Technical feasibility of a proton battery with an activated carbon electrode

The technical feasibility of a small-scale ‘proton battery’ with a carbon-based electrode is demonstrated for the first time. The proton battery is one among many potential contributors towards meeting the gargantuan demand for electrical energy storage that will arise with the global shift to zero greenhouse emission, but inherently variable, renewable energy sources. Essentially a proton battery is a reversible PEM fuel cell with an integrated solid-state electrode for storing hydrogen in atomic form, rather than as molecular gaseous hydrogen in an external cylinder. It is thus a hybrid between a hydrogen-fuel-cell and battery-based system, combining advantages of both system types. In principle a proton battery can have a roundtrip energy efficiency comparable to a lithium ion battery. The experimental results reported here show that a small proton battery (active area 5.5 cm²) with a porous activated carbon electrode made from phenolic resin and 10 wt% PTFE binder was able to store in electrolysis (charge) mode very nearly 1 wt% hydrogen, and release on discharge 0.8 wt% in fuel cell (electricity supply) mode. A significant design innovation is the use of a small volume of liquid acid within the porous electrode to conduct protons (as hydronium) to and from the nafion membrane of the reversible cell. Hydrogen gas evolution during charging of the activated carbon electrode was found to be very low until a voltage of around 1.8 V was reached. Future work is being directed towards increasing current densities during charging and discharging, multiple cycle testing, and gaining an improved understanding of the reactions between hydronium and carbon surfaces.     

Comparison of different electrodes in hydrogen gas production from electrohydrolysis of wastewater organics using photovoltaic cells (PVC)

Electrical power generated by a photovoltaic cell (PVC) was supplied to diluted industrial wastewater in a mechanically mixed and sealed stainless-steel reactor for hydrogen gas production. Three different electrodes, graphite, stainless steel and aluminum rods were used for comparison. Protons released from decomposition of organic compounds and electrons provided by the DC current reacted to form hydrogen gas. The highest cumulative hydrogen gas formation (CHF) was obtained with the aluminum electrode (120 L in 8 days) and the lowest was with the graphite electrode (4 L). Hydrogen gas production from wastewater was 2.4 times higher than that produced from water when aluminum electrodes were used. TOC content of wastewater was reduced from 2400 to 1700 mg L⁻¹ with nearly 29% TOC removal within 6 days. CHF from wastewater was 76 L within 18 days with the stainless-steel electrodes while CHF from water was only 9.5 L. Fermentative hydrogen gas production from wastewater was negligible in the absence PVC. Energy conversion efficiency for hydrogen gas production (hydrogen energy/electric energy) was found to be 74% with the aluminum electrodes.     

Integrated approach for textile industry wastewater for efficient hydrogen production and treatment through solar PV electrolysis

Combining solar PV based electrolysis process and textile dyeing industry wastewater for hydrogen production is considered feasible route for resource utilization. An updated experimental method, which integrates resource availability to assess the wastewater based hydrogen production with highlights of wastewater treatment, use of solar energy to reduce the high-grade electricity for electrolysis (voltage, electrode materials) efficiency of the process was employed. Results showed that maximum pollutant removal efficiency in terms of conductivity, total dissolved solids, total suspended solids, biological oxygen demand, chemical oxygen demand, hardness, total nitrogen and total phosphorus were obtained from ≅73% to ≅96% at 12 V with steel electrode for pollutant load. The maximum input voltage was found at 3 V for the best efficiency i.e. 49.6%, 67.8% and 57.1% with carbon, steel and platinum electrodes respectively. It was observed that with high voltage (12 V) of the electrolyte the rate of production of hydrogen was higher with carbon, steel and platinum electrodes. However, the increase in the efficiency of the production of hydrogen was not significant with high voltage, may be due to energy loss through heat during extra-over potential voltage to the electrodes. Hence, this integrated way provides a new insight for wastewater treatment and hydrogen energy production simultaneously.     

Electrocatalytic oxidation of hydrogen peroxide on the surface of nano zeolite modified carbon paste electrode

This study investigated the use of synthesized nanozeolite Y to prepare modified carbon paste electrode for electrocatalytic oxidation of hydrogen peroxide. In order to prepare the modified electrodes, the nickel ions were doped to Y zeolite framework through ion exchange mechanism and the electrochemical behaviour of the proposed modified electrode was studied using the cyclic voltammetry technique. The obtained results revealed that modified carbon paste electrode in the form of Ni/NiYCPE is the best electrode for the oxidation of hydrogen peroxide in the alkaline media. The hydrogen peroxide transfer coefficient (α) and the current density were calculated as 0.54 and 6.7 mA/cm², respectively. The catalytic rate constant (K) for this electrocatalytic reaction was calculated through the chronoamperometric technique (K = 0.43 × 10⁴ cm²s^?1mol^?1).     

Effects of porous support microstructure enabled by the carbon microsphere pore former on the performance of proton-conducting reversible solid oxide cells

Proton-conducting reversible solid oxide cells (PC-RSOCs) have attracted extensive attention due to their high efficiencies as energy conversion devices. Generally, the performance of the cell is affected to a certain extent by the microstructure of the electrodes, which is closely related to the gas diffusion and surface reaction processes. Herein, different contents of the carbon microspheres (CMSs) are used as the pore formers to control the microstructure of the hydrogen electrode. Experimental results reveal that the porosity, line shrinkage, and thermal expansion coefficient of the hydrogen electrode support simultaneously increase with the CMS content. The support with 30 wt% CMS presents high porosity (39.27 vol%) with uniform-size pores. Subsequently, the corresponding single cells were fabricated successfully, particularly, the cell with 30 wt% CMS exhibiting the best electrochemical performance in both fuel cell (0.46 W cm^?2 at 700 °C) and electrolysis cell (1.41 A cm^?2 at 1.3 V and 700 °C) operational modes. Further results demonstrated the highest performance was attributed primarily to the maximal three-phase boundary length, which mainly originates from the high porosity and unique microstructure of the hydrogen electrode.     

Cathodic hydrogen recovery and methane conversion using Pt coating 3D nickel foam instead of Pt-carbon cloth in microbial electrolysis cells

A cheap but efficient electrode material is required to explore and apply to microbial electrolysis cell (MEC) with high hydrogen evolution reaction (HER) efficiency and low over-potential loss. Pt coating carbon cloth (Pt/CC) was one of the most efficient catalyst for hydrogen production in current lab research, but it is difficult to be applied in practice because of expensive cost and week strength from the base material (carbon cloth). Thus a cheap and effective supporting base material is worth to evaluate on hydrogen recovery and loss to methane for the MEC future application. In this study, nickel foam (NF) was used as an alternative to expensive carbon cloth, and NF coated with Pt (Pt/NF) was applied and evaluated through catalytic performance, hydrogen production efficiency and economic assessment in comparison with Pt/CC. The Pt/NF showed a competitive HER performance to Pt/CC. The highest hydrogen yield was reached 0.71 ± 0.03 m³/m³·d by Pt/NF under 0.8 V, which exceeded 6%, 10% over Pt/CC and NF, respectively. The energy efficiency relative to the electrical energy input was 127% for Pt/NF and 123%, 110% for Pt/CC and NF, respectively. For fifteen cycles, the methane content of Pt/NF got the lowest due to its higher hydrogen evolution activity. The economic analysis showed a 56% reduction when using Pt/NF as supporting base in place of carbon cloth to achieve similar performance. The linear sweep voltammetry (LSV) showed the possibility to further reduce input voltage in a long term operation.     

Vertically aligned carbon nanotube – Polyaniline nanocomposite supercapacitor electrodes

We develop a fast and cost effective method for the fabrication of a nanocomposite supercapacitor electrode. In this study aluminum foils were decorated with vertically aligned carbon nanotubes (VACNT) via chemical vapor deposition (CVD) method, which was followed by the electrodeposition of polyaniline (PANI) layer on top of the VACNTs. Electrochemical behavior of the fabricated nanocomposite electrodes were evaluated through cyclic voltammetry, galvanostatic charge discharge cycles and electrochemical impedance spectroscopy method. Fabricated VACNT/PANI nanocomposite electrodes through 15 electrodeposition cycles showed significant electrochemical performance. The specific capacity of these electrodes was calculated as 16.17 mF/cm² at a current density of 0.25 mA/cm².     

Fabrication of Mo-modified carbon felt as candidate substrate for electrolysis: Optimization of pH,current and metal amount

Mo was electrochemically deposited over a carbon felt (C) support in order to enhance hydrogen evolution activity of the support and make it a candidate for further modifications. For this aim, the effects of pH of deposition bath solution, deposition current and amount of deposited Mo were studied and optimized. Hydrogen evolution activity of the electrodes was evaluated in 1 M KOH solution with the help of electrochemical techniques. Surface structures of the electrodes were examined by scanning electron microscopy (SEM). It was found that 1 g Mo/g C modified electrode at pH 6 and 50 mA current exhibits the best hydrogen releasing performance. The enhanced current density at this electrode under ?1.60 V(Ag/AgCl) was 59.6% with respect to the bare support, which demonstrates that modifying the support by a thin Mo layer favors the hydrogen evolution reaction (HER) and reduces the energy requirement. The high hydrogen evolution performance of this modified substrate was assigned to its excellent structure, large surface area as well as high intrinsic catalytic activity of Mo. According to experimental findings, the Mo-modified C substrate was suggested for preparation of further modified electrode materials, especially with trace amounts of precious metals.     

Optimization on the electrochemical properties of La2NiO4+δ cathodes by tuning the cathode thickness

The electrochemical properties of La₂NiO_4+δ electrodes were investigated as a function of the electrode thickness based on three-electrode half cells. The electrocatalytic activity of the electrodes with the varied thicknesses ranging from 5 to 30 μm was surveyed by electrochemical impedance spectroscopy technique under open-current voltage conditions. The cathodic polarization curves of these electrodes were also inspected. The results indicated that the electrochemical properties of these electrodes were highly dependent on their thickness. The polarizations of involved electrode reaction processes displayed different variations with changing the electrode thickness. Tuning the electrode thickness was confirmed to be effective for optimizing the electrochemical properties. Among the investigated electrodes, the electrode with a thickness of ～20 μm achieved the optimal properties. At 800 °C in air, this electrode exhibited a polarization resistance of 0.24 Ω cm², an exchange current density of 201 mA cm^?2 and an overpotential of 40 mV at 200 mA cm^?2. On this ground, an anode-supported single cell with ～20 μm thick La₂NiO_4+δ cathode was fabricated. At 800 °C and using hydrogen fuel, this single cell attained a maximum powder density of 500 mW cm^?2.     

Water from the Vistula Lagoon as a medium in mixotrophic growth and hydrogen production by Platymonas subcordiformis

Platymonas subcordiformis is a marine microalgae that under favorable environmental conditions change metabolism pathways to hydrogen production in direct biophotolysis. Effective hydrogen production by Platymonas subcordiformis depends on application of efficient and economically viable biomass production technologies. In the study, the natural water from Vistula Lagoon was used for microalgae cultivation. No statistically significant differences were found regarding the biomass production in the natural water and synthetic medium. The influence of mixotrophic conditions on growth rate and biomass production of Platymonas subcordiformis was also examined. The highest biogas production of 138.45 ± 3.39 mL with the rate of 1.15 ± 0.03 mL/h was noted by the biomass cultivated on synthetic medium with glucose supplementation. Similarly high biogas production was observed by the biomass cultivated on natural water with glucose addition (1.11 ± 0.14 mL/h). The use of the waters from Vistula Lagoon resulted in high yields of hydrogen production, which might reduce costs of biofuel production.     

Experimental investigation of solar assisted hydrogen production from water and aluminum

Sustainable production of hydrogen at high capacities and low costs is one the main challenges of hydrogen as a future alternative fuel. In this paper, a new hydrogen production system is designed and fabricated to investigate hydrogen production using aluminum and solar energy. Numerous experiments are performed to evaluate the hydrogen production rate, quantitatively and qualitatively. Moreover, correlations between the total hydrogen production volume over time and other parameters are developed and the energy efficiency and conversion ratio of the system are determined. Also, a method is developed to obtain an optimal and stable hydrogen production rate based on system scale and consumed materials. It is observed that at low temperatures, the hydrogen production volume, efficiency and COP of the system increase at a higher sodium hydroxide molarity. In contrast, at high temperatures the results are vice versa. The maximum hydrogen production volume, hydrogen production rate, reactor COP and system efficiency using 0.5 M NaOH solution containing 3.33 g lit^?1 aluminum at 30 °C are 6119 mL, 420 mL min^?1, 1261 mL H₂ per 1 g of Al, and 16%, respectively.     

High-performance ceramic composite electrodes for electrochemical hydrogen pump using protonic ceramics

Ceramic composite electrodes comprising an electron-conducting ceramic (Sr-doped LaVO₃), a protonic ceramic [Cu and Y-doped Ba(Ce,Zr)O₃], and small amounts of CeO₂ and Pd as catalysts were fabricated using an infiltration method for use in an electrochemical hydrogen pump and the hydrogen fluxes and the faradaic efficiency were measured by analyzing the gas compositions. This composite electrode performed well; the area-specific resistance of the electrode polarization at 1 A cm^?2 was just 0.15 Ω cm² at 973 K in hydrogen pumping mode, and the overpotential at a large current density of 2 A cm^?2 was only about 1.1 V at 973 K. To optimize the operating conditions, the effects of the steam vapor pressure and hydrogen partial pressure on the electrochemical performance of the hydrogen pump were investigated. The steam in the sweep side was consumed by the steam electrolysis due to the partial oxygen conductivity. Therefore, supplying insufficient steam to the cathode was found to cause a steep increase in the voltage at high currents owing to a decrease in the proton conductivity.     

Investigation of alkaline water electrolysis performance for different cost effective electrodes under magnetic field

Alkaline water electrolysis is the easiest methods for hydrogen production because of their simplicity. Although the simplicity is an advantage; reducing the energy consumption and maintaining the durability and the safety of these systems are the main challenges. In this paper, alkaline water electrolysis system, that uses cost effective electrode materials and magnetic field effects are presented. Cost effective electrodes such as high carbon steel, 304 stainless steel, 316L low carbon steel and graphite material are used for the hydrogen production. After the selection of the best electrode pair, effects of magnetic field to hydrogen production and change of current density are investigated for KOH electrolytes in different concentrations (5 wt%, 10 wt% and 15 wt%). According to the experimental observations the direction of the Lorentz Force affects the hydrogen production and current density. When the Lorentz Force is directed upward, it enhances the hydrogen production for 5 wt% and 15 wt% KOH solution by almost 17%. The increase in current density for 5 wt%, 10 wt% and 15 wt% concentration is 19%, 5%, 13%, respectively. Forced convection in the magnetic field enhances the separation of gas bubbles from electrode surface. Downward directed Lorentz Force decreases hydrogen production and current density values significantly. For 5 wt%, 10 wt% and 15 wt% the hydrogen production decreases by 14%, 8%, 7%, respectively. Similarly, current density for downward directed Lorentz Force decreases by 11%, 7%, 4%, respectively.     

Pt/Fe-NF electrode with high double-layer capacitance for efficient hydrogen evolution reaction in alkaline media

The electrode with high catalytic activity, low hydrogen overpotential and low cost is desired for hydrogen evolution reaction (HER) via electrocatalytic water splitting. In this study, Pt/Fe-Ni foam (Pt/Fe-NF) electrode was synthesized via cathodic electrodeposition followed by impregnation deposition. Physical and electrochemical properties of Pt/Fe-NF, NF and Pt/NF electrodes were characterized by various techniques. The Pt/Fe-NF electrode exhibited better electrochemical activity for HER under alkaline condition than those of Pt/NF and NF electrodes, owing to the introduction of zero valences Pt and Fe onto the NF, and synergetic effect resulted from the formation of Fe-Ni alloy. Furthermore, Pt/Fe-NF electrode showed extremely high double-layer capacitance (69.1 mFcm^?2), suggesting high active sites for the Pt/Fe-NF. Tafel slope of Pt/Fe-NF was 59.9 mV dec^?1, indicating that the Volmer-Heyrovsky HER mechanism was the rate-limiting step. The Pt/Fe-NF electrode with great electrocatalytic activity is a promising electro-catalyst for industrial hydrogen production from alkaline electrolyte.     

Wire-arc sprayed nickel based coating for hydrogen evolution reaction in alkaline solutions

Nickel based coatings of various Ni/Al ratios were prepared by the wire-arc spray technique on mild steel substrate. High porosity Ni based electrodes were obtained by leaching out the aluminum in concentrated KOH at 70°C. These electrodes were studied under hydrogen evolution reaction in 1 M NaOH at 25°C. Good mechanical electrode stability and very low overvoltage values, i.e., down to 179 mV at 0.25 A/cm², were observed. These low overvoltages have been related to the porosity of the material by AC impedance measurements. This spray technique exhibits several advantages for processing large scale electrode materials at low cost.     

Investigation on energy storage and conversion properties of multifunctional PANI-MWCNT composite

Polyaniline-multiwalled carbon nanotube (PANI-MWCNT) composite synthesized through chemical polymerization is investigated as a possible electrode material for supercapacitor as well as an electro-catalyst for hydrogen evolution reaction (HER) in acidic medium. UV–Vis spectroscopy, FTIR spectroscopy and field emission scanning electron microscopy (FESEM) have been used to characterize the electrode material. The binder-free electrodes were prepared and they exhibit a specific capacitance of 540.29 F g^?1 at a scan rate of 2 mV s^?1 in 1 M H₂SO₄ electrolyte. The material exhibits excellent pseudocapacitive behaviour due to the presence of PANI with long-term cyclic stability of 87.4% retention after 5000 cycles. PANI-MWCNT composite also shows good HER activity, with overpotential of ?395 mV.     

Surface characteristics and electrolysis efficiency of a Palladium-Nickel electrode

In view to finding a better electrode for water electrolysis-the hydrogen and oxygen evolution efficiencies of a Pd-80 at% Ni electrode along with its surface oxidation-reduction characteristics were investigated in alkaline medium using cyclic voltammetry. On cycling the electrode in between the potential range of ?1.0 to +0.65 V, two oxidation and two reduction transformations were observed. The origins of the transformations were found out. Most of the transformation peak potentials were found to be different than that of Pd and Ni electrodes. The generation of (PdNi)(III) species over the electrode surface identified to be the crucial for the oxygen evolution and continuous cycling up to 100 min succeeded to obtain its saturated layer. Tafel plots for both the hydrogen and oxygen evolution reactions (HER and OER) showed two regions. The kinetic parameters for the HER and OER, i.e., exchange current density at zero overpotential (i_o) and slope (b) values for both the low and high overpotential (η) regions were found out. For the HER, the i_o and b values are found to be 6.17 × 10^?2 and 4.36 mA/cm² and 137.0 and 343.9 mV/dec, respectively. For the OER, the values are 2.83 × 10^?3 and 2.35 mA/cm² and 72.8 and 215.1 mV/dec, respectively. On comparing these kinetic values with that available for Pd, Ni and Pd-50 at% Ni, it is realized that the investigated Pd-80 at% Ni electrode showed better electrolysis efficiencies than that of its component materials and Pd-50 at% Ni electrode.     

Proposal for a new system for simultaneous production of hydrogen and hydrogen peroxide by water electrolysis

Authors have proposed a new hydrogen production system that simultaneously produces hydrogen and hydrogen peroxide by water electrolysis. Experimental apparatus of the system is composed of a hydrogen electrode with platinum meshes, a hydrogen peroxide electrode with carbon material and an electrolyte with Nafion^®. In this paper, the superiority of the system is outlined, and the experimental results of the electrolytic synthesis of hydrogen and hydrogen peroxide from water are reported. Hydrogen peroxide is synthesized at the high efficiency when some kinds of carbon material are used as the hydrogen peroxide electrode. Furthermore, the possibility of applying the solar energy to this system is also discussed.     

Electrooxidation of formaldehyde as a fuel for fuel cells using Fe2+-nano-zeolite modified carbon paste electrode

This study aimed to investigate the application of nano ZSM-5 zeolite for preparation of modified carbone paste electrode for electrocatalytic oxidation of formaldehyde. The electrochemical behavior of modified carbon paste electrodes in the forms of Fe/FeZSM-5CPE and unmodified carbon paste electrode were studied using cyclic voltammetric and chronoamprometric techniques. The obtained results show that the modified carbon paste electrode (Fe/FeZSM-5CPE) is the suitable electrode for electrooxidation of formaldehyde in the acidic solution. The transfer coefficient and current density for formaldehyde were calculated 0.23 and 19.8 mA/cm², respectively. The rate constant for catalytic reaction was calculated as 3.6 × 10³ cm³ s^?1 mol^?1 via Cottrell equation.     

Biodegradation of Potamogeton pectinatus biomass by hydrogen and methane coproduction: Effect of different pretreatments and parallel factor analysis

To enhance the hydrogen and methane coproduction potential, three pretreatments (i.e., acid, alkali and cellulase) were investigated during a two-stage anaerobic fermentation using Potamogeton pectinatus biomass. The fluorescence spectral characteristics of the dissolved organic matter (DOM) from the two-stage effluents, coupled with parallel factor analysis, were studied. The maximum hydrogen proportions (42.65%) and production rate (4.1 mL h^?1) were obtained under the 0.5 mol L^?1 HCl pretreatment. The highest methane proportions (52.82%) and production rate (14.2 mL h^?1) were observed under the 0.5 mol L^?1 HCl and 10 mg g^?1 cellulase pretreatments, respectively. Combined with fluorescence spectra and parallel factor analysis, three fluorescent components were identified, and the protein-like substances were determined to be dominant. Using the acid pretreatment, the change of the maximum fluorescence intensities in the DOM was the most significant among the three pretreatments, followed by that of the cellulose pretreatment. The result indicated that the macromolecular substances in P. pectinatus can be decomposed by effective pretreatment and thereby enhances the hydrogen and methane coproduction potential. This technique represents a promising method for improving cellulosic biomass biodegradation and green energy coproduction.