Glycerol electrooxidation on Pd,Pt and Au nanoparticles supported on carbon ceramic electrode in alkaline media

In the present study, electrooxidation of glycerol was investigated on Au, Pd and Pt nanoparticles modified carbon ceramic electrode (CCE) by using different electrochemical techniques such as: Cyclic voltammetry (CV), Chronoamperometry (CA), Chronopotentiometry (CP) and Electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were also employed to physicochemical survey of the electrocatalysts. The kinetic parameters of glycerol oxidation, i.e. Tafel slope and activation energy (E_a), were determined on the modified electrodes. The Tafel slopes of 166 mV dec⁻¹ on Pt|CCE, 177 mV dec⁻¹ on Au|CCE and 136 mV dec⁻¹ on Pd|CCE were obtained. The lowest E_a value of 11.2 kJ mol⁻¹ was calculated on Au|CCE. In continuation, the reaction orders with respect to the glycerol and NaOH concentrations on Pd|CCE were found to be 0.27 and 0.87, respectively. The CV, CP and CA results showed remarkable electrocatalytic activity and good poisoning tolerance of Au|CCE for glycerol oxidation.     

Parametric study on electrochemical reforming of glycerol for hydrogen production

Hydrogen production by electrochemical reforming of glycerol was investigated in this study. Within this scope, the performance of the system under different operating conditions was evaluated by parametric studies and optimum operating conditions were determined. The effects of membrane type, membrane pre-treatment procedure and temperature were investigated. System performance was examined also with long-term tests. The formation of hydrogen at the cathode was determined by analyzing the product gases by gas chromatography. Optimum condition for maximum hydrogen production was obtained with the Zn/Zn electrode pair in the presence of 0.4 M glycerol and 0.04 M H₂SO₄ at the anode side, 0.04 M H₂SO₄ at the cathode side and with pre-treated Nafion XL membrane. As the result of performance tests, room temperature and 2 V potential were found to be the most suitable operating conditions.     

Catalytic activities of Ag/C decorated with small amounts of Au and Pt for glycerol oxidation

The two-step decoration of the Ag nanoparticles supported on carbon black (Ag/C) with Au and Pt, the electrooxidation of glycerol on the Pt/Au/Ag/C catalysts in alkaline solution, and the effect of the amounts of Au and Pt on the catalytic activity of Pt/Au/Ag/C are investigated. The decoration of Ag/C is performed by electrochemically depositing a small amount of Au and then Pt on Ag/C, and the Pt_x/Au_y/Ag₁₀₀/C catalysts with different x:y:100 ratios (0.15 ≤ x ≤ 1.9 and 0.2 ≤ y ≤ 1.5) are obtained. Physical and electrochemical characterizations reveal that small parts of the Ag surfaces are covered by the deposited Au and Pt. Pt_x/Au_y/Ag₁₀₀/C mainly shows Pt-relevant behaviors in glycerol oxidation, and Pt_1.3/Au_y/Ag₁₀₀/C exhibits high catalytic activities. The results reveal that the surface decoration is a useful method of fabricating efficient ternary catalysts at low cost.     

Autothermal steam reforming of glycerol for hydrogen production over packed-bed and Pd/Ag alloy membrane reactors

In this study, glycerol, with its high H/C ratio feature, was steam reformed with oxygen to produce hydrogen in packed-bed and Pd/Ag membrane reactors. The addition of oxygen, which causes the partial oxidation, was to achieve thermal neutral for the energy saving purposes.     

Tailor-designed bimetallic Co/Ni macroporous electrocatalyst for efficient glycerol oxidation and water electrolysis

Water electrolysis is broadly considered one of the most promising technologies for green hydrogen production. However, the oxygen evolution reaction (OER) is thermodynamically unfavorable and requires large overpotentials to proceed with an adequate rate. Herein, we introduce key structural and compositional parameters controlling the hydrogen evolution reaction (HER) performance of a representative family of bimetallic CoNi porous electrocatalysts and highlight a simple strategy for replacing the OER with glycerol oxidation reaction (GOR) to reduce the input cell voltage. The structural, morphological, and electrochemical characterizations of a series of electrocatalysts, prepared by the dynamic hydrogen bubble template technique (DHBT), were fully studied which reveals that changing of Co: Ni ratio affects HER activity. Optimization of this ratio leads to enhancement in both intrinsic and mass activity besides the high density of accessible active sites. This, in turn, leads to an efficient electrocatalyst achieving a low overpotential of ?67 mV at a current density of 10 mA/cm² during HER. As a bifunctional electrocatalyst, it requires only 1.65 V to deliver the same current density with excellent stability for more than 20 h of continuous water electrolysis in alkaline medium. Moreover, the input cell voltage drops by at least 0.2 V during glycerol electrolysis with concurrent production of both hydrogen and value-added chemicals especially hydroxy pyruvate ion.     

A new analysis of two phase flow on hydrogen production from water electrolysis

It is clear that the entire world have to research, develop, demonstrate and plan for alternative energy systems for shorter term and also longer term. As a clean energy carrier, hydrogen has become increasingly important. It owes its prestige to the increase within the energy costs as a result of the equivocalness in the future availability. Two phase flow and hydrogen gas flow dynamics effect on performance of water electrolysis. Hydrogen bubbles are recognized to influence energy and mass transfer in gas-evolving electrodes. The movement of hydrogen bubbles on the electrodes in alkaline electrolysis is known to affect the reaction efficiency. Within the scope of this research, a physical modeling for the alkaline electrolysis is determined and the studies about the two-phase flow model are carried out for this model. Internal and external forces acting on the resulting bubbles are also determined. In this research, the analytical solution of two-phase flow analysis of hydrogen in the electrolysis is analyzed.     

Fabrication and characterization of NiCoZn-M (M: Ag, Pd and Pt) electrocatalysts as cathode materials for electrochemical hydrogen production

Ag, Pd and Pt-modified alkaline leached NiCoZn composite coatings were prepared on a copper specimen by electrochemical technique. The chemical composition of layers before and after leaching as well as after noble metal modification was determined by energy dispersive X-ray spectroscopy (EDX). The surface morphologies of the composite coatings were examined with the help of scanning electron microscopy (SEM). The hydrogen evolution activity of the electrodes was studied in 1 M KOH solution. For this purpose, cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques were used. Furthermore, the change of hydrogen evolution activity of the electrodes as a function of operation time in alkaline solution was also investigated. Surface morphologies showed that the composite coatings prepared to have compact and porous surface. EDX analysis confirmed the presence of Ag, Pd and Pt metals over the NiCoZn layer. The co-deposition of nickel, cobalt and zinc on copper surface and subsequently alkaline leaching of zinc rendered cathode material very active in hydrogen evolution. The modification of alkaline leached NiCoZn ternary coating by deposition of small amounts of Ag, Pd and Pt can further enhance the hydrogen evolution performance of this Raney-type electrode when compared to NiCoZn individually. The order of hydrogen evolution activity of catalysts studied is Ni < NiCoZn < NiCoZn-Pd < NiCoZn-Ag < NiCoZn-Pt. The long-term electrolysis tests showed that the Pt-modified electrode has the better time stability than the others. The superiority of Pt-modified catalyst explained by well known intrinsic catalytic activity of Pt.     

CuFe electrocatalyst for hydrogen evolution reaction in alkaline electrolysis

The development of high performance, stable catalyst with non-precious metals for electrochemical hydrogen evolution reaction for alkaline electrolysis is in demand. Here-in, we report the synthesis of CuFe layered double hydroxide (LDH) electrocatalyst on nickel foam via facile hydrothermal method. In alkaline electrolysis with 1 M NaOH electrolyte, CuFe LDH as cathode requires an overpotential of 159 mV to generate current density of 10 mA cm⁻². Which is ca. 51 mV and 7 mV lower than NiFe LDH and NiRu LDH. CuFe LDH exhibits significant electrocatalytic activity for HER. The higher catalytic activity of CuFe LDH compared to NiFe LDH may be achieved with higher proton adsorption by Cu compared to Ni. Also, the efficient charge transfer with interconnected LDH layers, favourable three dimensional structure facilitating easy electrolyte transfer to the active sites and hydrogen gas diffusion. This work may help in developing low cost and efficient hydroxide catalyst.     

Effects of attapulgite-supported transition metals catalysts on glycerol steam reforming for hydrogen production

The attapulgite supported transition metals (Ni, Cu, Co or Fe) catalysts were prepared by precipitation method at constant loading (10 wt%) and investigated in the glycerol steam reforming reaction for H₂ production under 400–750 °C, water/glycerol (W/G) = 3, N₂ flow ratio = 0.16 L/min and WHSV = 6.46 h^?1. The as-prepared catalysts were characterized by N₂ adsorption-desorption, XRD, H₂-TPR and TEM-EDS. The results shown different active metals presented various crystalline sizes and reduction properties. The experimental results revealed Ni/ATP and Co/ATP catalysts had more active for glycerol steam reforming than Cu/ATP and Fe/ATP catalysts, due to the fact that active metal Ni and Co have superior capacity to promote the necessary CC rupture and facilitate the water gas shift reaction. In addition, the results revealed that CH₄ production was favored at low temperatures while CO production was presented at high temperatures, which were induced by the different reaction networks over catalysts. In addition, the stability test shown all catalysts had different various degrees of inactivation, resulting from the sintering of active metals and carbon deposition. The characterizations of XRD, TEM and TG-DTG for spent catalysts revealed the smallest amount of carbon deposited for Cu/ATP, which was attributed to the lowest Cu particle size. Additionally, two different types of carbon was found, namely filamentous carbon for Ni and Co/ATP and encapsulating carbon for Cu and Fe/ATP.     

Hydrogen generation by electrolysis under subcritical water condition and the effect of aluminium anode

The productions of catalytic active materials and the reactor designs increasing the kinetics of the system are very important because of efficient energy production for electrolysis systems. In this study, the effects of subcritical water's conditions on electrolysis were investigated. All experiments were carried out under the subcritical water conditions, high temperature and pressure resistant reactor was used and the three electrodes were integrated in to the reactor. The aluminium anode was used to prevent the formation of oxygen in the reactor during obtaining pure hydrogen gas. The effect of pure (Al), Al-6013 and Al-7075 aluminium anodes on the electrolysis of water were investigated and compared with Pt anode. For all electrodes, Pt was used as cathode and Ag/AgCl electrode was used as reference electrode. Electrochemical Impedance Spectroscopy (EIS) measurements, current potential measurements were managed at −2 V, electrolysis current at 2 V constant potential during 1800 s was being followed and gas volume produced was measured to determine the most efficient aluminium anode. Energy consumption and hydrogen gases efficiency were also calculated for 25 °C room temperature. After determining the most efficient aluminium anode, the experiments were repeated in the subcritical water environment. Nitrogen gas was used to purge the system. The temperature was 130 °C and the pressure was 20 Bar. As a result, the use of aluminium alloys as an anode under the subcritical water conditions reduced energy consumption from 1400 kJ mol⁻¹ to 300 kJ mol⁻¹. The current density was increased to 370 mA cm⁻² at 2 V. The efficiency increase from %15 to %70, and the amount of hydrogen gas produced was increase from 18 mL cm⁻² h⁻ to 300 mL cm⁻² h⁻. In addition, using the aluminium anode eliminated the gas separation processes by providing purer hydrogen gas production.     

Cobalt doping VS2 on nickel foam as a high efficient electrocatalyst for hydrogen evolution reaction

The development of non-precious metal catalysts with abundant reserves, low prices and good performance for HER is desired. In this work, rodlike Co doping VS₂ arrays on nickel foam (NF) (Co-VS₂/NF) were fabricated by a simple one-step solvothermal method. Structure characterization indicated that Co doping reduced the size of rodlike Co-VS₂ and meanwhile can modulate its electronic structure, which is beneficial for the enhancement of HER performance. The optimal Co-VS₂/NF-2 reveals a low overpotential of 164.5 mV at ?10 mA cm^?2, small Tafel slope of 52.2 mV dec^?1 and excellent long-term stability after 2000 cycles in 1 M KOH.     

A study of combined biomass gasification and electrolysis for hydrogen production

An integrated system for the production of hydrogen by gasification of biomass and electrolysis of water has been designed and cost estimated. The electrolyser provides part of the hydrogen product as well as the oxygen required for the oxygen blown gasifier. The production cost was estimated to 39 SEK/kg H₂ at an annual production rate of 15?000 ton, assuming 10% interest rate and an economic lifetime of 15 years. Employing gasification only to produce the same amount of hydrogen, leads to a cost figure of 37 SEK/kg H₂, and for an electrolyser only a production cost of 41 SEK/kg H₂. The distribution of capital and operating cost is quite different for the three options and a sensitivity analyses was performed for all of these. However, the lowest cost hydrogen produced with either method is at least twice as expensive as hydrogen from natural gas steam reforming.     

A critical review on cathode materials for steam electrolysis in solid oxide electrolysis

The major technologies being considered for the green hydrogen production are polymer electrolyte membrane (PEM) and solid oxide electrolysis (SOE). While PEM electrolysis technology is nearing commercialisation with units now being globally installed at tens of MW scale, SOE technology is still under development with units available only at 100s of kW scale and at much higher costs per kW. SOE due to its high operating temperatures (close to 800 °C) has the potential to reduce the electric energy input by up to 30% for the hydrogen production per tonne by using the low-cost thermal energy input available from the industrial or downstream synthesis processes. The SOE cathode, where steam electrolysis occurs, plays a crucial role in dictating the cell voltage losses and the stability of the cell operation that eventually has a large impact on the SOE efficiency and lifetime. The current state-of-the-art cathode materials based on Ni-YSZ pose many challenges. There is, therefore, a global effort to find alternative cathode materials suitable for steam electrolysis in SOE. This review critically reviews novel nanoengineered cathode materials and points to the fact that such materials synthesized using infiltration and exsolution techniques, in combination with advanced materials characterisation like high-temperature scanning probe microscopy and in situ Raman spectroscopy can be a right approach to find the suitable cathode materials for steam electrolysis in SOE. This, however, may need to be combined with a techno-economic analysis to provide the technical and economic viability of these materials for the SOE commercialisation.     

Hydrogen production from glycerol steam reforming over nickel catalysts supported on alumina and niobia: Deactivation process,effect of reaction conditions and kinetic modeling

Ni catalysts were prepared by wet impregnation of three different supports: alumina, niobia and 10 wt.% niobia/alumina, prepared by (co)precipitation. The catalysts were evaluated on steam reforming of glycerol at 500 °C, for 30 h. The catalyst supported on Nb₂O₅/Al₂O₃ presented the best performance, with higher conversion into gas (80%) during all reaction time and hydrogen yield of 50%. Alumina supported catalyst showed higher deactivation and lower hydrogen yield. All catalysts showed coke formation, but it was formed in larger amount on the catalysts supported on single oxides. A depth study was conducted to evaluate the effect of reaction variables as space velocity, glycerol concentration in feed and temperature on the catalytic performance of the Nb₂O₅/Al₂O₃ catalyst. Kinetic study was also performed for this catalyst using two different approaches, obtaining glycerol and steam orders, as well as the apparent activation energy.     

One-step CO assisted synthesis of hierarchical porous PdRuCu nanosheets as advanced bifunctional catalysts for hydrogen evolution and glycerol oxidation

Pd-based catalysts have received wide attention due to their outstanding anti-CO poisoning property, whereas the structural instability limits their application. The hierarchical porous PdRuCu nanosheets (HP PdRuCu NSs) with large electrochemically active surface area, abundant active sites, and stable structures are synthesized through continuous access to CO bubbles. HP PdRuCu NSs exhibit excellent hydrogen evolution reaction (HER) catalytic activity with an ultralow overpotential of 25 mV at 10 mA cm^?2 and a Tafel slope of 87.5 mV dec^?1 in alkaline·media. Meanwhile, the peak mass activity and specific activity of HP PdRuCu NSs for glycerol oxidation reaction (GOR) are 1083 mA mg^?1_Pd and 38.8 A m^?2, respectively, superior to that of PdRu nanosheets (PdRu NSs), Pd nanosheets (Pd NSs), and commercial Pd black. The introduction of Ru and Cu atoms facilitates the C–C bond cleavage and the complete oxidation of glycerol to CO₂, as well as the accelerated oxidation/removal of the poisonous CO_ads in between.     

Steam electrolysis performance of intermediate-temperature solid oxide electrolysis cell and efficiency of hydrogen production system at 300 Nm h

The steam electrolysis performance of an intermediate-temperature solid oxide electrolysis cell (SOEC) was measured at 650 °C at various steam concentrations. The cell voltage decreased with increasing steam concentration, which was attributed to a decrease in the steam electrode polarization. The highest performance of the SOEC was 1.32 V at 0.57 A cm⁻². On the basis of the electrolytic characteristics of this cell, the efficiency of a hydrogen production system operating at a capacity of 300 N m³ h⁻¹ was estimated. The system efficiency reached a higher heating value (HHV standard) of 98% due to the effective recovery of thermal energy from exhaust gas.     

A high temperature and pressure framework for supercritical water electrolysis

Water electrolysis technologies aim to provide a significant increase in green hydrogen production efficiency. In this work, a framework was developed to explore the use of supercritical water for alkaline electrolysis. This framework was used to perform Arrhenius analysis as a function of potential, and to explore activation energies for sub- and supercritical water electrolysis. An analysis of the conductivity of solution unveiled a discontinuity in the trends between sub- and supercritical potassium hydroxide solution conductivity. Unlike prior work on supercritical water electrolysis, this work investigates trends in electrochemical parameters, the sources of these trends, and how they change between the sub- and supercritical regimes.     

Amorphous CoFeB on nickel foam as a high efficient electrocatalyst for hydrogen evolution reaction

The development of high-performance, low cost and earth abundant catalysts for hydrogen evolution reaction (HER) is desired. This work presents amorphous CoFeB supported on nickel foam (NF), prepared by a facial chemical reduction method, as an active catalyst for HER in alkaline solution. Structure characterization indicated that with the incorporation of Fe atom, CoFeB catalysts exhibit similar petal-like granular morphology as CoB. The optimal CoFeB/NF-0.15 catalyst exhibits Brunauer-Emmett-Teller (BET) surface area of 27.4 m² g^?1, nearly two times larger than 13.2 m² g^?1 for CoB, suggesting higher specific surface area. CoFeB/NF-0.15 catalyst shows excellent HER performance and reaches ?10 mA cm^?2 at overpotential of 35 mV in alkaline solution, and Tafel slope of 84.7 mV dec^?1, indicative of Volmer-Heyrovsky reaction mechanism. The synergistic effect among Fe, Co and B atoms and the more exposed active sites as well as faster electron transfer kinetics collectively contributed to the improved intrinsic activity of CoFeB for HER. Moreover, CoFeB/NF-0.15 exhibits good stability for over 16 h.     

Economic and environmental competitiveness of high temperature electrolysis for hydrogen production

Alternative hydrogen production technologies are sought in part to reduce the greenhouse gas (GHG) emissions intensity compared with Steam Methane Reforming (SMR), currently the most commonly employed hydrogen production technology globally. This study investigates hydrogen production via High Temperature Steam Electrolysis (HTSE) in terms of GHG emissions and cost of hydrogen production using a combination of Aspen HYSYS® modelling and life cycle assessment. Results show that HTSE yields life cycle GHG emissions from 3 to 20 kg CO_2e/kg H₂ and costs from $2.5 to 5/kg H₂, depending on the system parameters (e.g., energy source). A carbon price of $360/tonne CO_2e is estimated to be required to make HTSE economically competitive with SMR. This is estimated to potentially decrease to $50/tonne CO_2e with future technology advancements (e.g., fuel cell lifetime). The study offers insights for technology developers seeking to improve HTSE, and policy makers for decisions such as considering support for development of hydrogen production technologies.     

The theoretical study of the bimetallic Ni/Pd,Ni/Pt and Pt/Pd catalysts for hydrogen spillover on penta-graphene

The catalytic property of the bimetallic Ni/Pd, Ni/Pt and Pt/Pd particles for hydrogen spillover on penta-graphene (PG) are studied by using the first-principles and kinetic Monte Carlo (KMC) calculations. The bimetallic Ni/Pd, Ni/Pt and Pt/Pd particles can be stably decorated on PG surface with binding energies in the range of 4.15–5.52 eV. The adsorption enthalpies of H₂ molecules on bimetallic particles are in the range of ?11.56–?15.35 kcal/mol. The H atom can migrate from the bimetallic particles to PG with the migration barriers range from 0.67 to 0.95 eV. The KMC simulations show that the hydrogen spillover reactions can occur at a suitable temperature (260–361 K), which meet DOE target for onboard hydrogen storage systems applied to light-duty vehicles. In the study, the highest occupied molecular orbital and electric field analysis shows that the bimetal mixing can reduce the hydrogen adsorption enthalpy, and thereby reduce the H migration barrier, which displays a synergistic effect for hydrogen spillover.