were uniformly distributed in SPEEK without phase separation. Fourier-transform infrared spectroscopy indicated the intense ionic bonds between SO3H and N-basic group. Because of the intense interaction, SPEEK/PBI composite membranes could not only significantly improve the mechanical strength and oxidation resistance, but also reduce the swelling degree and methanol crossover. Thermogravimetric analysis results revealed that the membranes could be used below 200 °C. The proton conductivity of the SPEEK/PBI (20 wt%) composite membranes could reach 0.1985 S cm−1 at 170 °C and 100% relative humidity (RH). Proton transfer activation energy was 49.31 kJ mol−1. At 50% RH, the conductivity was 0.099 S cm−1 at 180 °C and it remained the value of 0.0084 S cm−1 at 180 °C in dry oven. The methanol permeability of SPEEK/PBI (20 wt%) membrane was 3.96 × 10−8 cm2 s−1 at 70 °C. The composite membrane appeared to be potential for usage in direct methanol fuel cells.

Lanthanum sulfophenyl phosphate (LaSPP) was synthesized by m-sulfophenyl phosphonic acid and lanthanum nitrate. UV-Vis spectrophotometry and Fourier-transform infrared spectroscopy indicate that the desired product was obtained and its elementary composition and typical layered structure were determined by energy dispersive X-ray spectroscopy and scanning electron microscopy. Transmission electron microscopy (TEM) proved its typical layered structure and X-ray diffraction spectroscopy indicated its good crystallinity and the interlayer distance of about 15.67 Å, which matches the value obtained by TEM (2.0 nm). Thermogravimetry and differential thermal analysis revealed good thermal stability of LaSPP. Proton conductivity of LaSPP was measured at different temperatures and relative humidities (RH), reaching values of 0.123 S cm−1 at 150°C and 100 % RH. Proton transfer activation energy was 22.52 kJ mol−1. At 160°C and 50 % RH, the conductivity was 0.096 S cm−1. In the drying oven, the conductivity retained the value of 1.118 × 10−2 S cm−1. The results show that LaSPP is a highly effective inorganic-organic conductor.

•MnO2 nanorod adsorbed with supports (non-support, carbon black, and MWCNT) is prepared.•Structures between nanorod and MWCNT are parallel, cross and bend intersect.•The MnO2/MWCNTs possess good ORR performance and durability.•The magnesium–air cell of MnO2/MWCNTs has excellent discharge performance and stability.MnO2 nanorods adsorbed with different supports (non-support, carbon black, and MWCNTs) were prepared through hydrothermal method for magnesium–air fuel cells (MAFCs). The morphological characteristics of the catalysts indicate that the combination modes of nanorods and MWCNTs are parallel, cross, and bend intersect, which provide a large surface areas and enhance electron transfer process. X-ray diffraction pattern illustrates the crystal form of MnO2, and X-ray photoelectron spectroscopy reveals that the existing form of manganese is Mn4+. The ORR performance investigated using a rotating disk electrode shows that the initial reduction potential of MnO2/C and MnO2/MWCNTs in the LSV curves are −0.02 and 0.03 V vs. Hg/HgO (+0.098 V vs. NHE), respectively. The electron transfer number of MnO2/MWCNTs is 3.86, which corresponds to four electrons. In the I–t curves, the oxygen reduction current density of MnO2/MWCNTs decreases by 18.1% and MnO2/C decays by 27.9% after 60 h. The CVs reveal that the current density losses of MnO2/MWCNTs and MnO2/C are 0.4 and 0.8 mA cm−2 after scanning for 5000 cycles. The potential values of the air electrode loaded with MnO2/C and MnO2/MWCNTs catalysts are −0.78 and −0.62 V vs. SCE, respectively, at 150 mA cm−2, respectively. The discharge performance of a single-chamber MAFC shows that the peak power densities of MnO2/C and MnO2/MWCNTs are 60.95 and 70.47 mW cm−2, respectively, 20 °C in 10 wt% NaCl solutions. The single cells of MnO2/MWCNTs can continuously discharge for more than 24 h at a current density of 20 mA cm−2. The EIS proves that the conductivity of MnO2/MWCNTs is higher than MnO2/C.

IronIII sulfophenyl phosphate (FeSPP) is successfully synthesized by an optimized process from the reaction of ironIII chloride and m-sulfophenyl phosphonic acid (msPPA) by a simple and environmentally friendly method. Experimental results show FeSPP has a kind of layered structure, and multilayer sheet is about 2 nm thick. FeSPP exhibits good thermal stability and does not decompose under 200 °C. Protons transfer through vehicle and Grotthuss mechanisms at different relative humidities (RH). The conductivity of FeSPP can reach to 0.115 S/cm at 180 °C and RH = 100 %. Under this condition, vehicle mechanism plays the leading role, and the Grotthuss mechanism plays the minor role. At low RH, Grotthuss plays the leading role, and vehicle plays the minor role. In a drying oven at 180 °C, the proton conductivity remains 2.15 × 10−3 S/cm. Good conductivities at different RH and thermal stabilities clearly demonstrate that FeSPP is a highly effective conductor. It can be used as catalysts, chemical sensors, and in the preparation of composite membrane.

•A planar iron-polyphthalocyanine (PPcFe) with a large-area π bond is synthesized.•PPcFe/C exhibits high oxygen reduction activity.•Spectral and electrochemical studies show that PPcFe/C has excellent durability.•A magnesium/PPcFe/C-air cell has excellent discharge performance and stability.A planar iron-polyphthalocyanine (PPcFe) oxygen reduction reaction (ORR) catalyst for magnesium air fuel cells (MAFC) is prepared by dispersing PPcFe on carbon black (C) and heating under argon. Thermogravimetric analysis shows PPcFe is stable below 600 °C. The X-ray diffraction and X-ray photoelectron spectroscopy results show the active site of PPcFe/C is the FeN4 in the phthalocyanine ring. The rotating disk electrode measurements in 0.5 M L−1 H2SO4 solution show the initial potential for ORR is 0.82 V vs. RHE at 20 °C and that it mainly occurs via a four-electron process. Almost no performance degradation is observed over continuous cyclic voltammetry at 10,000 cycles, linear sweep voltammetry at 200 cycles, and 60 h of the chronoamperometry test. The infrared spectrum of PPcFe, after all the durability tests, shows no changes from the initial characteristics. The polarization curves of the air electrodes with PPcFe/C, iron-phthalocyanine/C and Pt/C catalysts exhibit excellent polarization performances. The discharge performance of a MAFC single cell with PPcFe/C cathode catalyst shows an open circuit potential of 1.74 V, with a peak power density of 50.5 mW cm−2 at 20 °C. The cell voltage decreases less than 0.01 V during continuing discharge @ 20 mA cm−2 for more than 11 h.

Porous polytetrafluoroethylene (PTFE) membranes were used as support material for sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK)/zirconium sulfophenyl phosphate (ZrSPP)/PTFE composite membranes. The membranes were prepared via a spray painting method. Membranes were characterized by thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The composite membranes exhibited good thermal stabilities. SEM micrographs confirmed that the pores of the PTFE were filled entirely with SPPESK and ZrSPP. The resulting composite membranes were mechanically durable, dimensionally stable in alternating wet/dry environments, and had lower methanol permeabilities compared with the unsupported SPPESK/ZrSPP composite membranes reported in our previous work. The water uptake of these membranes was also lower than previous SPPESK/ZrSPP composite membranes. The proton conductivity of PTFE supported SPPESK (DS 81%)/ZrSPP(10 wt%) composite membrane was as high as 0.24 S/cm at 120 °C. Thus, the composite membranes exhibited good thermal stabilities, proton conductivities, and good methanol resistance, indicating that these composite membranes could serve as effective alternative membranes for direct methanol fuel cells (DMFCs).

Cerium sulfophenyl phosphate (CeSPP), a novel inorgano–organic solid proton conductor, was synthesized from the reaction of m-sulfophenyl phosphonic acid and hydrated cerous nitrate. The synthesized CeSPP was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The TGA results reveal that CeSPP has good thermal stability. The synthesized CeSPP exhibited considerable high-proton conductivity. The proton conductivity was about 0.13 S/cm at 150 °C under 100% relative humidity. The proton conductivity at 105 °C at different RH was also measured.Cerium sulfonphenyl phosphate (CeSPP), as a novel inorgano–organic solid proton conductor, was synthesized from the reaction of m-sulfophenyl hosphonic acid (msPPA) and hydrated cerous nitrate. It has a similar layered structure to ZrSPP. The CeSPP exhibited good thermal stability and considerably high-proton conductivity. The proton conductivity is about 0.13 S/cm at 150 °C under 100% relative humidity (RH).Research Highlights► Cerium sulfophenyl phosphate (CeSPP) was first synthesized. ► It is a novel inorgan-organic solid proton conductor. ► The CeSPP has good thermal stability. ► CeSPP also exhibited considerably high-proton conductivity at high temperature.

Novel polymer composite membranes composed of sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) and inorgano-organic zirconium sulfophenyl phosphate (ZrSPP) were prepared by solution casting. Three ZrSPP concentrations were used: 10, 20 and 30 wt%. The degrees of sulfonation (DS) of SPPESK were 34.6% and 76%. The DS of ZrSPP was 95%. Membranes were characterized by infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). IR results indicated intense hydrogen bonds formed between ZrSPP and SPPESK molecules. SEM micrographs showed that ZrSPP mixed well with SPPESK and formed dense structures. The proton conductivity of the 10 wt% SPPESK (DS 76%)/ZrSPP composite membrane reached 0.393 S/cm at 120 °C and that of the 30 wt% of SPPESK (DS 34.6%)/ZrSPP composite membrane reached 0.23 S/cm at 160 °C and 100% relative humidity (RH). Proton conductivities of the SPPESK/ZrSPP composite membranes were better than that of the Nafion®117 membrane in the temperature range of 80–160 °C. The methanol permeabilities of the SPPESK/ZrSPP composite membranes were in the range of 1.9 × 10−8 to 0.15 × 10−8 cm2/s, much lower than that of Nafion®117 (2.4 × 10−6 cm2/s). The composite membranes exhibited good thermal stabilities, proton conductivities, and good methanol resistance properties.

In this work, a novel catalyst is prepared by dispersing planar polyphthalocyanine cobalt (PPcCo) synthesized by polymerizing cobalt (II)-4, 4′,4″,4‴-phthalocyanine tetracarboxylic acid (TcPcCo) using a high surface area carbon powder (Vulcan XC 72), and then heat-treated in argon (Ar) atmosphere. The polymer and PPcCo/C catalysts are characterized systematically by a variety of methods, such as ultraviolet–visible (UV–vis) spectrophotometer, Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscope (TEM). Results show that the PPcCo obtained is stable below 600 °C. The active site of PPcCo/C is CoN4 in phthalocyanine ring, and the PPcCo is dispersed homogeneously on the surface of XC 72. Electrocatalytic properties and electrochemical stability of the catalysts in 0.5 mol L−1 H2SO4 are evaluated by RDE measurements. The initial potential for O2 reduction in O2-saturated H2SO4 is 0.81 V and it catalyzed O2 reduction mainly through a four-electron process. Almost no performance degradation is observed over continuous cyclic voltammetry (CV) at 10,000 cycles (4 days). Polarization curves obtained by linear sweep voltammetry (LSV) at 200 cycles also show no change. PPcCo/C catalysts display significant electrocatalytic performance for O2 reduction, tolerance towards methanol, and long-term stability.

Ultraviolet–visible and fourier transform infrared absorption spectra indicate that polytetraphenylporphyrin Co (II) (PTPPCo) can be obtained by heat-treating 5,10,15,20-tetra (4-carboxyphenyl)-porphyrin Co (II) (TCPPCo) at 400 °C in argon atmosphere. Polytetraphenylporphyrin Co/C is obtained by heat treatment (HT) of TCPPCo, which is adsorbed on Vulcan XC-72 with different Co–N4 loading, from 400 °C to 1000 °C in argon atmosphere. Catalysts are evaluated for electroreduction performances of oxygen on modified electrodes in sulfuric acid solutions. Results from electroreduction of the catalyst (HT 600 °C and 6 wt% Co–N4 loading) show the original reduction voltage is 0.81 V versus the reversible hydrogen electrode, and the transfer electron number is 3.83. The morphology, distribution, and surface elemental analysis of the catalysts are characterized by x-ray diffraction spectroscopy and transmission electron microscopy with energy dispersive x-ray. PTPPCo can homogeneously anchor on the carbon support and withstand decomposition upon heat treatment at 600 °C. Since TCPPCo results in polymerization on XC-72, pi (π) bond increases significantly with the decrease in π-electron delocalization energy. Improved capacity in electron gain or loss is observed, and the center of electrocatalysis is clearly exposed. Thus, the activity, stability, and selectivity of the catalyst presented in this paper are proven better than those of other common catalysts.

•Zirconium phytate (ZrP) was prepared as a novel inorganic-organic proton conductor.•Tuning Zr/P molar ratio enhanced the proton conductivity and avoids acid leaching.•ZrPA(3:4) exhibited an ion exchange capacity of 1.04 meq/g at room temperature.•High proton conductivity at high temperature and different humidity were achieved.Zirconium phytate (ZrPA) was prepared via gelation of zirconyl chloride and phytic acid in certain ratios. Fourier-transform infrared spectroscopy was applied to confirm the structure and interactions between Zr4+ and phytate ions, including hydrogen bonding and chelation. Scanning and transmission electron microscopic study have shown that ZrPA has a fusiform shape and a layered structure. Good thermal stability up to 250 °C was obtained. ZrPA(3:4) exhibited an ion exchange capacity of 1.04 meq g−1. At 140 °C, the proton conductivity of ZrPA(3:4) was 0.099 S cm−1 at 100% RH, 0.042 S cm−1 at 50% RH and 0.018 S cm−1 at 0RH.