Electrodes For Hydrogen Production Research Articles

Electrochemical hydrogen production of SS, Ni, and Ni-B electrodes in prototype electrolyzer system

Highly efficient, low-cost, and stable electrocatalysts are crucial in electrocatalytic water splitting. Herein, the comparative study of stainless steel (SS), a Nickel (Ni/SS), and Nickel boride (Ni-B/SS) electrode for hydrogen production was carried out under a prototype electrolyzer system. The Ni/SS and Ni-B/SS were synthesized by a simple and low-cost chemical method on the SS substrate. As compared to SS and Ni/SS electrodes, the Ni-B/SS electrode demonstrates superior electrochemical activity towards the Hydrogen Evolution reaction (HER) with a low overpotential of 75 mV at a current density of 10 mA/cm2 and Tafel slope of 82 mV/dec in 1M KOH electrolyte. The as-fabricated Ni-B/SS electrode showed cauliflower-like morphology and exhibited an excellent hydrogen production rate such as 4.39 ml/min on a (2 cm x 2 cm) electrode at a constant potential of 2.2 V in a prototype electrochemical hydrogen production setup. The stability of the Ni-B/SS (6 cm x 6 cm) electrode was also checked on a large-scale prototype electrolyzer setup for 50 hr at a constant potential.

Behavior of a forest of NiFe nanowires in KOH and NaCl solution for water electrolysis

The present work investigates the behavior of nanostructured electrodes consisting of an array of nanowires of NiFe alloy in KOH + 0.5 M NaCl solution. The aim is to explore the possibility of using these electrodes for hydrogen production by seawater electrolysis. Seawater splitting requires a highly selective electrode on the anode side, where the evolution of molecular chlorine or the formation of other active chlorine compounds can compete with the oxygen evolution reaction. Nanostructured electrodes, obtained by template electrosynthesis, were tested at room temperature in KOH + 0.5 M NaCl solution, and the results were compared with those obtained in pure KOH. The results showed that the presence of NaCl does not affect the electrocatalytic behavior of the nanostructured NiFe alloy. Furthermore, the chemical–physical characterizations carried out after the long-term galvanostatic tests, have shown that the nanostructured electrodes are also stable in terms of morphology and composition. In addition, the solution used to perform the long-term galvanostatic tests was analyzed to investigate the possible formation of chlorine compounds. The absence of these compounds, together with the measured potential value measured for the oxygen evolution reaction, which was always lower than the thermodynamic redox potential for the hypochlorite formation reaction, leads us to conclude that these electrodes are potentially suitable for seawater electrolysis.

Casting of high surface area electrodes enabled by low-temperature welding of copper nanoporous powders and nanoparticles hybrid feedstocks

Nanoporous metallic powders are proposed as electrodes for hydrogen production, current collectors in batteries, or active material in propellants to overcome limitations in reaction kinetics of their bulk solid counterpart. However, their consolidation into 3D parts via powder metallurgy while maintaining high mechanical performance is limited by their thermodynamic instability during sintering and poor flowability. This paper demonstrates the synthesis of spherical nanoporous copper powders (PCu) via dealloying of Cu-Al gas-atomized precursors with high-throughput (i.e., 0.1 kg/hr), moderate flowability (i.e., Carney flowrate of 32.9 s/50 g), moderate-oxygen content (i.e., < 12 at.%), high-surface area (∼12 m2/g) and free of precipitates. The nanoscale weldability of hybrid feedstocks composed of PCu (65.5 – 91.2 vol.%) and copper nanoparticles (8.8 – 34.5 vol.%) were harvested to sinter them at temperatures as low as a third of its melting point and overcome the metastability of PCu to preserve its high-surface area. Open-die casting in reducing atmospheres was employed at temperatures between 300 – 700 °C resulting in parts with ultimate compression strength of 3.6 – 17.8 MPa while forming electrically conductive solids with preserved nanoporosity (i.e., pore size 24 – 36 nm). Such feedstocks may be integrated with powder-based manufacturing processes such as powder injection molding and additive manufacturing to produce complex architectures.

Towards a circular economy for Pt catalysts. Case study: Pt recovery from electrodes for hydrogen production

This work links two challenges that our society is facing nowadays, the climate change and the scarcity of key raw materials as the platinum group materials are. Hence, Pt from membrane electrode assemblies used in the well-known Westinghouse cycle for hydrogen production has been successfully recovered using the selective electrochemical dissolution process and reaching global efficiencies of 70 wt%. Pt electrocatalysts were synthesized from the Pt recovered from the spent electrodes and characterized. Thus, the scanning electrochemical microscopy technique demonstrated that Pt was well dispersed onto the carbon support. Moreover, electrodes with both, commercial and recovered Pt/C catalysts were prepared and tested. The electrodes with the catalyst prepared from the spent MEAs show a good activity towards the SO2 oxidation, the reaction for H2 production, and above all, a very high stability. In conclusion, the circular economy of Pt based catalyst for a H2 production process has been achieved.

Towards a Circular Economy for Pt Catalysts. Case Study: Pt Recovery from Electrodes for Hydrogen Production

Towards a Circular Economy for Pt Catalysts. Case Study: Pt Recovery from Electrodes for Hydrogen Production

Graphite Electrodes for Hydrogen Production by Acid Electrolysis

Nowadays, humanity has become aware of the consequences that the use of fossil fuels entails, and the latest developments in the energy sector are leading to a diversification of energy resources. In this context, researching on alternative forms of producing electric energy is being conducted. At the transportation level, a possible solution for this matter may lie in hydrogen fuel cells. The electrolysis of water is one of the possible processes for hydrogen production, but the reaction to break the water molecule requires a great amount of energy and this is precisely the biggest issue involving this process. In this work, low cost electrodes of 254 stainless steel and electrolytic graphite were used for hydrogen production, allowing high efficiency and reduced oxidation during the process. The selection of these materials allows to obtain a high corrosion resistance electrolytic pair, by replacing the high cost platinum electrode usually employed in the alkaline electrolysis process. The formic acid of biomass origin was used as an electrolyte. It was observed that the developed reactor have no energy losses through heat and it was possible to obtain approximately 82% conversion efficiency in the gas production process.

Highly Efficient Hybrid Ni/Nitrogenated Graphene Electrocatalysts for Hydrogen Evolution Reaction.

Two nickel/nitrogenated graphene hybrid electrodes (Ni-NrGONH3 and Ni-NrGOAPTES) were synthesized, and their catalytic activity with respect to the hydrogen evolution reaction (HER) in alkaline media was analyzed. Incorporation of nitrogen to the carbon structure in graphene oxide (GO) or reduced GO (rGO) flakes in aqueous solutions was carried out based on two different configurations. NrGONH3 particles were obtained by a hydrothermal method using ammonium hydroxide as the precursor, and NGOAPTES particles were obtained by silanization (APTES functionalization) of GO sheets. Aqueous dispersions containing NrGONH3 and NGOAPTES particles were added to the traditional nickel Watts plating bath in order to prepare the Ni-NrGONH3 and Ni-NrGOAPTES catalysts, respectively. Nickel substrates were coated with the hybrid nickel electrodeposits and used as electrodes for hydrogen production. The Ni-NrGO catalysts show a higher activity than the conventional nickel electrodeposited electrodes, particularly the ones containing APTES molecules because they allow obtaining a hydrogen current density 130% higher than conventional Ni-plated electrodes with a Watts bath in the absence of additives. In addition, both catalysts show a low deactivation rate during the ageing treatment, which is a sign of a longer midlife for the catalyst. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were used for examination of the catalytic efficiency of hybrid Ni-NrGO electrodes for HER in KOH solution. High values of exchange current densities, 8.53 × 10–4 and 2.53 × 10–5 mA cm–2 for HER in alkaline solutions on Ni-NrGONH3 and Ni-NrGOAPTES electrodes, respectively, were obtained.

Effect of carbon coating on Cu electrodes for hydrogen production by water splitting

In recent years, fossil fuel depletion has been increasing, which leads to environmental issues. Hydrogen energy is considered a promising renewable energy to replace fossil fuels because it is a sustainable, clean, and green energy source. Among hydrogen production methods, water splitting has the highest reliability and is used the most often. Platinum is normally used as water splitting catalyst and an electrode. However, there has been much effort to replace it as such owing to its high cost. Copper (Cu) is not used as water splitting catalyst or an electrode, despite its high current density, because of its corrosive properties. In this study, carbon was coated onto a Cu substrate and a hydrogen production experiment was carried out with 0.1 M Na2SO4 and 0.1 M H2SO4 electrolytes. As a result, the carbon coating decreased oxidation rate of the Cu electrode and effected stability in short-term hydrogen evolution experiment. This indicates the possibility of carbon-Cu electrode with other catalytic materials.

Exfoliated molybdenum di-sulfide (MoS2) electrode for hydrogen production in microbial electrolysis cell

The most widely reported catalyst in microbial electrochemical cells (MEC) cathodes is platinum (Pt). The disadvantages of Pt include its high cost and sensitivity to various molecules. In this research an exfoliated molybdenum di-sulfide (MoS2-EF) catalyst was synthesized. The size of the obtained particles was 200 ± 50 nm, 50-fold smaller than the pristine MoS2 catalyst. The MoS2-EF Raman spectrum displays the E12g and A1g peaks at 373 cm−1 and 399 cm−1. Electrochemical characterization by linear sweep voltammetry (LSV) of a rotating disc electrode RDE showed that the current density of Pt in 0.5 M H2SO4 was 3.3 times higher than MoS2-EF. However, in phosphate buffer (pH-7) electrolyte this ratio diminished to 1.9. The polarization curve of Pt, MoS2-EF and the pristine MoS2 electrodes, at −1.3 V in MEC configuration in abiotic conditions exhibit current densities of 17.46, 12.67 and 3.09 mA cm−2, respectively. Hydrogen evolution rates in the same MEC with a Geobacter sulfurreducens anode and Pt, MoS2-EF and the pristine MoS2 cathodes were 0.106, 0.133 and 0.083 m3 d−1 m−3, respectively.The results in this study show that MoS2-EF led to highly purified hydrogen and that this catalyst can serve as an electrochemical active and cost-effective alternative to Pt.

Ternary Platinum-Copper-Nickel Nanoparticles Anchored to Hierarchical Carbon Supports as Free-Standing Hydrogen Evolution Electrodes.

Developing cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts for hydrogen production is of paramount importance to attain a sustainable energy future. Reported herein is a novel three-dimensional hierarchical architectured electrocatalyst, consisting of platinum-copper-nickel nanoparticles-decorated carbon nanofiber arrays, which are conformally assembled on carbon felt fabrics (PtCuNi/CNF@CF) by an ambient-pressure chemical vapor deposition coupled with a spontaneous galvanic replacement reaction. The free-standing PtCuNi/CNF@CF monolith exhibits high porosities, a well-defined geometry shape, outstanding electron conductivity, and a unique characteristic of localizing platinum-copper-nickel nanoparticles in the tips of carbon nanofibers. Such features render PtCuNi/CNF@CF as an ideal binder-free HER electrode for hydrogen production. Electrochemical measurements demonstrate that the PtCuNi/CNF@CF possesses superior intrinsic activity as well as mass-specific activity in comparison with the state-of-the-art Pt/C catalysts, both in acidic and alkaline solutions. With well-tuned composition of active nanoparticles, Pt42Cu57Ni1/CNF@CF showed excellent durability. The synthesis strategy reported in this work is likely to pave a new route for fabricating free-standing hierarchical electrodes for electrochemical devices.

Synthesis and Structure of Titania Nanotubes For Hydrogen Generation

Titania nanotubes (TiO2NTs) working electrodes for hydrogen production by photoelectrocatalytic water splitting were synthesized by means of anodization method. The electrolytes were the mixtures of oxalic acid (H2C2O4), ammonium fluoride (NH4F), and sodium sulphate (VI) (Na2SO4) with different pHs. A constant dc power supply at 20 V was used as anodic voltage. The samples were annealed at 450 °C for 2 hrs. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to characterized TiO2NTs microstructure. TiO2NTs with diameter of 100 nm were obtained when pH 3 electrolyte consisting of 0.08 M oxalic acid, 0.5 wt% NH4F, and 1.0 wt% Na2SO4was used. Without external applied potential, the maximum photocurrent density was 2.8 mA/cm2under illumination of 100 mW/cm2. Hydrogen was generated at an overall photoconversion efficiency of 3.4 %.

A photoelectrochemical investigation of the hydrogen-evolving doped TiO 2 nanotube arrays electrode

The present work investigates the photoelectrochemical behavior of nanotubular N/C-TiO 2 electrode for hydrogen production. Via the sonoelectrochemical anodization process of 1 h, N-containing TiO 2 based nanotube arrays(N-TNT) with the length of about 650 nm were fabricated in fluoride aqueous solution added 0.25 M NH 4NO 3; C-containing TiO 2 based nanotube arrays(C-TNT) with the length of about 2 μm were prepared in fluoride ethylene glycol solution. In virtue of the longer tubes with the larger surface areas, C-TNT can harvest more light and produce more photoactive sites than N-TNT, which also made the charge transfer resistance in C-TNT larger than that in N-TNT. Considered the more negative flat band potential of C-TNT, C-TNT has the smaller energy barrier and the better photoelectrochemical activity. It may be attributed to the appropriate defect concentration gradient owing to the modification of C element. Under UV–vis light (320–780 nm) irradiation, the average hydrogen generation rate of C-TNT was 282 μL h −1 cm −2. The surface properties and near-surface properties of the resultant electrode were synthetically analyzed by using UV–vis diffuse reflectance spectra(DRS), field emission scanning electron microscopy (FESEM), I-t curves, and electrochemical impedance spectroscopy (EIS) techniques.

Simultaneous Hydrogen Production and Electrochemical Oxidation of Organics Using Boron-Doped Diamond Electrodes

This paper presents advantages of using a boron-doped diamond (BDD) electrode for hydrogen production and wastewater treatment in a single electrochemical cell. Results indicated that the BDD electrode possessed the widest known electrochemical window, allowing new possibilities for both anodic and cathodic reactions to simultaneously take place. The BDD electrode exhibited high anodic potential, generating high oxidation state radicals that facilitated oxidation of toxic waste organic compounds such as 4-nitrophenols. In contrast, because of widening of potential windows, the rate of hydrogen evolution at the cathode was significantly increased. Time-on-stream concentrations of reaction intermediates were monitored to elucidate mechanism involved in 4-nitrophenol oxidation. Spalling, fouling, or reduction in the thickness of thin-film diamond coating was not observed. Overall, the BDD electrode exhibits unique properties including chemical inertness, anticorrosion, and extended service life. These properties are especially important in wastewater treatment. Economic advantages were attributed to the low cost and long duration BDD electrode and the valuable hydrogen byproduct produced. Analysis has shown that technology associated with the BDD electrode could be effectively implemented with minimum energy input and capital requirements. When combined with solar energy and fuel cells, electrochemical wastewater processing can become energy efficient and cost-effective.

Effects of sputtering conditions on electrochemical behavior and physical properties of Ni-Mo alloy electrode

Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical behavior of electrode were characterized by steady-state polarization plot and Tafel polarization curve measurements. And the physical properties of electrodes were characterized by XRD, SEM, AFM and EDS. It is found that the overpotential is significantly influenced by the working pressure which affects critically the electrode surface morphology, and two Tafel regions are observed for each sample. The overpotential value does not change very much with the substrate temperature. The XRD results indicates that the electrodes should be considered nanocrystalline. Thornton model for the microstructure of sputter-deposited electrodes is referred to explain the observed microstructure change.