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Porous boron-bearing Fe-nitrogen doped carbon electrocatalysts (Fe-BNC) are prepared by pyrolysis treatment of Fe/B co-doped zeolitic imidazolate frameworks (ZIFs). The as-obtained Fe-BNC catalysts with a high surface area (1300 m2 g−1) favor a 4-electron reduction pathway for efficient oxygen reduction reaction (ORR). The Fe-BNC catalysts demonstrate a half-wave potential of ∼0.85 V vs RHE comparable to that of Pt/C catalyst and high stability in 0.1 M KOH. The dopant of little boron and iron into nitrogen-doped carbon results in the high surface area, enhanced surface polarities, electronic properties and exposing more active sites to introduce a synergistic effect for enhanced ORR performance. Moreover, Fe-BNC electrocatalysts used as air cathode for Al-air batteries exhibit a high peak power density of 195.2 mw cm−2 and excellent stability even after discharging for 24 h at room temperature, revealing an excellent performance in application of metal-air batteries and other energy converting devices.

Fuel cell reactors can be tailored to simultaneously cogenerate value-added chemicals and electrical energy while releasing negligible CO2 emissions or other pollution; moreover, some of these reactors can even “breathe in” poisonous gas as feedstock. Such clean cogeneration favorably offsets the fast depletion of fossil fuel resources and eases growing environmental concerns. These unique reactors inherit advantages from fuel cells: a high energy conversion efficiency and high selectivity. Compared with similar energy conversion devices with sandwich structures, fuel cell reactors have successfully “hit three birds with one stone” by generating power, producing chemicals, and maintaining eco-friendliness. In this review, we provide a systematic summary on the state of the art regarding fuel cell reactors and key components, as well as the typical cogeneration reactions accomplished in these reactors. Most strategies fall short in reaching a win–win situation that meets production demand while concurrently addressing environmental issues. The use of fuel cells (FCs) as reactors to simultaneously produce value-added chemicals and electrical power without environmental pollution has emerged as a promising direction. The FC reactor has been well recognized due to its “one stone hitting three birds” merit, namely, efficient chemical production, electrical power generation, and environmental friendliness. Fuel cell reactors for cogeneration provide multidisciplinary perspectives on clean chemical production, effective energy utilization, and even pollutant treatment, with far-reaching implications for the wider scientific community and society. The scope of this review focuses on unique reactors that can convert low-value reactants and/or industrial wastes to value-added chemicals while simultaneously cogenerating electrical power in an environmentally friendly manner. Graphical Abstract A schematic diagram for the concept of fuel cell reactors for cogeneration of electrical energy and value-added chemicals

Nickel based materials are promising electrocatalysts to produce hydrogen from water in alkaline media. However, the stability is of great challenge, limiting its practical material functions. Herein, a new technique for electro-deposition flower-like NiCo

One-dimensional nanostructured CuCo2O4-Sm0.2Ce0.8O1.9 (SDC) nanofibers are prepared by the electrospinning method and one step sintering as a cathode with low polarization resistance for intermediate temperature solid oxide fuel cells (IT-SOFC). The CuCo2O4-SDC nanofibers cathodes form a porous network structure and have large triple-phase boundaries. Correspondingly, the electrochemical performance of the CuCo2O4-SDC nanofibers composite cathodes shows significantly improve, achieving the polarization resistance of 0.061 Ω cm2 and the maximum power densities of 976 mW·cm−2 at 750 °C. Thus, these results suggest that CuCo2O4-SDC nanofiber could be a highly active cathode material for IT-SOFCs.

Catalytically active cathode materials are highly desirable for the development of low-temperature solid oxide fuel cells (LT-SOFCs). In the present study, we report the performance of a high-loading Sr0.9Y0.1CoO2.5+δ (SYC10) nanoparticles (NPs) as a catalytic cathode infiltrated in Ce0.8Gd0.2O2-δ (GDC) backbones for LT-SOFCs and the use of a low-loading SYC10 NPs as a catalyst for promoting the performance of a commercial cathode. The loading and calcination temperature of SYC10 NPs were systematically optimized to achieve the lowest area-specific polarization resistance at ≤650 °C. A significant reduction in polarization resistance of commercial LSCF cathode by SYC NPs has also been demonstrated at 650 °C.

In order to design and synthesize oxygen reduction reaction catalysts with high activity and low cost, a series of Co–Mn-oxide/C catalysts with different Co:Mn ratios have been prepared using a hydrothermal method applied in sequential steps. The monotonically systematic trends of the catalysts’ phases, morphologies and particle sizes have been verified, and the trending of Mn ions and Co ions in different valence states follows the increasing Co:Mn ratio. Electrochemical performance of the catalysts in oxygen reduction reaction results in a volcano-type trend with an optimal Co:Mn ratio of 3 giving the best performance, which is comparable to that of commercial Pt/C. Lastly, a Koutecky-Levich approach has been employed to deduce the electron transfer values, in an attempt to rationalize their selectivity towards the varying 2 and 4 electron pathways. The systematic research is significant for understanding and designing a new generation of non-noble metal oxygen reduction reaction catalysts.

The oxygen reduction reaction (ORR) plays a significant role in energy conversion technologies such as metal-air batteries and fuel cells. The development of efficient ORR electrocatalyst is highly desirable to achieve the fast oxygen reduction. In this work, the bimetallic Cu and Co embedded nitrogen-doped carbon (CuCo-N/C) is fabricated as efficient electrocatalyst for ORR. The incorporation of Cu-precursor into Co-based zeolitic imidazolate frameworks (ZIF) is innovated here to synergistically enhance the activity of Co. Surprisingly, the addition of Cu can also increase the nitrogen content in the CuCo-N/C catalysts, which could generate more active sites and result in the improvement of ORR activity. The optimized CuCo-N/C catalysts exhibit superior ORR performance with a half-wave potential of 0.85 V (vs. RHE), a limiting current density of 5.61 mA cm−2 and enhanced long-term durability comparing with the state-of-the-art Pt/C catalysts. Benefiting from the unique structure, the as-made CuCo-N/C catalysts as electrode for Zn-air battery delivers excellent performance with a peak power density of 66.9 mW cm−2, a high open circuit voltage of 1.468 V, and a voltage degradation of about 1.4% after 12 h discharging, which is much better than that of Pt/C catalysts.

Proton-conducting perovskite oxides such as doped barium cerate and barium zirconate are promising electrolytes for solid oxide fuel cells (SOFCs). Multiple-doped barium cerate perovskite oxide proton conductors of BaCe0·7Zr0·1Y0.2-xNdxO3−δ (0 ≤ x ≤ 0.1) are prepared by solid state reaction and the properties of the fabricated material are characterized by various technologies. Nd doping improves the sinterability and Zr doping enhances the chemical stability in CO2 atmosphere. The electrical conductivity order of the as-prepared electrolytes at elevated temperature in hydrogen atmosphere is: BaCe0·7Y0·17Zr0.1Nd0.03O3−δ > BaCe0·7Y0·2Zr0·1O3−δ > BaCe0·7Y0·1Zr0.1Nd0.1O3−δ. Ethane is selectively dehydrogenated to ethylene with cogeneration of electrical power in the SOFC operated at 650–700 °C. The maximum power density of the SOFC is 123 mW cm−2 for ethane fuel and 138 mW cm−2 for hydrogen fuel at the 700 °C. These unique features make the multiple-doped barium cerate perovskite oxide a promising electrolyte for chemical-energy cogeneration in SOFCs.

SrCo0.7Fe0.2Zr0.1O3-δ (SCFZ) perovskite is prepared using a combustion method. SCFZ exhibits high stability while SrCo0.8Fe0.2O3-δ without Zr doping decomposes in CO2 and H2O- containing atmosphere at elevated temperature. SCFZ also displays excellent chemical compatibility with BaCe0.7Y0.2Zr0.1O3-δ (BCYZ) proton conductor. A ceramic membrane fuel cell reactor is assembled with SCFZ + BCYZ composite cathode, porous Pt anode and BCYZ electrolyte. High selective ethylene and electrical energy are co-generated from ethane in the proton conducting solid oxide fuel cell reactor.

Yttria doped strontium titanate (Y0.07Sr0.89TiO3, YST) material is synthesized using a conventional combustion method as anode for solid oxide fuel cells (SOFCs) in sulfur- and hydrocarbon-containing fuels. The YST perovskite exhibits good stability and chemical compatibility with yttria stabilized zirconia (YSZ) electrolyte in 0.5% H2S-containing fuel at high temperatures. Moreover, the YST shows high electrical conductivity of 35 S cm−1 at 900 °C and the cell with this anode achieves a maximum power density of 200, 162 and 70 mW cm−2 when the anode is fed by 0.5% H2S-containing hydrogen, syngas and methane fuels, respectively. More importantly, the cell shows negligible degradation in the sulfur-, carbon- and hydrocarbon-containing fuels. Thus, YST holds the promise as anode material for SOFCs, especially in high concentration sulfur-, carbon- and hydrocarbon-containing fuels.

This study investigates the ethane conversion in solid oxide fuel cell (SOFC) reactors, comprising a nanosized Co–Cr2O3 nanocomposite anode catalyst, a proton-conducting BaCe0.8Y0.15Nd0.05O3−δ (BCYN) electrolyte, and a porous Pt cathode, for the purpose of cogenerating value-added ethylene with high selectivity and electrical power. The Co–Cr2O3 nanocomposite anode catalyst is achieved by reducing the Co2CrO4 precursor particles of about 5 nm, by a citrate–nitrate combustion method at an elevated temperature, whereas the BCYN dense membrane is obtained by sintering the BYCN precursor powders at 1400 °C for 10 h. The protonic SOFC reactor cogenerates a maximum power density of 173 mW·cm–2 and an ethylene yield of 32% at a selectivity of 91.6% at 700 °C. More importantly, no detectable acetylene and carbon dioxide (CO2) emission are formed, suggesting the superior electrocatalytic activity and dehydrogenation activity of the Co–Cr2O3 nanocomposite for the cogeneration of ethylene and electricity.

Pt modified Pd/C catalysts were synthesized through galvanic replacement method in a one-pot synthetic process, where the replacement reaction was influenced greatly by the presence of the haloids (Cl− or Br−) in the solution. The catalysts with and without Pt modification were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-Ray spectroscopy (EDX) and electrochemical tests. The modified state and atomic ratio of Pt to Pd due to the variation of synthetic conditions were confirmed by the physical characterizations. The variation in structure/surface composition of the Pt–Pd/C catalysts leaded to different reaction mechanism and varied the performance of formic acid electrooxidation, which were confirmed by the electrochemical tests. The Pd/C catalyst modified with Pt in the presence of Cl− possesses satisfactory comprehensive performance, i.e. both stability and activity, for formic acid electrooxidation (FAEO). The results are of significance for designing catalysts for practical application of direct formic acid fuel cell and understanding mechanism of FAEO on noble metals composite structures.

A series of Pt/C catalysts with controlled Pt particle sizes is synthesized using a surfactant-free process with ethylene glycol as the weak reducing agent. The Pt particle size can be regulated by controlling the pH of the Pt (IV) complex via the addition of different amounts of urea. The results of X-ray diffraction and transmission electron microscopy confirm that the Pt nanoparticles on the carbon exhibit good size controllability and dispersion. The electroactive surface area (ESA), the electron transfer coefficient, and the electrocatalytic activity to dimethyl ether electrooxidation are dependent on the Pt particle size, and a comparison of the electrochemical properties of the samples reveals that the relationships are parabolic. The results are important for understanding the mechanism of and designing an effective catalyst for dimethyl ether (DME) electrooxidation and providing a size-controlled synthetic method for Pt-based catalysts.

H 2 -mesoporphyrin IX and Zn-mesoporphyrin IX have been investigated as sensitizers for the titanium dioxide (TiO 2 ) film electrode to construct a new two-compartment photoelectrochemical biofuel cell (PEBFC). The PEBFC can convert the light and chemical energy to electricity by consuming photons and oxidizing glucose. The two sensitizers are similar with two carboxyl anchoring groups, except that the central hydrogen atoms in the H 2 -mesoporphyrin IX are replaced by zinc. To determine how cell performance is affected by the sensitizer, we analyze the photochemical and photoelectrochemical properties of the two sensitizers by physical characterization and photoelectrochemical experiments. The UV–Vis absorption spectra and X-ray photoelectron spectra (XPS) indicate that the interactions between the sensitizer and TiO 2 decrease in the order of H 2 -mesoporphyrin IX > Zn-mesoporphyrin IX. The interactions are also determined by Fourier transform infrared (FTIR) spectra which indicate that the two sensitizers are adsorbed on the TiO 2 film through the carboxyl groups. The photovoltaic characteristics show the Zn-mesoporphyrin IX is less effective in comparison with the H 2 -mesoporphyrin IX, since the Zn-mesoporphyrin IX enhances the back electron-transfer process, producing lower IPCE and current. These results reveal that the H 2 -mesoporphyrin IX is a more efficient sensitizer compared with the Zn-mesoporphyrin IX for the PEBFC.

Two types of Pt nanowires (NWs)/C catalysts with different aspect ratios and one type of Pt nanoparticles/C catalyst are successfully synthesized, and DME electrochemical performance on different extent consecutive surfaces is investigated. The morphology and crystallization are confirmed with electron microscopes and XRD. The electrochemical tests show that the nanowire catalysts, especially the one with higher aspect ratio, possess higher electrochemical surface areas, higher absorption capacity of DME, higher CO tolerance, higher electron transfer coefficient, and higher activity towards DME electrooxidation than those of the nanoparticle catalyst. The results prove that the consecutive surface favors for direct dimethyl ether fuel cell (DDFC) anodic catalyst, which are contributive to the study of the mechanism of DME electrooxidation on Pt surface and designing an effective catalyst for anodic DDFC.

PtPd/C catalysts with different surface compositions (Pt + Pd, Pt–Pd and Pd–Pt) were synthesized with different deposition sequences, and characterized by electrochemical experiments and XPS measurements. The different catalytic characteristics for formic acid electrooxidation occurred on the three PtPd/C catalysts were preliminarily discussed according to the oxidation pathway. Due to the synergistic effect between Pt and Pd, especially for Pt + Pd, the catalytic stability for formic acid oxidation was greatly increased. The results are helpful in preparing of PtPd catalyst and understanding the oxidation mechanism for formic acid oxidation.

The methanol electro-oxidation behaviors on the Pt-MoOx/C catalysts with various compositions were investigated and compared to those of Pt/C catalyst by cyclic voltammetry and chronoamperometry The Pt-MoOx/C catalysts were prepared by depositing Pt on the MoOx/C support obtained by precipitation-reduction method in advance The physical properties of the prepared catalysts were characterized by XRD XPS EDX and TEM From the results of XRD and TEM it was shown that the MoOx/C support facilitated the dispersion of Pt particles All the Pt-MoOx/C catalysts showed relative lower Mo contents comparing to their nominal values No PtMo alloy was formed in these catalysts which were affirmed by XPS and XRD It was found that all the Pt-MoOx/C catalysts showed higher mass activity (normalized to the mass of Pt) but lower specific activity (normalized to the electrochemical active surface areas) for methanol oxidation than the Pt/C catalyst With the increase of Mo contents in Pt-MoOx/C catalysts the activities of Pt-MoOx/C catalysts decreased Combined with the composition and structure analyses the differences in methanol oxidation on these catalysts were attributed to the interaction between the Pt particles and the MoOx/C support It was suggested that the Pt metal-MoOx/C support interaction resulted in two effects One was decreasing the Pt particle size the other was decreasing the specific activities of these catalysts for methanol oxidation Comprising these two contradictory effects the mass activities of these catalysts for methanol oxidation increased (C) 2010 Elsevier Ltd All rights reserved

Development of high-efficiency and cost-effective carbon capture technology is a central element of our effort to battle the global warming and climate change. Here we report that the unique high-flux and high-selectivity of electrochemical silver-carbonate dual-phase membranes can be retained for an extended period of operation by overcoating the surfaces of porous silver matrix with a uniform layer of Al2O3 thin-film derived from chemical vapor deposition.

High-loading carbon supported Pt nanowire electrocatalysts are successfully synthesized in a mild one-pot template- and surfactant-free route. The high electrocatalytic activity, Pt utilization, and long-term stability toward methanol are ascribed to the anisotropic structural properties, exposure of specified planes, and the role of support on good dispersion.

In this chapter, the fundamentals of oxygen reduction reaction (ORR) including thermodynamics and electrode kinetics are presented. The ORR kinetics including reaction mechanisms catalyzed by different electrode materials and catalysts including Pt, Pt alloys, carbon materials, and nonnoble metal catalysts are discussed based on the literature in terms of both experiment and theoretical approaches. It is emphasized that these fundamentals of ORR are necessary in order to perform the meaningful characterization of catalytic ORR activity using both rotating disk electrode and rotating ring-disk electrode methods.

1. Introduction High temperature (HT) operation at 800 – 1000 °C causes many problems such as the thermal mismatch between membrane electrode assembly (MEA) components, expensive bipolar plates, micro structural changes, inter-diffusions, slow start-up time, decreasing system power density due to heat insulators. In order to overcome this main commercialization obstacle of solid oxide fuel cells (SOFCs), a lot of intermediate temperature (IT) electrolyte materials (Doped ceria, LSGM, ScSZ and so on) which can substitute for conventional YSZ have been proposed. And various thin film deposition techniques (Screen printing, Dip-coating, Magnetron sputtering, Pulsed Laser Deposition, Chemical Vapor Deposition and Atomic Layer Deposition) were applied to this research field. The goal of both types of approaches is minimizing the ionic resistance at decreased temperature. Recently, the sodium doped strontium silicate (Sr1-xNaxSiO3-0.5x) is gathering attentions as a fast ion conductor.[1] And Wei et al. confirmed a good SOFC performance using this electrolyte material at 500 and 600 °C. [2] In this study, we investigated on this promising material to get the optimal fabrication conditions with composition and to minimize several problems on this material. 2. Experimental The starting raw powders of SrCO3 (Sigma-Aldrich 99.9%), Na2CO3 (Alfa Aesar, 99.9%) and SiO2(Alfa Aesar 99.9%) were mixed and ball milled. The Na doping percentages on strontium site were 0 to 100 %. We varied calcination temperature from 600 °C to 1000 °C. After ball milling step, we also varied sintering temperature (800 – 1150 °C) and time (10, 20 and 100 h). Conductivity tests were conducted in the air environment and the furnace was controlled from 400 to 750 °C. Sample pellet was prepared to get the thickness of 1.5 mm using low speed saw. Then, we pasted silver electrodes with current collecting meshes on both sides of pellets and connected wires to electrochemical impedance spectrometer (Solartron 1287 and 1260, UK). The micro structural images were captured using a field emission scanning electron microscope (FESEM, Zeiss Ultra) equipped with an energy dispersive X-ray spectroscopy (EDS) analyzer, respectively. The phase check was done using an X-ray diffractometer (D/max-A, Rigaku, Japan) with CuKα radiation (λ=1.5418 Å). The scan range was 2θ = 10 – 70 °at a rate of 5 ° min-1. From this study, we found out the optimal fabrication conditions (sintering at 900 °C for 10 h) for 45 % sodium doped strontium silicate electrolyte which was known as the best ionic conductor. Moreover, we could guess the origin of this high conductivity was from the amorphous sodium silicate. Reference [1] P. Singh and J. B. Goodenough, J. Am. Chem. Soc., 2013, 135, 10149–10154 [2] T. Wei, P.Singh, Y. Gong, J.B. Goodenough, Y. Huang and K. Huang, Energy Environ. Sci., 2014, 7, 1680-1684 Figure 1

We developed a method to significantly decrease the methanol permeability of a Nafion membrane that does not require sacrificing its proton conductivity and mechanical stability. The Nafion membrane modified by the coating of a thin layer of sulfonated organic silica on the membrane surface exhibits significantly decreased methanol permeability--the permeability is decreased to an undetectable level--while retaining an acceptable ionic conductivity of 0.029 S cm(-1).