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The mechanism of the dioxygen interaction with and reduction reaction at iron α,β,γ,δ-tetra(4-pyridyl) porphyrin (FeTPyP) deposited on carbon and silver supporting electrodes was investigated with cyclic voltammetry and FTIR, UV-vis and resonance Raman spectroscopies. Results indicate a strong influence of the ligand upon the reduction electrocatalysis. Spectroelectrochemical results support a two-electron pathway resulting most probably in hydrogen peroxide as the primary reduction product.

The mode of interaction with and the mechanism of the dioxygen reduction reaction at six transition metal α,β,γ,δ-tetra(4-pyridyl)porphyrins (MeTPyPs) deposited on carbon and silver supporting electrodes were investigated with cyclic voltammetry, FTIR and UV-vis spectroscopy and resonance Raman spectroscopy. Results indicate a strong influence of both the ligand and the central metal ion upon the reduction electrocatalysis in terms of electrode overpotentials. Spectroelectrochemical results support a two-electron pathway resulting in hydrogen peroxide as the primary reduction product. A significant influence of the central ion on the vibrational behaviour and the dioxygen reduction mechanism was not found.

This paper deals with various energy converters, in particular thermal or chemical engines and fuel cells. Applying a general thermodynamic framework we derive formulae for converters' efficiencies and apply them to estimate power limits in these power systems. We consider power limits for thermal systems propelled by differences of temperatures and chemical or electrochemical systems driven by differences of chemical potentials. We focus on fuel cells which are the electrochemical energy generators. We show that fuel cells satisfy the same modeling principles as thermal machines and apply similar computational schemes.

The world’s challenge is to determine a more efficient, economical and environmental-friendly energy source to compete and replace the ongoing conventional energy resources. Solid oxide fuel cells (SOFCs) provide a highly efficient system to use divergent energy resources and have proved to provide the cleanest energy, least energy use, and lowest emissions. A techno-economic study is required to investigate the model design for SOFC-based micro-combined heat and power (m-CHP) systems for applications in terms of educational and commercial buildings. This work models and explores the optimized application of hydrogen gas-fueled SOFC-based m-CHP systems in educational buildings. Two educational departments’ loads are presented and model of SOFC-based m-CHP system against the different electric power demands is performed, in order to provide a techno-economic assessment of the technology. For successful development of the technology, results are related to system rightsizing, operating strategies, thermal to electric ratios, and match between end-use, with an aim towards classifying the overall feasibility and essential application requirements.

The SOFC interconnect materials La${}_{0.75}$Sr${}_{0.25}$Cr${}_{1-x}$O${}_{3-\delta }$$(x=0$–$0.04)$ were prepared using an auto-ignition process. The influences of Cr deficiency on their sintering, thermal expansion and electrical properties were investigated. All the samples were pure perovskite phase after sintering at 1400${}^{\circ }$C for 4 h. The cell volume of La${}_{0.75}$Sr${}_{0.25}$Cr${}_{1-x}$O${}_{3-\delta }$ decreased with increasing Cr deficient content. The relative density of the sintered bulk samples increased from 93.2% $(x=0)$ to a maximum value of 94.7% $(x=0.02)$ and then decreased to 87.7% $(x=0.04)$. The thermal expansion coefficients of the sintered bulk samples were in the range of $10.60$–$10.98\times 10^{-6}{\mathrm{\text{K}}}^{-1}$ (30–1000${}^{\circ }$C), which are compatible with that of YSZ. Among the investigated samples, the sample with 0.02 Cr deficiency had a maximum conductivity of 40.4 Scm${}^{-1}$ and the lowest Seebeck coefficient of 154.8 $\mu$VK${}^{-1}$ at 850${}^{\circ }$C in pure He. The experimental results indicate that La${}_{0.75}$Sr${}_{0.25}$Cr${}_{0.98}$O${}_{3-\delta }$ has the best properties and is much suitable for SOFC interconnect material application.

Three different types of current-collecting plates for air-hydrogen PEM fuel cell were manufactured and tested: unmodified titanium plates; gold-plated titanium plates and titanium plates treated by carbon ions implantation. It was shown that the applied surface modifications reduce contact resistance between titanium plate and carbon gas diffusion layer. Total ohmic resistance of fuel cell is reduced by 1.8 and 1.4 times in case of gold-plated titanium and carbon-implanted titanium, respectively, in comparison with uncoated titanium. Although gold plating turned out to be more profitable than carbon ion implantation in terms of electrical characteristics, in the last case, the performance enhancement was reached without using precious metals, which at mass production must play more important role. This technology promises to reduce the cost of bipolar plates manufacturing, while maintaining high electrical performance of PEM fuel cells.

Self-organized TiO₂ nanotubes/titanium substrate modified with palladium nanoparticles (Pd/TiO₂/Ti electrodes) were prepared by a two-step process consisting of anodizing of titanium plate followed by electroless plating of palladium on resulted TiO₂ nanotubes. The morphology and surface analysis of Pd/TiO₂/Ti electrodes were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The results indicated that palladium nanoparticles were homogeneously deposited on the surface of TiO₂ nanotubes. The electro-catalytic activity of Pd/TiO₂/Ti electrodes in the methanol electro-oxidation was studied by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) methods. The results indicate that Pd/TiO₂/Ti electrode improve the electro-catalytic activity for methanol oxidation greatly and confirmed the better electro-catalytic activity and stability of these new electrodes. So, the Pd/TiO₂/Ti electrodes have a good application potential to fuel cells.

Apart from long-known and applied nanostructures like carbon black for tyres or pigments for coatings nanotechnology has created highly sophisticated structures used for nano/molecular electronics, diagnostics, drug delivery, UV-absorbers etc. Often the main question to be solved analytically is the local determination of tiny amounts of chemicals resulting in an ever increasing need for highly sensitive as well as locally resolved techniques. Applications of techniques like mass spectroscopy, transmission electron microscopy as well as ultracentrifugation to problems arising from nanotechnology in the chemical industry will be described.

The dicobalt complex [Co₂(L²)] of a Schiff-base pyrrole macrocycle adopts a Pacman structure in solution and the solid state and shows much greater catalytic activity and selectivity for the four-electron oxygen reduction reaction (ORR) than the mononuclear cobalt phthalocyanine (CoPc) counterpart. Soft X-ray absorption spectroscopy (XAS) shows that the Co center in Co₂(L²) is of the same valence as mononuclear CoPc. However, the former complex shows higher unoccupied Co 3d density which is believed to be beneficial for electron transfers. Furthermore, the XAS data suggests that the crystal fields for Co₂(L²) and CoPc are different, and that an interaction remains between two Co atoms in Co₂(L²). DFT calculations imply that the sterically hindered, cofacial structure of the dicobalt complex is critical for the operation of the four-electron reaction pathway during the ORR.

The objective of this investigation is to evaluate a series of polymer electrolyte membrane materials based on sulfonated ladder pyridine polymers and SiO₂ nanoparticles that enhance water retention and favor high temperature (> 120°C) applications. Nanoparticles are used to improve water uptake at levels of 20–38% to increase the level of sulfonation. A study of relevant characteristics of these polymers will provide an alternative to existing polymers, thus offering simple processing steps, as well as nonexotic polymers and higher performances.

Cobalt-Chrome nanoparticles-incorporated carbon nanofibers (CNFs) are proposed as an effective nonprecious electrocatalyst for methanol oxidation in the alkaline media. The introduced nanofibers were prepared by simple technique, electrospinning. Carbonization of as-spun mat composed of chromium acetate, cobalt acetate and poly(vinyl alcohol) (PVA) at high temperature (900${}^{\circ }$C) leads to production of the introduced nanofibers. The physicochemical characteristics were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) equipped with EDX and TEM mapping. The exploited analyses confirmed that the final product is in the form of CNFs decorated by Co/Cr nanoparticles. Based on the results obtained from the cyclic voltammetry (CV) measurements, the proposed Co/Cr-incorporated CNFs possess high electrocatalytic activity toward methanol electrooxidation as a clear peak of methanol oxidation appeared with corresponding current density of 56mA/cm². Moreover, the current density increased by increasing methanol concentration up to 4.0M. Overall, the proposed nanofibers open new avenue for platinum-free and stable nanostructural catalysts for fuel cell technology.

The yolk-shell Fe₃O₄-polyaniline for decoration of Pd-Ni nanoparticles (yolk-shell Fe₃O₄-PANI/Pd-Ni) were synthesized and used as a new electrocatalyst for oxidation of formic acid. The yolk-shell Fe₃O₄-PANI/Pd-Ni catalyst provided superior catalyst performance for formic acid oxidation in H₂SO₄ aqueous solution. These yolk-shell Fe₃O₄-PANI/Pd-Ni catalysts were found to be more resistant to deactivation in the oxidation of formic acid than yolk-shell Fe₃O₄-PANI/Pd and Pd/C and to consistently show better long-term performances. The enhanced catalytic performance may arise from the unique structure and surface properties of the yolk-shell Fe₃O₄-PANI and bi-functional effect, which process extraordinary promotional effect on Pd catalyst.

Bioconvection has shown significant promise for environmentally friendly, sustainable “green” fuel cell technologies. The improved design of such systems requires continuous refinements in biomathematical modeling in conjunction with laboratory and field testing. Motivated by exploring deeper the near-wall transport phenomena involved in bio-inspired fuel cells, in the present paper, we examine analytically and numerically the combined free-forced convective steady boundary layer flow from a solid vertical flat plate embedded in a Darcian porous medium containing gyrotactic microorganisms. Gyrotaxis is one of the many taxes exhibited in biological microscale transport, and other examples include magneto-taxis, photo-taxis, chemotaxis and geo-taxis (reflecting the response of microorganisms to magnetic field, light, chemical concentration or gravity, respectively). The bioconvection fuel cell also contains diffusing oxygen species which mimics the cathodic behavior in a proton exchange membrane (PEM) system. The vertical wall is maintained at iso-solutal (constant oxygen volume fraction and motile microorganism density) and iso-thermal conditions. Wall values of these quantities are sustained at higher values than the ambient temperature and concentration of oxygen and biological microorganism species. Similarity transformations are applied to render the governing partial differential equations for mass, momentum, energy, oxygen species and microorganism species density into a system of ordinary differential equations. The emerging eight order nonlinear coupled, ordinary differential boundary value problem features several important dimensionless control parameters, namely Lewis number (Le), buoyancy ratio parameter i.e. ratio of oxygen species buoyancy force to thermal buoyancy force (Nr), bioconvection Rayleigh number (Rb), bioconvection Lewis number (Lb), bioconvection Péclet number (Pe) and the mixed convection parameter ($𝜀)$ spanning the entire range of free and forced convection. The transformed nonlinear system of equations with boundary conditions is solved numerically by a finite difference method with central differencing, tridiagonal matrix manipulation and an iterative procedure. Computations are validated with the symbolic Maple 14.0 software. The influence of buoyancy and bioconvection parameters on the dimensionless temperature, velocity, oxygen concentration and motile microorganism density distribution, Nusselt, Sherwood and gradient of motile microorganism density are studied. The work clearly shows the benefit of utilizing biological organisms in fuel cell design and presents a logical biomathematical modeling framework for simulating such systems. In particular, the deployment of gyrotactic microorganisms is shown to stimulate improved transport characteristics in heat and momentum at the fuel cell wall.

The cold plasma technique, developed especially in recent years, opens the door to new materials with unique properties. This is related both to the plasma deposited thin films, which constitute integrally new materials, and to the plasma surface treatments, which drastically change the surface properties of conventional materials. Looking for novel solutions for innovative energy systems, it has been found that the both types of plasma activity are very useful for this purpose. The objective of this paper is to demonstrate the possibilities of the cold plasma technique for preparation of new materials for energy systems. A few examples of recent studies on such materials are presented. A special attention is focused on plasma deposited optoelectronically active thin films for solar cells, nanocatalytic thin films for fuel cells and plasma treated carbon electrodes for supercapacitors. These examples confirm the important role of the cold plasma technique in the development of modern and advanced energy systems.

This paper presents an analysis of the properties of sintered steels in terms of their practical use for production of interconnectors in fuel cells. The study covers measurements of mechanical properties, microstructural examinations and analysis of surface profile in the sintered samples. The porosity and contact resistance between interconnectors and gas diffusion layer are also examined. The main criterion adopted for choosing a particular material for the components in fuel cells is their corrosion resistance under operating conditions of hydrogen fuel cells. In order to determine resistance to corrosion in the environment of operation of fuel cells, potentiokinetic curves are registered for synthetic solution 0.1 M H₂SO₄ + 2 ppmF^- at 80°C.

Porous, graded ceramic structures are of high relevance in the field of energy conversion as well as in catalysis, and additionally in filtration technology and in biomedical applications. Among different technologies for the tailored design for such structures we demonstrate here a new environmental friendly UV curing-based concept to prepare laminated structures with pore sizes ranging from a few microns up to 50 microns in diameter and with porosities ranging from 10% up to 75 vol.% porosity.

In order to move towards a sustainable existence in our critically energy dependent society there is a continuing need to adopt environmentally sustainable methods for energy production, storage and conversion. A fuel cell is an energy conversion device that generates electricity and heat by electrochemically combining a gaseous fuel and an oxidant gas through electrodes and across an ion conducting electrolyte. The use of fuel cells in both stationary and mobile power applications can offer significant advantages for the sustainable conversion of energy. Currently the cost of fuel cell systems is greater than that of similar, already available products, mainly because of small scale production and the lack of economies of scale. The best fuel for fuel cells is hydrogen and another barrier is fuel flexibility. Benefits arising from the use of fuel cells include efficiency and reliability, as well as economy, unique operating characteristics and planning flexibility and future development potential. By integrating the application of fuel cells, in series with renewable energy storage and production methods, sustainable energy requirements may be realized. As fuel cell application increases and improved fuel storage methods and handlings are developed, it is expected that the costs associated with fuel cell systems will fall dramatically in the future.

Compared to hydrogen, ethanol and methanol have the advantages in storage and transportation. Catalysts are the key for developing direct alcohol fuel cells (DAFCs) with highly efficient performance. For ethanol oxidation, breaking the C–C bond is a crucial factor for its complete oxidation at lower overpotentials and increase of cell performance. Due to the CO intermediates generated during the reaction, the bifunctional mechanism is particularly important for methanol oxidation. This chapter reviews the rational design, reactivity stability, and mechanistic investigation of high-efficiency nanocatalysts over the past decades. It is worth noting that widespread commercialization of DAFCs still face many barriers, such as high cost and low stability. In addition, this chapter describes the application of powerful analytical techniques (such as ¹H nuclear magnetic resonance (NMR) spectroscopy, on-line differential electrochemical mass spectrometry (DEMS), and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy) in the oxidation reactions of methanol and ethanol, which are helpful for our in-depth understanding of the reaction process as well as the promoted commercialization of DAFCs.

Supercapacitors and fuel cells are essential energy devices for the implementation of a real renewable energy economy. The development of highly efficient and low-cost electrode materials is one of the major challenges to improve these devices. Biomass-derived carbon materials are postulated as a very interesting alternative, as they can be obtained from inexpensive precursors and abundant resources obtained directly from nature. However, they commonly exhibit an underdeveloped porous structure and a lack of controlled surface functionalities that limit their real application. Therefore, it is essential to apply different approaches to modify and design their properties to fit the requirements of energy storage and conversion devices. This chapter attempts to provide a broad overview of the most promising strategies that can be followed to design biomass-derived carbon materials with highly efficient performance in energy applications, such as supercapacitors and fuel cells.