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Nickel hydroxide (Ni(OH)2) is one of the most attractive electrode materials for supercapacitor applications due to its intrinsically high redox capacitance. However, the electrochemical performanc...

In this work, the anion in situ doped nickel hydroxide nanoparticles were electrochemically synthesized by different nickel salt solution. NO3−, Cl− and SO42− can be in situ intercalated into the cathodically deposited Ni(OH)2 sample (α-phase), while CH3COO− cannot be in situ intercalated into the cathodically deposited Ni(OH)2 sample (β-phase). The doping effect on the electrochemical performances of the synthesized sample is related with both of the size and the structure characteristic of the doped anions. On one side, the enlargement of lattice spacing is beneficial to H+/OH− transfer, and on the other side, the steric hindrance effect is restrictive to H+/OH− transfer. However, the NO3− intercalated Ni(OH)2 sample has the largest lattice spacing and the highest electrochemical performances due to its special planar structure characteristic and the effect on the dissociation energy of O-H bond in the charge-discharge process of Ni(OH)2.

Reduced graphene oxide (rGO)-modified copper foil composite material was prepared by electrocoagulation of graphene oxide (GO) and a subsequent chemical reduction process. The effects of deposition voltages and the reduction time on the morphology, structure and electrochemical performances of the sample are investigated. The uniform surface morphology of GO/Cu sample obtained at a deposition voltage of 2.5 V. However, the appropriate chemical reduction not only improves the electrical conductivity of GO/Cu, but also enhances anticorrosion performance. At the optimized deposition voltages (2.5 V) and reduction time (20 min), the rGO/Cu shows the highest anticorrosive property and good conductivity. The protective efficiency of rGO/Cu is up to 98% (vs bare copper) as compared with 60% of GO/Cu according to Tafel analyses. The conductivity of rGO/Cu is close to bare copper according to the electrochemical impedance spectroscopy (EIS) results of Ni(OH)2/rGO/Cu and measurement of surface resistivity. We consider that rGO/Cu is a suitable material for realizing the copper foil manufacture with high corrosion resistance without sacrificing conductivity.

In this study, α-Ni(OH)2 with controllable pristine crystal size is directly electrodeposited on a substrate of Ti wire mesh to fabricate the integrated electrode. The nanoscale effects on morphology, microstructure and electrochemical performance of the cathodic deposited α-Ni(OH)2 are studied. The results show that the morphology of α-Ni(OH)2 varies from irregular honeycomb-like nanopieces, ball-shaped particles to oval nanoplates as the cathodic deposition current density increases. The nanostructure diversity of the cathodic deposited α-Ni(OH)2 is due to the different nanosize which directly depends on the cathodic deposition current density. The electrochemical performances of the cathodic deposited α-Ni(OH)2 increase with the decrease of the pristine crystal size of α-Ni(OH)2. The oval α-Ni(OH)2 nanoplates consisting of nanosheets with a pristine crystal size of 3 ∼ 5 nm × 5 ∼ 7 nm show the ultrahigh specific capacities of ∼348 mAh g−1 and ∼312.5 mAh g−1 at charge/discharge current density of 5 A g−1 and 100 A g−1, respectively, and over 70% specific capacity still remains after 1000 cycles, while the irregular honeycomb-like α-Ni(OH)2 consisting of nanosheet with a pristine crystal size of 10 ∼ 15 nm × 15 ∼ 20 nm shows only ∼260 mAh g−1 specific capacity at 5 A g−1 and ∼150 mAh g−1 at 100 A g−1. The ultrahigh electrochemical performances are attributed to the nanoscale and the defective nanostructure of the cathodic deposited α-Ni(OH)2.

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeCx nanoparticles and porous carbon composited catalyst (Fe/FeCx@NC) via a facile two-step heat treatment strategy. The Fe/FeCx@NC-800−0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeCx@NC-T−t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeCx@NC-800−0.5 is caused by the synergistic effect between Fe/FeCx core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.

Si/C materials are considered as the most promising anodes for the next generation lithium ion batteries. However, the Si/C anodes with high Coulombic efficiency are still a challenge. Here, pomegranate-like Si@C microspheres are successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization and acid etching processes. As high as 84.98% initial Coulombic efficiency (ICE) and 100% Coulombic efficiency are obtained for the sample (Si40@C3), and the specific capacity still maintained over 620 mAh g−1 with capacity retention of 70.4% over 250 cycles. The excellent electrochemical performance could be attributed to the distinctive pomegranate-like Si@C structure, which either stabilizes the porous structure of Si particle by inhibiting the volume expansion and pulverization or improves the electrochemical property by the appropriate carbon coating layer. This would provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling.

Iron and nitrogen co-doped carbon (Fe-N/C) materials were fabricated by one-step pyrolysis of the mixture of FeCl3 and the low-cost biomass soybeans in N2 atmosphere at different temperatures. The physical properties of the prepared Fe-N/C catalysts were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) et al., the catalytic activity and stability of the Fe-N/C catalysts toward the oxygen reduction reaction (ORR) in alkaline solution were investigated by the electrochemical techniques. The results show that Fe is mainly in the form of Fe3O4 with the particle size of about 10 nm and encapsulated by thin graphite layers, and the content of Fe decreases from 1.19 to 0.24 wt.% with the increase of pyrolysis temperature from 600 to 900 °C. The ORR activity on the sample prepared at 700 °C (Fe-N/C-700) is preferable among the series of Fe-N/C catalysts, with the half-wave potential of the ORR shifting negatively only about 0.020 V as compared to that on the commercial Pt/C (40 wt.%, JM). The superior electro-catalytic performance of the Fe-N/C-700 catalyst would be due to the higher degree of the graphitization, the higher total contents of the pyridinic-N, quaternary-N/graphitic-N, as well as the relatively higher Fe3O4 content and surface area. The electron transfer number of the ORR on the Fe-N/C-700 catalyst approaches four indicating the 4-electron transfer pathway. Besides, the methanol tolerance and durability are superior to those on the Pt/C.

The concept of aqueous solution Al-ion battery inspires much enthusiasm in developing a novel chemical power source. In this work, the electrochemical behavior of TiO2-NTAs electrode in Al3+aqueous solution with different acidity is evaluated. Electrochemical studies showed that both of H+ and Al3+ in aqueous solution are electrochemical active to TiO2-NTAs, however, H+ is preferential to hydroxylate on the TiO2-NTAs surface rather than to intercalate in the TiO2-NTAs lattice as compared with Al3+under the assistance of Cl−. The surface hydroxylation of TiO2-NTAs can retard Al3+ diffusion in the TiO2-NTAs lattice as evidenced by the increase of faradic resistance RF (by EIS) at initial cathodic polarization process, however, the subsequent decrease of RF is due to the conductance improvement of TiO2-NTAs with the Al3+ intercalation. Here it can be concluded that for Al3+ aqueous solution battery with TiO2-NTAs as electrode, the suitable acidity (pH≈3) is required to minimizing the effect of H+.

Highly ordered TiO 2 nanotube arrays (NTAs) with excellent stability and large specific surface area make them competitive using as supercapacitor materials. Improving the conductivity of TiO 2 is of great concern for the construction of high-performance supercapacitors. In this work, we developed a novel approach to improve the performance of TiO 2 materials, involving the fabrication of Al-doped TiO 2 NTAs by a simple electrochemical cathodic polarization treatment in AlCl 3 aqueous solution. The prepared Al-doped TiO 2 NTAs exhibited excellent electrochemical performances, attributing to the remarkably improved electrical conductivity (i.e., from approx. 10 kΩ to 20 Ω). Further analysis showed that Al 3+ ions rather than H + protons doped into TiO 2 lattice cause this high conductivity. A MnO 2 /Al–TiO 2 composite was evaluated by cyclic voltammetry, and achieved the specific capacitance of 544 F g −1 , and the Ragone plot of the sample showed a high power density but less reduction of energy density. These results indicate that the MnO 2 /Al–TiO 2 NTAs sample could be served as a promising electrode material for high -performance supercapacitors.

Magneli phase titanium sub-oxide conductive ceramic Ti n O2n−1 was used as the support for Pt due to its excellent resistance to electrochemical oxidation, and Pt/Ti n O2n−1 composites were prepared by the impregnation-reduction method. The electrochemical stability of Ti n O2n−1 was investigated and the results show almost no change in the redox region after oxidation for 20 h at 1.2 V (vs NHE) in 0.5 mol/L H2SO4 aqueous solution. The catalytic activity and stability of the Pt/Ti n O2n−1 toward the oxygen reduction reaction (ORR) in 0.5 mol/L H2SO4 solution were investigated through the accelerated aging tests (AAT), and the morphology of the catalysts before and after the AAT was observed by transmission electron microscopy. At the potential of 0.55 V (vs SCE), the specific kinetic current density of the ORR on the Pt/Ti n O2n−1 is about 1.5 times that of the Pt/C. The LSV curves for the Pt/C shift negatively obviously with the half-wave potential shifting about 0.02 V after 8000 cycles AAT, while no obvious change takes place for the LSV curves for the Pt/Ti n O2n−1. The Pt particles supported on the carbon aggregate obviously, while the morphology of the Pt supported on Ti n O2n−1 remains almost unchanged, which contributes to the electrochemical surface area loss of Pt/C being about 2 times that of the Pt/Ti n O2n−1. The superior catalytic stability of Pt/Ti n O2n−1 toward the ORR could be attributed to the excellent stability of the Ti n O2n−1 and the electronic interaction between the metals and the support.

A series of PdO/C catalysts were prepared by using the PdCl2 and Mn3O4/C as the precursors. The physical properties and the catalytic activity toward the oxygen reduction reaction (ORR) in alkaline media of the prepared PdO/C catalysts were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), as well as transmission electron microscopy (TEM) and the electrochemical techniques. The results show that, with the reaction time increasing, the main species PdO forms on the surface of carbon accompanied by a decreasing of the Mn content, implying a replacement of Mn3O4 with PdO on the carbon surface. The morphology of the irregular aggregates composed of PdO nanoparticles (about 2.3 nm) is similar to that of Mn3O4 particles. The PdO/C catalyst with the reaction time of 4 h and the Mn content of 0.03 wt.% (PdO/C-4 h) exhibits the highest activity toward the ORR, with the onset potential and the half-wave potential of the ORR shifting positively about 0.017 V and 0.020 V, respectively, compared to those on the commercial Pd/C (20 wt. %, E-TEK). The specific and mass current densities for he ORR obtained at 0.850 V (vs. RHE) on the PdO/C-4 h catalyst are about 2.64 mAcm(Pd) (2) and 1.11 mA mu g(Pd) (1), respectively, being about 2.67 and 2.18 times to those on the Pd/C. After 2000 potential cycles between 0.424 V and 1.124 V for accelerated aging tests, the better catalytic stability of the PdO/C-4 h catalyst toward the ORR over the Pd/C is observed, with the half-wave potential of the ORR shifting negatively only about 0.013 V, less than that on the latter one. All these findings demonstrate that the catalytic activity and stability of PdO/C-4 h catalyst for the ORR are superior to those of the commercial Pd/C, and the PdO/C-4 h catalyst would be a promising candidate for the non-platinum catalysts in alkaline media. (C) 2014 Elsevier Ltd. All rights reserved.

The titanium dioxide nanotube array (TiO2-NTA) is prepared by a two-step anodic oxidation method and annealed at 450 ∘C subsequently. The Al-inserted TiO2-NTA is prepared by polarizing the TiO2-NTAs electrode at 0.4 mA for 2 min in 1 mol/L AlCl3. The results show that the Al-inserted sample still remains pure anatase TiO2 phase (by XRD) and keeps intact nanotube array structure (by FE-SEM). The X-ray photoelectron spectroscopy (XPS) analysis indicates that the insertion of Al3+ into TiO2-NTAs facilitates in the reduction of Ti4+ to Ti3+. Electrochemical investigation on the Al3+ insertion process reveals that presence of Cl− ions plays vital role for the effective insertion and de-insertion of Al3+ into/from the TiO2-NTA.

Ag-MnOx/C composites were prepared using AgNO3 and KMnO4 as the precursors and Vulcan XC-72 as the support. The physical properties of the Ag-MnOx/C composites were investigated via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The activity and the stability of the series of Ag-MnOx/C composites toward the oxygen reduction reaction (ORR) in alkaline media were investigated through the electrochemical techniques. The results show that the main species MnO2 and Ag2O in the fresh sample convert into Mn3O4 and Ag(0), respectively, after the heat treatment in N2 at 300 °C (Ag-MnOx/C-300). The Ag-MnOx/C-300 sample shows the highest activity toward the ORR, with the half-wave potential of the ORR shifting negatively only 0.035 V compared to that on the commercial 40 wt. % Pt/C (JM). The electron transfer number during the ORR on the Ag-MnOx/C composite increases with the value close to four after the heat treatment at 300 °C, which is mainly attributed to the formation of Ag(0), rather than Mn3O4. The heat treatment brings about a better catalytic stability of the composite, and no obviously negative shift takes place for the half-wave potential of the ORR on the Ag-MnOx/C-300 composite after 1000 cycles accelerated aging test. The maximum power density of the zinc-air battery with the Ag-MnOx/C-300 air electrode reaches up to 130 mW cm−2, higher than those based on the Pd/C and Pt/C cathode catalysts, which shows that the Ag-MnOx/C-300 composite is a promising candidate as the catalyst for the air electrode.

A series of Ni modified MnOx/C composites were synthesized by introducing NaBH4 to MnO2/C aqueous suspension containing Ni(NO3)2. The physical properties and the activity of the composites toward the oxygen reduction reaction (ORR) were investigated via transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and the electrochemical techniques. The results show that the higher activity of the composites toward the ORR is correlated with the higher content of MnOOH species transformed from Mn(II) on the surface of the composite. The main nickel species in the composites is Ni(OH)2, while Ni(OH)2 shows little activity toward the ORR. However, introducing Ni(OH)2 with proper amount into the MnOx/C improves the distribution of the active material MnOx, which contributes to a surface with more MnOOH. The optimal composite is of the Ni/Mn atomic ratio of 1:2 and the MnOx loading of 28 wt.%. The maximum power density of the zinc–air battery with the optimized Ni modified MnOx/C as the cathode catalyst reaches up to 122 mW cm−2, much higher than the one with the MnOx/C as the air cathode catalyst (89 mW cm−2), and slightly higher than those with the Pd/C and Pt/C as the cathode catalysts.

In this work, we successfully synthesized Ni(OH)2 thin film electrode in situ doped with CNTs/rGO by cathodic electrodeposition on titanium mesh. The doping effects of CNTs and/or rGO, and the technical conditions, are investigated. The doping of CNTs/rGO can greatly improve the electrochemical performance by forming the porous structure and the conductive network in the Ni(OH)2 thin film. The highest capacity, 429.5 mAh/g at a current density of 5 A/g, is achieved for the electrode with 0.24 mg/cm2 Ni(OH)2 and codoped with CNTs and rGO, as compared with only 323.9 mAh/g for undoped electrode. Even at 100 A/g, the specific capacity can still remain 347.5 mAh/g (vs. 221.5 mAh/g for the undoped electrode), and after 1000 cycles, the retention rate of the specific capacity is 74.9% as compared with only 42.7% for the undoped electrode. Even with higher loading amounts of 1.92 mg/cm2 Ni(OH)2, the specific capacity retention rate of the codoped electrode is still much higher than that of the undoped electrode. The high electrochemical performance can be attributed to the better ion/electron transfer ability of the codoped electrode. In conclusion, by the cathodic electrodeposition and in situ doping of CNTs/rGO, the porous structure and the conductive network in Ni(OH)2 film can be constructed, which can improve the ion/electron transfer ability, therefore, the high performance film electrode with higher loading amount of Ni(OH)2 can be prepared.

The Magneli phase titanium sub-oxides conductive ceramic particles were added to Zn electrodes for use in Ni/Zn batteries. X-ray diffraction analysis indicated that the basis of the conductive ceramic was Ti4O7 and transmission electron microscopy showed that the particles were uniform in shape and size. The electrochemical performance of a Zn electrode with the conductive ceramic as the conductive additive was investigated by charge/discharge cycling test, cyclic voltammetry, and Tafel plot. Compared with a Zn electrode with acetylene black and without conductive additive, the electrode with conductive ceramic showed better cycling stability, higher discharge capacity, and corrosion resistance.

A novel composite alkaline polymer electrolyte based on poly(vinyl alcohol) (PVA) polymer matrix, titanium dioxide (TiO2) ceramic fillers, KOH, and H2O was prepared by a solution casting method. The properties of PVA–TiO2–KOH alkaline polymer electrolyte films were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and AC impedance techniques. DSC and XRD results showed that the domain of amorphous region in the PVA polymer matrix augmented when TiO2 filler was added. The SEM result showed that TiO2 particles dispersed into the PVA matrix although some TiO2 aggregates of several micrometers were formed. The alkaline polymer electrolyte showed excellent electrochemical properties. The room temperature (20 °C) ionic conductivity values of typical samples were between 0.102 and 0.171 S cm−1. The Zn–Ni secondary battery with the alkaline polymer electrolyte PVA–TiO2–KOH had excellent electrochemical property at the low charge–discharge rate.

Hydroxyapatite (HA) was selected as dopant and synthesized by a sonochemical method in this study. PVA–HA–KOH–H 2 O composite alkaline solid polymer electrolyte (ASPE) was prepared by solution casting method. Two different doping routes, i.e., the physical mixing (PM) and in situ synthesis (ISS) were considered. The influences of the ASPE composition such as HA content, KOH content and water content on the conductivity were investigated. The ASPE prepared by ISS route has a porous structure which is important for ion transfer. Accordingly, the conductivity of the ASPE prepared by ISS is higher than that of by PM. A highest conductivity of about 0.1 S/cm is reached for ASPE prepared by ISS route at 70% water content for m (PVA): m (KOH): m (HA) = 10:14:10 system, higher than that of by PM route, 0.08 S/cm. The nickel/zinc cell shows better electrochemical properties assembled with the ASPE prepared by ISS approach than by PM approach.

The influence of the dopant Bentonite, on the ionic conductivity of the PVA-KOH-H 2 O alkaline solid polymer electrolyte (ASPE) is studied. The results show that the addition of Bentonite has both positive and negative effects on the ionic conductivity of ASPE. At lower KOH and H 2 O contents, the addition of Bentonite can break the continuous ion conducting phase of the ASPE, and therefore decrease the ASPE conductivity. However, the addition of Bentonite can also increase the KOH content in PVA matrix. This greatly increases the conductivity of the ASPE especially at higher water content. A highest ionic conductivity of 0.11 S cm −1 is reached at room temperature. A maximum ionic conductivity value is observed at relative lower water content for different amount of Bentonite-doped ASPE. The temperature dependence of the ionic conductivity is of the Arrhenius type. The ion transfer activation energy Ea , in the order of 4–6 kJ mol −1 , heavily depends on the Bentonite content. XRD and SEM tests show that PVA in the Bentonite-doped ASPE is of amorphous structure, and there are lots of interspaces in the composite ASPE inner structure. The composite electrolyte has good electrochemical stability window and good charged–discharge property in secondary Zn–Ni cells at low charge–discharge rate.

A novel gel of imidazole/(HPO3)3 was synthesized and incorporated into sulfonated poly (ether ether ketone) (SPEEK) to fabricate composite proton exchange membranes. The composite membranes were characterized by alternating current impedance (AC), thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscope (SEM) and mechanical property test. Based on the electrochemical performance investigation, the proton conductivity of the membrane is intimately correlated with the temperature and the mass ratio of imidazole/(HPO3)3 in the composite. The SPEEK/imidazole/(HPO3)3−4 composite membrane (with 44.4 wt % of imidazole/(HPO3)3) has the optimized performance at 135°C. Mover, the strength of the composite membranes is almost comparable to that of Nafion membrane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41946.