12 research outputs found
Evaluation of Reduced-Graphene-Oxide Aligned with WO3-Nanorods as Support for Pt Nanoparticles during Oxygen Electroreduction in Acid Medium
Hybrid supports composed of chemically-reduced graphene-oxide-aligned with
tungsten oxide nanowires are considered here as active carriers for dispersed
platinum with an ultimate goal of producing improved catalysts for
electroreduction of oxygen in acid medium. Here WO3 nanostructures are expected
to be attached mainly to the edges of graphene thus making the hybrid structure
not only highly porous but also capable of preventing graphene stacking and
creating numerous sites for the deposition of Pt nanoparticles. Comparison has
been made to the analogous systems utilizing neither reduced graphene oxide nor
tungsten oxide component. By over-coating the reduced-graphene-oxide support
with WO3 nanorods, the electrocatalytic activity of the system toward the
reduction of oxygen in acid medium has been enhanced even at the low Pt loading
of 30 microg cm-2. The RRDE data are consistent with decreased formation of
hydrogen peroxide in the presence of WO3. Among important issues are such
features of the oxide as porosity, large population of hydroxyl groups, high
Broensted acidity, as well as fast electron transfers coupled to unimpeded
proton displacements. The conclusions are supported with mechanistic and
kinetic studies involving double-potential-step chronocoulometry as an
alternative diagnostic tool to rotating ring-disk voltammetry.Comment: arXiv admin note: text overlap with arXiv:1805.0315
Solar chargers based on new dye-based photovoltaic modules and new supercapacitors
Electricity storage is one of the best-known methods of balancing the energy supply and demand at a given moment. The article presents an innovative solution for the construction of an electric energy storage device obtained from an innovative photovoltaic panel made of new dye-based photovoltaic modules and newly developed supercapacitors – which can be used as an emergency power source. In the paper, for the first time, we focused on the successful paring of new dye-sensitized solar cell (DSSC) with novel supercapacitors. In the first step, a microprocessor stand was constructed using Artificial Intelligence algorithms to control the parameters of the environment, as well as the solar charger composed of six DSSC cells with the dimensions of 100_100 mm and 126 CR2032 coin cells with a total capacitance of 60 F containing redox-active aqueous electrolyte. It was proven that the solar charger store enough energy to power, i.e. SOS transmitter or igniters, using a 5 V signal
Water/N,N-Dimethylacetamide-Based Hybrid Electrolyte and Its Application to Enhanced Voltage Electrochemical Capacitors
The growing interest in hybrid (aqueous–organic) electrolytes for electrochemical energy storage is due to their wide stability window, improved safety, and ease of assembly that does not require a moisture-free atmosphere. When it comes to applications in electrochemical capacitors, hybrid electrolytes are expected to fill the gap between high-voltage organic systems and their high discharge rate aqueous counterparts. This article discusses the potential applicability of aqueous–organic electrolytes utilizing water/N,N-dimethylacetamide (DMAc) solvent mixture, and sodium perchlorate as a source of charge carriers. The hydrogen bond formation between H2O and DMAc (mole fraction xDMAc = 0.16) is shown to regulate the original water and cation solvation structure, thus reducing the electrochemical activity of the primary aqueous solution both in the hydrogen (HER) and oxygen (OER) evolution reactions region. As a result, an electrochemical stability window of 3.0 V can be achieved on titanium electrodes while providing reasonable ionic conductivity of 39 mS cm−1 along with the electrolyte’s flame retardant and anti-freezing properties. Based on the diagnostic electrochemical studies, the operation conditions for carbon/carbon capacitors have been carefully optimized to adjust the potential ranges of the individual electrodes to the electrochemical stability region. The system with the appropriate electrode mass ratio (m+/m− = 1.51) was characterized by a wide operating voltage of 2.0 V, gravimetric energy of 13.2 Wh kg−1, and practically a 100% capacitance retention after 10,000 charge–discharge cycles. This translates to a significant rise in the maximum energy of 76% when compared to the aqueous counterpart. Additionally, reasonable charge–discharge rates and anti-freeze properties of the developed electrolyte enable application in a broad temperature range down to −20 °C, which is demonstrated as well
Electrocatalytic properties of manganese and cobalt polyporphine films toward oxygen reduction reaction
International audienceNovel member of polymetalloporphines, namely manganese polymetalloporphine of type I (pMnP-I) obtained by ion exchange from magnesium polyporphine of type I (pMgP-I) is reported for the first time and compared to its cobalt analogue (pCoP-I). Both polymer films have been obtained via two-step procedure: demetaladon of the pMgP-I electrode film via its exposure to trifluoroacetic acid solution, resulting in formation of the metal-free polyporphine of type I (pH(2)P-I) followed by electrochemically induced incorporation of Co or Mn ions from the acetonitrile solution of cobalt and manganese perchlorates. A further oxidative transformation of pCoP-I, polymer films has led to the corresponding polyporphines of type II, pCoP-II and pMnP-II, possessing such unique features as condensed polymer structure with a very high density of active sites and high electronic conductivity within a very broad potential range including the one corresponding to the neutral (uncharged) state of the polymer matrix. Both polymers of type II also exhibit interesting electrocatalytic activity toward oxygen electroreduction in aqueous neutral (pH 6.7) and alkaline (pH 13) media which was evaluated under cyclic voltammetric and steady-state conditions. The results demonstrate that the efficiency (regardless of the electrolyte) of both polymetalloporphines is comparable to bare platinum electrode. The effect of annealing of polymer-modified electrodes on their catalytic properties has also been considered
Inorganic–organic modular silicon and dye-sensitized solar cells and predicted role of artificial intelligence towards efficient and stable solar chargers based on supercapacitors
Abstract Appropriate and rational management of the energy produced by renewable energy sources is one of the most urgent challenges for the global energy sector. This paper is devoted to the systematic experimental and theoretical studies of a modular solar charger based on silicon and dye-sensitized solar cells as an energy source, and supercapacitor as an energy bank. Using the MathCAD program, I–V characteristics were plotted for both a single cell and a photovoltaic module based on various series-to-parallel connections. To assess the surface quality of the modules, additional tests using a thermal imaging camera were carried out as well. The charging characteristics of the supercapacitor (two series-connected cells with a capacity of 300 F), were determined depending on the parameters of the photovoltaic module as well as considering the influence of the voltage balancing system and control system. The charge, discharge, and recharge characteristics were carefully analyzed to optimize the operating conditions, i.e. the number of photovoltaic cells. To evaluate the stability of parameters with operation time, and their temperature dependence (17–65 °C), solar modules were tested for ten days under Central European weather conditions. Importantly, a comparative analysis of solar chargers based on different configurations of photovoltaic cells showed an increase in electrical parameters for the proposed modular inorganic–organic concept compared to dye-sensitized solar cells produced alone on a rigid substrate. Finally, preliminary assumptions (requirements) were developed regarding the electrical and optical parameters for new dye-sensitized solar cells that could be used in the innovative solar charger instead of silicon cells along with a predicted role of artificial intelligence (AI) in these devices
Integration of solid-state dye-sensitized solar cell with metal oxide charge storage material into photoelectrochemical capacitor
A solid-state photo-rechargeable capacitor (photocapacitor) is obtained here by coupling a dye-sensitized solar cell and a ruthenium oxide based electrochem. capacitor. This integrated system permits direct storage of energy generated by sunlight within a single optoelectronic microelectrochem. device. It utilizes three planar electrodes arranged sequentially to include a polymer hole conductor (poly-(3-hexylthiophene-2,5-diyl)), between the titanium oxide photoanode modified with dye (E)-3-(5-(4-(Bis(20,40-dibutoxybiphenyl-4-yl)amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid (D35) and the intermediate silver electrode as well as two hydrous ruthenium oxide layers (sepd. by protonically conducting Nafion membrane) between the intermediate (silver) and the external (counter) electrode. Upon integration of the capacitor and dye-sensitized solar cell into a single photocapacitor hybrid device, the following parameters were obtained under simulated 100 mW cm-2 solar illumination: specific capacitance, 407 F g-1 (3.26 F cm-2); energy and power densities, 0.17 mWh cm-2 and 0.34 mW cm-2 and coulombic efficiency, 88%. These data together with results of expts. performed at different light intensities (10-100 mW cm-2) are consistent with very good performance of the optoelectronic device under various light conditions
Non-Precious Metal Electrocatalysts for the Oxygen Reduction Reaction Based on Nitrogen Doped Graphene: Catalysts Development and Electrode Structure Design
(ORAL) The design of new functional nanomaterials for developing new electrocatalysts for oxygen reduction reaction (ORR) in acid and alkaline media. The research has been focused on developing carbon nanostructures especially graphene/graphene oxide materials with superior structural and functional properties for fuel cell applications. Electrocatalysts based on graphene and graphene-oxide (GO) are more homogeneous and possess properties such as excellent conductivity, good chemical stability and can be functionalized in a controlled manner. To facilitate fabrication, immobilization and distribution of non-precious metal nanoparticles, various types of graphene (e.g. reduced graphene oxide, RGO, and CFx graphene with carbon black) have been modified with the different transition metals (e.g. Co, Ni, Ag, Au, Cu, Mn) analogue of polynuclear Prussian Blue, namely
with ultra-thin Co, and Ni hexacyanoferrate layers. Following the heat-treatment step at higher temperatures, some thermal decomposition of the cyanometallate network occurs and, consequently, metallic sites are generated. Their formation and distribution are facilitated by the voltammetric potential cycling in KOH electrolyte. The most promising electrocatalytic results with respect to the reduction of oxygen (the highest currents and the most positive electroreduction potentials) have been obtained when graphene nanostructures are combined or intermixed with Vulcan XC-72R nanoparticles. What is even more important that, due to the presence of the polynuclear cyanoferrate modifier or linker, the amounts of the undesirable hydrogen peroxide intermediate are significantly decreased. An electrocatalytic system, that utilizes metal hexacyanometallates nanoparticles modified graphene and graphene related materials, is developed and characterized here using transmission electron microscopy and such electrochemical diagnostic techniques as cyclic volammetry and rotating ring-disk voltammetry in a 0.5 M H2SO4 electrolyte and in a 0.1 M KOH electrolyte and upon introduction (as cathode) to the low-temperature hydrogen-oxygen fuel cell. Comparative measurements have been performed against the model noble metal (Vulcan-supported
platinum nanoparticles) catalyst
Iodide Electrolyte-Based Hybrid Supercapacitor for Compact Photo-Rechargeable Energy Storage System Utilising Silicon Solar Cells
The one of the most important issues in constructing light-harvesting photovoltaic (PV) systems with a charge storage element is its reliable and uninterrupted use in highly variable and weather-dependent conditions in everyday applications. Herein, we report the construction and applicability evaluation of a ready-to-use portable solar charger comprising a silicon solar cell and an enhanced energy hybrid supercapacitor using activated carbon electrodes and iodide-based aqueous electrolyte to stabilise the PV power under fluctuating light conditions. The optimised electrode/electrolyte combination of a supercapacitor was used for the construction of a 60 F/3 V module by a proper adjustment of the series and parallel connections between the CR2032 coin cells. The final photo-rechargeable device was tested as a potential supporting system for pulse electronic applications under various laboratory conditions (temperature of 15 and 25 °C, solar irradiation of 600 and 1000 W m−2)
Evaluation of Reduced-Graphene-Oxide Aligned with WO3-Nanorods as Support for Pt Nanoparticles during Oxygen Electroreduction in Acid Medium
ybrid supports composed of chemically-reduced graphene-oxide-aligned with tungsten oxide nanowires are considered here as active carriers for dispersed platinum with an ultimate goal of producing improved catalysts for electroreduction of oxygen in acid medium. Here WO3 nanostructures are expected to be attached mainly to the edges of graphene thus making the hybrid structure not only highly porous but also capable of preventing graphene stacking and creating numerous sites for the deposition of Pt nanoparticles. Comparison has been made to the analogous systems utilizing neither reduced graphene oxide nor tungsten oxide component. By over-coating the reduced-graphene-oxide support with WO3 nanorods, the electrocatalytic activity of the system toward the reduction of oxygen in acid medium has been enhanced even at the low Pt loading of 30 microg cm-2. The RRDE data are consistent with decreased formation of hydrogen peroxide in the presence of WO3. Among important issues are such features of the oxide as porosity, large population of hydroxyl groups, high Broensted acidity, as well as fast electron transfers coupled to unimpeded proton displacements. The conclusions are supported with mechanistic and kinetic studies involving double-potential-step chronocoulometry as an alternative diagnostic tool to rotating ring-disk voltammetry
Toward Pt-Free Anion-Exchange Membrane Fuel Cells: Fe–Sn Carbon Nitride–Graphene Core–Shell Electrocatalysts for the Oxygen Reduction Reaction
We report on the
development of two new <i>Pt-free</i> electrocatalysts (ECs)
for the oxygen reduction reaction (ORR) process
based on graphene nanoplatelets (GNPs). We designed the ECs with a <i>core–shell</i> morphology, where a GNP <i>core</i> support is covered by a carbon nitride (CN) <i>shell.</i> The proposed ECs present ORR active sites that are not associated
with nanoparticles of metal/alloy/oxide but are instead based on Fe
and Sn subnanometric clusters bound in <i>coordination nests</i> formed by carbon and nitrogen ligands of the CN <i>shell</i>. The performance and reaction mechanism of the ECs in the ORR are
evaluated in an alkaline medium by cyclic voltammetry with the thin-film
rotating ring-disk approach and confirmed by measurements on gas-diffusion
electrodes. The proposed GNP-supported ECs present an ORR overpotential
of only ca. 70 mV higher with respect to a conventional Pt/C reference
EC including a XC-72R carbon black support. These results make the
reported ECs very promising for application in anion-exchange membrane
fuel cells. Moreover, our methodology provides an example of a general
synthesis protocol for the development of new <i>Pt-free</i> ECs for the ORR having ample room for further performance improvement
beyond the state of the art