Production & Supply Chain
Electrocatalyst Derived from NiCu–MOF Arrays on Graphene Oxide Modified Carbon Cloth for Water Splitting
Apr 2022
Publication
Electrocatalysts are capable of transforming water into hydrogen oxygen and therefore into energy in an environmentally friendly and sustainable manner. However the limitations in the research of high performance catalysts act as an obstructer in the development of using water as green energy. Here we report on a delicate method to prepare novel bimetallic metal organic framework derived electrocatalysts (C–NiCu–BDC–GO–CC) using graphene oxide (GO) modified carbon cloth as a 3D flexible and conductive substrate. The resultant electrocatalyst C–NiCu–BDC– GO–CC exhibited very low electron transfer resistance which benefited from its extremely thin 3D sponge-like morphology. Furthermore it showed excellent oxygen evolution reaction (OER) activity achieving 10 mA/cm2 at a low overpotential of 390 mV in 1 M KOH electrolyte with a remarkable durability of 10 h.
Theoretical Insights into the Hydrogen Evolution Reaction on the Ni3N Electrocatalyst
Jun 2021
Publication
Ni-based catalysts are attractive alternatives to noble metal electrocatalysts for the hydrogen evolution reaction (HER). Herein we present a dispersion-corrected density functional theory (DFT-D3) insight into HER activity on the (111) (110) (001) and (100) surfaces of metallic nickel nitride (Ni3N). A combination of water and hydrogen adsorption was used to model the electrode interactions within the water splitting cell. Surface energies were used to characterise the stabilities of the Ni3N surfaces along with adsorption energies to determine preferable sites for adsorbate interactions. The surface stability order was found to be (111) < (100) < (001) < (110) with calculated surface energies of 2.10 2.27 2.37 and 2.38 Jm−2 respectively. Water adsorption was found to be exothermic at all surfaces and most favourable on the (111) surface with Eads = −0.79 eV followed closely by the (100) (110) and (001) surfaces at −0.66 −0.65 and −0.56 eV respectively. The water splitting reaction was investigated at each surface to determine the rate determining Volmer step and the activation energies (Ea) for alkaline HER which has thus far not been studied in detail for Ni3N. The Ea values for water splitting on the Ni3N surfaces were predicted in the order (001) < (111) < (110) < (100) which were 0.17 0.73 1.11 and 1.60 eV respectively overall showing the (001) surface to be most active for the Volmer step of water dissociation. Active hydrogen adsorption sites are also presented for acidic HER evaluated through the ΔGH descriptor. The (110) surface was shown to have an extremely active Ni–N bridging site with ΔGH = −0.05 eV.
Recent Progress and Approaches on Transition Metal Chalcogenides for Hydrogen Production
Dec 2021
Publication
Development of efficient and affordable photocatalysts is of great significance for energy production and environmental sustainability. Transition metal chalcogenides (TMCs) with particle sizes in the 1–100 nm have been used for various applications such as photocatalysis photovoltaic and energy storage due to their quantum confinement effect optoelectronic behavior and their stability. In particular TMCs and their heterostructures have great potential as an emerging inexpensive and sustainable alternative to metal-based catalysts for hydrogen evolution. Herein the methods used for the fabrication of TMCs characterization techniques employed and the different methods of solar hydrogen production by using different TMCs as photocatalyst are reviewed. This review provides a summary of TMC photocatalysts for hydrogen production.
Dynamic modelling of a direct internal reforming solid oxide fuel cell stack based on single cell experiments
May 2018
Publication
Direct internal reforming enables optimal heat integration and reduced complexity in solid oxide fuel cell (SOFC) systems but thermal stresses induced by the increased temperature gradients may inflict damage to the stack. Therefore the development of adequate control strategies requires models that can accurately predict the temperature profiles in the stack. A 1D dynamic modelling platform is developed in this study and used to simulate SOFCs in both single cell and stack configurations. The single cell model is used to validate power law and Hougen-Watson reforming kinetics derived from experiments in previous work. The stack model based on the same type of cells accounts for heat transfer in the inactive area and to the environment and is validated with data reported by the manufacturer. The reforming kinetics are then implemented in the stack model to simulate operation with direct internal reforming. Although there are differences between the temperature profiles predicted by the two kinetic models both are more realistic than assuming chemical equilibrium. The results highlight the need to identify rate limiting steps for the reforming and hydrogen oxidation reactions on anodes of functional SOFC assemblies. The modelling approach can be used to study off-design conditions transient operation and system integration as well as to develop adequate energy management and control strategies.
Effects of CO2 sequestration on lipid and biomass productivity in microalgal biomass production
Mar 2017
Publication
The study is focused on the technology and manipulation of production strategies for the cultivation of biomass from four strains of microalgae. Species of microalgae studied are: Chlorella vulgaris Dunaliella Scenedesmus quadricauda and Synechococcus spp. The effects of the rate and amount of CO2 removal from the atmosphere and sequestration with dissolved oxygen on lipid production from accumulated biomass were studied. Also the rate of sequestration of both total and dissolved carbon was investigated. Daily measurements of total organic and inorganic carbon sequestrated optical densities proximate analysis and kinetic parameters of the growing and cultivated microalga were monitored and carried out during the two phases of cultivation: dark and light phases. The values of maximum rate of carbon (IV) oxide removed rmax varied from 11.73 mg L -1 min -1 to 18.84 mg L -1 min -1 from Chlorella vulgaris to Synechoccocus spp. Important parameters such as biomass productivity maximum pH values obtained at cultivation lipid content of the produced biomass and the hydraulic detection time for all four strains of microalgae were considered and presented in comparison and with their individual and collective effects. The ratios of the rate of CO2 absorption constant and the constant for the CO2 desorption rate (k1/k2) occurred highest in Dunaliella suggesting that with a high uptake of CO2 the algal strain is more effective in CO2 CO2 sequestration. The best biomass producer in this study was the C. vulgaris (Xmax = 5400 mg L-1 and Px = 35.1 mg L h -1) where biomass productivity is Px and the maximum cellular concentration is Xmax. C. vulgaris has the highest lipids productivity of 27% while Synechoccocus has the least (11.72%). In general biomass productivity may be inversely related; this fact may be explained by greater metabolic involvement of lipid biosynthesis. This pioneer study may be advanced further to developing models for strategic manipulation and optimisation approach in micro algal biomass cultivation.
Electrochemical and Mechanical Stability of Catalyst Layers in Anion Exchange Membrane Water Electrolysis
Dec 2021
Publication
Anion exchange membrane (AEM) water electrolysis is considered a promising solution to future cost reduction of electrochemically produced hydrogen. We present an AEM water electrolyzer with CuCoOx as the anode catalyst and Aemion as membrane and electrode binder. Full cell experiments in pure water and 0.1 M KOH revealed that the optimum binder content depended on the type of electrolyte employed. Online dissolution measurements suggested that Aemion alone was not sufficient to establish an alkaline environment for thermodynamically stabilizing the synthesized CuCoOx in a neutral electrolyte feed. A feed of base is thus indispensable to ensure the thermodynamic stability of such non-noble catalyst materials. Particle loss and delamination of the catalyst layer during MEA operation could be reduced by employing a heat treatment step after electrode fabrication. This work summarizes possible degradation pathways for low-cost anodes in AEMWE and mitigation strategies for enhanced system durability and performance.
High-stability, High-capacity Oxygen Carriers: Iron Oxide-perovskite Composite Materials for Hydrogen Production by Chemical Looping
Jun 2015
Publication
Iron oxide has been widely used as an oxygen carrier material (OCM) for hydrogen production by chemical looping due to its favourable thermodynamic properties. In spite of this iron oxide loses much of its activity after redox cycling mainly due to sintering and agglomeration. Perovskites such as La0.7Sr0.3FeO3-d (LSF731) have been suggested as potential candidate OCMs for hydrogen production due to their excellent oxygen transport properties and stability under cycling. However hydrogen production per cycle for a similar carrier weight is lower than with iron oxide. This work proposes the use of composite OCMs made of iron oxide clusters embedded in an LSF731 matrix. The perovskite matrix facilitates oxygen transport to the iron oxide clusters while preventing agglomeration. Two preparation methods mechanical mixing and a modified Pechini method were used to obtain composite materials with different iron oxide weight fractions 11 and 30 wt.%. The reactivity of these OCMs was studied in a thermogravimetric analyser. Hydrogen production and carrier stability were investigated in a microreactor over 25 redox cycles while periodically feeding carbon monoxide and water in order to produce carbon dioxide and hydrogen in separate streams. Hydrogen production was stable over 25 cycles for LSF731 and the composite OCM with 30 wt.% iron oxide produced by the modified Pechini method but iron oxide particles alone underwent a decrease in the hydrogen production with cycling. The hydrogen production during the 25th cycle was eight times higher for the composite material than for iron oxide alone and four times higher than for LSF731. The hydrogen production was therefore also higher than that expected from a simple combination of the iron oxide and LSF731 alone indicating a synergetic effect whereby the LSF731 may have a higher effective oxygen capacity when in the form of the composite material.
Challenges and Important Considerations When Benchmarking Single-cell Alkaline Electrolyzers
Nov 2021
Publication
This study outlines an approach to identifying the difficulties associated with the bench-marking of alkaline single cells under real electrolyzer conditions. A challenging task in the testing and comparison of different catalysts is obtaining reliable and meaningful benchmarks for these conditions. Negative effects on reproducibility were observed due to the reduction in conditioning time. On the anode side a stable passivation layer of NiO can be formed by annealing of the Ni foams which is even stable during long-term operation. Electrical contact resistance and impedance measurements showed that most of the contact resistance derived from the annealed Ni foam. Additionally analysis of various overvoltages indicated that most of the total overvoltage comes from the anode and cathode activation overpotential. Different morphologies of the substrate material exhibited an influence on the performance of the alkaline single cell based on an increase in the ohmic resistance.
Secure, Affordable, Low Carbon: Gas in our Future Energy System
Feb 2020
Publication
Our gas network is one of the best developed in the world providing safe secure affordable energy to homes and businesses across the UK.<br/><br/>To meet the biggest energy challenge of our generation – making deep cuts to carbon emissions by 2050 – it needs to embrace new technology which builds on these strengths and delivers the integrated flexible network of the future. This briefing sets out how it is already doing that. Take a look at our Gas Futures Messages booklet attached.
Conceptual Design of Pyrolytic Oil Upgrading Process Enhanced by Membrane-Integrated Hydrogen Production System
May 2019
Publication
Hydrotreatment is an efficient method for pyrolytic oil upgrading; however the trade-off between the operational cost on hydrogen consumption and process profit remains the major challenge for the process designs. In this study an integrated process of steam methane reforming and pyrolytic oil hydrotreating with gas separation system was proposed conceptually. The integrated process utilized steam methane reformer to produce raw syngas without further water–gas-shifting; with the aid of a membrane unit the hydrogen concentration in the syngas was adjusted which substituted the water–gas-shift reactor and improved the performance of hydrotreater on both conversion and hydrogen consumption. A simulation framework for unit operations was developed for process designs through which the dissipated flow in the packed-bed reactor along with membrane gas separation unit were modelled and calculated in the commercial process simulator. The evaluation results showed that the proposed process could achieve 63.7% conversion with 2.0 wt% hydrogen consumption; the evaluations of economics showed that the proposed process could achieve 70% higher net profit compared to the conventional plant indicating the potentials of the integrated pyrolytic oil upgrading process.
End of Life of Fuel Cells and Hydrogen Products: From Technologies to Strategies
Feb 2019
Publication
End-of-Life (EoL) technologies and strategies are needed to support the deployment of fuel cells and hydrogen (FCH) products. This article explores current and novel EoL technologies to recover valuable materials from the stacks of proton exchange membrane fuel cells and water electrolysers alkaline water electrolysers and solid oxide fuel cells. Current EoL technologies are mainly based on hydrometallurgical and pyro-hydrometallurgical methods for the recovery of noble metals while novel methods attempt to recover additional materials through efficient safe and cost-competitive pathways. Strengths weaknesses opportunities and threats of the reviewed EoL technologies are identified under techno-economic environmental and regulatory aspects. Beyond technologies strategies for the EoL of FCH stacks are defined mainly based on the role of manufacturers and recovery centres in the short- mid- and long-term. In this regard a dual role manufacturer/recovery centre would characterise long-term scenarios within a potential context of a well-established hydrogen economy.
Energy-efficient Conversion of Microalgae to Hydrogen and Power
Jun 2017
Publication
An integrated system for H2 production from microalgae and its storage is proposed employing enhanced process integration technology (EPI). EPI consists of two core technologies i.e. exergy recovery and process integration. The proposed system includes a supercritical water gasification H2 separation hydrogenation and combined cycle. Microalga Chlorella vulgaris is used as a material for evaluation. The produced syngas is separated to produce highly pure H2. Furthermore to store the produced H2 liquid organic H2 carrier of toluene-and-methylcyclohexane cycle is adopted. The remaining gas is used as fuel for combustion in combined cycle to generate electricity. The effects of fluidization velocity and gasification pressure to energy efficiency are evaluated. From process modelling and calculation it is shown that high total energy efficiency about 60% can be achieved. In addition about 40% of electricity generation efficiency can be realized.
Aqueous Phase Reforming in a Microchannel Reactor: The Effect of Mass Transfer on Hydrogen Selectivity
Aug 2013
Publication
Aqueous phase reforming of sorbitol was carried out in a 1.7 m long 320 mm ID microchannel reactor with a 5 mm Pt-based washcoated catalyst layer combined with nitrogen stripping. The performance of this microchannel reactor is correlated to the mass transfer properties reaction kinetics hydrogen selectivity and product distribution. Mass transfer does not affect the rate of sorbitol consumption which is limited by the kinetics of the reforming reaction. Mass transfer significantly affects the hydrogen selectivity and the product distribution. The rapid consumption of hydrogen in side reactions at the catalyst surface is prevented by a fast mass transfer of hydrogen from the catalyst site to the gas phase in the microchannel reactor. This results in a decrease of the concentration of hydrogen at the catalyst surface which was found to enhance the desired reforming reaction rate at the expense of the undesired hydrogen consuming reactions. Compared to a fixed bed reactor the selectivity to hydrogen in the microchannel reactor was increased by a factor of 2. The yield of side products (mainly C3 and heavier hydrodeoxygenated species) was suppressed while the yield of hydrogen was increased from 1.4 to 4 moles per mole of sorbitol fed.
Hydrogen Production and Subsequent Adsorption/Desorption Process within a Modified Unitized Regenerative Fuel Cell
Apr 2019
Publication
For sustainable and incremental growth mankind is adopting renewable sources of energy along with storage systems. Storing surplus renewable energy in the form of hydrogen is a viable solution to meet continuous energy demands. In this paper the concept of electrochemical hydrogen storage in a solid multi-walled carbon nanotube (MWCNT) electrode integrated in a modified unitized regenerative fuel cell (URFC) is investigated. The method of solid electrode fabrication from MWCNT powder and egg white as an organic binder is disclosed. The electrochemical testing of a modified URFC with an integrated MWCNT-based hydrogen storage electrode is performed and reported. Galvanostatic charging and discharging was carried out and results analyzed to ascertain the electrochemical hydrogen storage capacity of the fabricated electrode. The electrochemical hydrogen storage capacity of the porous MWCNT electrode is found to be 2.47 wt% which is comparable with commercially available AB5-based hydrogen storage canisters. The obtained results prove the technical feasibility of a modified URFC with an integrated MWCNT-based hydrogen storage electrode which is the first of its kind. This is surelya step forward towards building a sustainable energy economy
To Adopt CCU Technology or Not? An Evolutionary Game between Local Governments and Coal-Fired Power Plants
Apr 2022
Publication
Carbon dioxide capture and utilization (CCU) technology is a significant means by which China can achieve its ambitious carbon neutrality goal. It is necessary to explore the behavioral strategies of relevant companies in adopting CCU technology. In this paper an evolutionary game model is established in order to analyze the interaction process and evolution direction of local governments and coal-fired power plants. We develop a replicator dynamic system and analyze the stability of the system under different conditions. Based on numerical simulation we analyze the impact of key parameters on the strategies of stakeholders. The simulation results show that the unit prices of hydrogen and carbon dioxide derivatives have the most significant impact: when the unit price of hydrogen decreases to 15.9 RMB/kg or the unit price of carbon dioxide derivatives increases to 3.4 RMB/kg the evolutionary stabilization strategy of the system changes and power plants shift to adopt CCU technology. The results of this paper suggest that local governments should provide relevant support policies and incentives for CCU technology deployment as well as focusing on the synergistic development of CCU technology and renewable energy hydrogen production technology
Designing Optimal Integrated Electricity Supply Configurations for Renewable hydrogen Generation in Australia
Jun 2021
Publication
The high variability and intermittency of wind and solar farms raise questions of how to operate electrolyzers reliably economically and sustainably using pre-dominantly or exclusively variable renewables. To address these questions we develop a comprehensive cost framework that extends to include factors such as performance degradation efficiency financing rates and indirect costs to assess the economics of 10 MW scale alkaline and proton-exchange membrane electrolyzers to generate hydrogen. Our scenario analysis explores a range of operational configurations considering (i) current and projected wholesale electricity market data from the Australian National Electricity Market (ii) existing so-lar/wind farm generation curves and (iii) electrolyzer capital costs/performance to determine costs of H2production in the near (2020–2040) and long term(2030–2050). Furthermore we analyze dedicated off-grid integrated electro-lyzer plants as an alternate operating scenario suggesting oversizing renewable nameplate capacity with respect to the electrolyzer to enhance operational capacity factors and achieving more economical electrolyzer operation.
Sub-second and Ppm-level Optical Sensing of Hydrogen Using Templated Control of Nano-hydride Geometry and Composition
Apr 2021
Publication
The use of hydrogen as a clean and renewable alternative to fossil fuels requires a suite of flammability mitigating technologies particularly robust sensors for hydrogen leak detection and concentration monitoring. To this end we have developed a class of lightweight optical hydrogen sensors based on a metasurface of Pd nano-patchy particle arrays which fulfills the increasing requirements of a safe hydrogen fuel sensing system with no risk of sparking. The structure of the optical sensor is readily nano-engineered to yield extraordinarily rapid response to hydrogen gas (<3 s at 1 mbar H2) with a high degree of accuracy (<5%). By incorporating 20% Ag Au or Co the sensing performances of the Pd-alloy sensor are significantly enhanced especially for the Pd80Co20 sensor whose optical response time at 1 mbar of H2 is just ~0.85 s while preserving the excellent accuracy (<2.5%) limit of detection (2.5 ppm) and robustness against aging temperature and interfering gases. The superior performance of our sensor places it among the fastest and most sensitive optical hydrogen sensors.
Durability of Anion Exchange Membrane Water Electrolyzers
Apr 2021
Publication
Interest in the low-cost production of clean hydrogen is growing. Anion exchange membrane water electrolyzers (AEMWEs) are considered one of the most promising sustainable hydrogen production technologies because of their ability to split water using platinum group metal-free catalysts less expensive anode flow fields and bipolar plates. Critical to the realization of AEMWEs is understanding the durability-limiting factors that restrict the long-term use of these devices. This article presents both durability-limiting factors and mitigation strategies for AEMWEs under three operation modes i.e. pure water-fed (no liquid electrolyte) concentrated KOH-fed and 1 wt% K2CO3-fed operating at a differential pressure of 100 psi. We examine extended-term behaviors of AEMWEs at the single-cell level and connect their behavior with the electrochemical chemical and mechanical instability of single-cell components. Finally we discuss the pros and cons of AEMWEs under these operation modes and provide direction for long-lasting AEMWEs with highly efficient hydrogen production capabilities.
Artificial Neural Network Based Optimization of a Six-step Two-bed Pressure Swing Adsorption System for Hydrogen Purification
Apr 2021
Publication
The pressure swing adsorption (PSA) system is widely applied to separate and purify hydrogen from gaseous mixtures. The extended Langmuir equation fitted from the extended Langmuir-Freundlich isotherm has been used to predict the adsorption isothermal of hydrogen and methane on the zeolite 5A adsorbent bed. A six-step two-bed PSA model for hydrogen purification is developed and validated by comparing its simulation results with other works. The effects of the adsorption pressure the P/F ratio the adsorption step time and the pressure equalization time on the performance of the hydrogen purification system are studied. A four-step two-bed PSA model is taken into consideration and the six-step PSA system shows higher about 13% hydrogen recovery than the four-step PSA system. The performance of the vacuum pressure swing adsorption (VPSA) system is compared with that of the PSA system the VPSA system shows higher hydrogen purity than the PSA system. Based on the validated PSA model a dataset has been produced to train the artificial neural network (ANN) model. The effects of the number of neurons in the hidden layer and the number of samples used for training ANN model on the predicted performance of ANN model are investigated. Then the well-trained ANN model with 6 neurons in the hidden layer is applied to predict the performance of the PSA system for hydrogen purification. Multi-objective optimization of hydrogen purification system is performed based on the trained ANN model. The artificial neural network can be considered as a very effective method for predicting and optimizing the performance of the PSA system for hydrogen purification.
Experimental and Numerical Study of Low Temperature Methane Steam Reforming for Hydrogen Production
Dec 2017
Publication
Low temperature methane steam reforming for hydrogen production using experimental developed Ni/Al2O3 catalysts is studied both experimentally and numerically. The catalytic activity measurements were performed at a temperature range of 500–700 ◦C with steam to carbon ratio (S/C) of 2 and 3 under atmospheric pressure conditions. A mathematical analysis to evaluate the reaction feasibility at all different conditions that have been applied by using chemical equilibrium with applications (CEA) software and in addition a mathematical model focused on the kinetics and the thermodynamics of the reforming reaction is introduced and applied using a commercial finite element analysis software (COMSOL Multiphysics 5.0). The experimental results were employed to validate the extracted simulation data based on the yields of the produced H2 CO2 and CO at different temperatures. A maximum hydrogen yield of 2.7 mol/mol-CH4 is achieved at 700 ◦C and S/C of 2 and 3. The stability of the 10%Ni/Al2O3 catalyst shows that the catalyst is prone to deactivation as supported by Thermogravimetric Analysis TGA results.
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