Renewable Hydrogen Production Research Articles

Two birds with one stone: Functionalized wood composites for efficient photocatalytic hydrogen production and solar water evaporation

Maximizing solar energy utilization is a persistent challenge in photo catalysis, which determines sustainable solar-driven photocatalytic process. Photo thermal-coupled photo catalysis is considered as a promising solution to tackle the issues of sustainable energy scarcity and environmental pollution by harvesting the full-spectrum solar energy. Herein, a highly efficient photo thermal-accelerated photo catalysis system is elaborately established, in which the assembled carbonized stick/Nb2C MXene evaporator can heat water into vapor and the integrated g-C3N4 photocatalyst further enables high-efficiency photocatalytic hydrogen production. The designed hyperboloid wood-based architecture possesses a multiphase interface of water steam/catalyst/hydrogen to reduce the transport resistance of hydrogen gas in liquid and ultimately maximize the output of hydrogen energy. Consequently, this coupled photothermal-photocatalytic system achieves a stable solar evaporation rate of 2.16 kg m-1 h-1 under one sun irradiation and highly efficient hydrogen-evolving rate of 3096 µmol g-1 h-1. This work paves a way to explore the improvement of photocatalytic hydrogen production by synergic photothermal effect for potential applications in renewable solar energy utilization and hydrogen production.

(Invited) Hydrogen Consortium: Technical Progress on Renewable Hydrogen Production R&D

HydroGEN Energy Materials Network (EMN) is an U.S. Department of Energy (DOE) EERE Hydrogen and Fuel Cell Technologies Office (HFTO)-funded consortium that aims to accelerate the discovery and development of advanced water splitting materials (AWSM) for clean, low-cost hydrogen production. This is in line with the H2@Scale initiative, with the goal to meet U.S. DOE’s Hydrogen Shot production cost target of $1/kg H2 within 1 decade (1 1 1). Materials innovations are key to enhancing performance, durability, and cost of hydrogen generation technologies. Large scale, low cost hydrogen from diverse domestic resources can enable an economically competitive and environmentally beneficial future energy system across multiple sectors.HydroGEN is focused on low technology readiness level AWS technologies, including low- (alkaline exchanged membrane electrolysis) and high-temperature electrolysis (proton-conducting solid oxide electrolysis), photoelectrochecmical (PEC) and solar thermochemical (STCH) water splitting. This presentation will provide an overview of the HydroGEN EMN and technical highlights of a few lab-led and FOA-awarded R&D projects. HydroGEN continues to grow its community of industry, university, and national laboratories, forming a national innovation ecosystem focused on renewable hydrogen production.

Approaches to Reduce the Operating Temperature of Protonic Ceramic Electrochemical Cells to

Protonic ceramic electrochemical cells (PCECs) have been developed as a promising technology for efficient power generation and hydrogen production via steam electrolysis. However, the current operating temperature range of 450-600°C still limits their widespread application and adoption in ceramic electrochemical cell technology. To address this issue, lowering the operating temperature range to 250-450°C has been proposed, which would expand the range of materials for building PCEC systems and reduce their cost. In this presentation, I will discuss our group's series of approaches to redesign PCECs. These approaches include using readily fabricated single-grain thick, chemically homogeneous, and robust electrolytes, as well as newly developed positive electrode materials. Our innovations have simultaneously reduced the electrolyte ohmic resistance, electrolyte-positive electrode contact resistance, and electrode polarization resistance, while also improving durability. As a result, we have set several new records of using PCECs for both power generation and renewable hydrogen production.

(High-Temperature Energy, Materials, & Processes Division J. B. Wagner, Jr. Young Investigator Award) Protonic Ceramic Electrochemical Cells for Power Generation, Hydrogen Production, and Chemicals Synthesis

Protonic ceramic electrochemical cells (PCECs) show great promise for power generation, renewable hydrogen production, and sustainable chemical synthesis. Our laboratory at Kansas State University has made significant progress in designing PCEC materials, fabricating PCEC devices, and characterizing PCECs for various applications. In this presentation, I will first introduce our novel PCEC materials and fabrication processes, which have enabled reduced operating temperatures, enhanced performance, and improved durability. Then, I will discuss the research and development of three primary applications of PCECs by our group: power generation in fuel cell mode, green hydrogen production in electrolysis mode, and the synthesis of high-value chemicals using abundant feedstocks.

Quantifying Sheet Resistance and in-Plane Electrical Resistivity of PEM Water Electrolyzer Components

PEM water electrolysis is a promising technology for renewable hydrogen production. However, improving the performance and efficiency of PEM water electrolyzers requires a thorough understanding of the properties and behavior of their components. Here we present a robust and effective method for determining the sheet resistance of porous electrodes commonly used in technologies such as PEM water electrolyzers. For this, a new analysis method was developed that relies on industrial printed circuit boards, allowing resistance measurements at ten different length scales ranging from 250 µm to 2500 µm and a 1D mapping of the resistance at each length scale. The sheet resistance of a commercially available reference material is characterized in order to validate the method, and the impact of compression force on the probe-sample contact is demonstrated. Furthermore, the sheet resistance of commonly used PEM water electrolyzer components is investigated. This includes the discussion of the gas diffusion layer, porous transport layer, and catalyst layers coated onto a membrane. Besides, by using an image processing-based method, the thickness distribution of the catalyst layers can be obtained and is correlated with the electrical in-plane resistivity. The results indicate that the sheet resistance is a more relevant parameter than the in-plane electrical resistivity to characterize catalyst layers. We will present a ranking of different PEM water electrolyzer components according to their sheet resistance for both anode and cathode catalyst layers. Acknowledgement This project has received funding from the European Union's Horizon 2020 research and innovation programme under the PROMET-H2 grant agreement No 862253.

Experimental studies on renewable hydrogen production by steam reforming of glycerol over zirconia promoted on Ni/Al2O3 catalyst

Abstract The impact of ZrO2 as a catalytic promoter for nickel-based alumina supported catalysts has been studied for the hydrogen synthesis via glycerol steam reforming. Hydrogen is a promising contender of clean fuel and has a key significance in the quest of an environment-preservation, low emission and more sustainable energy approach. Glycerol is a by-product produced during production of biodiesel by trans-esterification of vegetable oils. The higher hydrogen content in glycerol makes it the potential renewable feedstock for hydrogen production. Steam reforming process is the best method available which is highest in energy efficiency and most importantly most economical. The production of catalysts was based on the wet impregnation and co-precipitation methods. The majority of the bulk and surface properties of different synthesized catalysts were considered and determined by several characterization techniques like X-ray diffraction technique, BET surface area and scanning electron microscopy. The performance of catalyst is based on glycerol conversion and hydrogen yield obtained from the steam reforming process taking place in the fixed bed catalytic reactor. The effect of different operating conditions like contact time, temperature, metal loading, and steam to glycerol ratio were investigated to produce maximum hydrogen and glycerol conversion. The results show that the incorporation of promoter 2 % ZrO2 improved the activity of Ni/Al2O3 catalysts significantly resulting 96 % glycerol conversion, 84 % hydrogen production and greater stability at contact time = 15 kg cat s/mol, temperature = 800 °C, steam to glycerol ratio = 9:1 mol/mol, and pressure = 1 atm.

Structural understanding of IrFe catalyst for renewable hydrogen production from ethanol steam reforming

Ethanol steam reforming (ESR) is an attractive way to produce renewable H2 and has been intensely studied. An iron promoted Ir catalyst IrFe/Al2O3 is reported for the first time to show better performance than Ir/Al2O3 in ESR and the structural change in the IrFe/Al2O3 catalyst under realistic ESR conditions is investigated. IrFe alloy is observed after reduction in H2. However, the IrFe alloy is disrupted during ESR because of an adsorption-induced structural change. Ir appears in metallic-like state while Fe exists as partially reduced FexOy under the reaction condition. The active center is therefore IrFexOy instead of IrFe alloy. The discovery of the transformation of IrFe alloy to IrFexOy during ESR deepens the understanding of the dynamic behaviour of IrFe catalyst and provides a correlation between the catalyst structure and catalytic performance.

High Temperature Solid Oxide Electrolysis – Technology and Modeling

AbstractIn the global quest to renounce from fossil fuels, a large demand for the renewable production of hydrogen via water electrolysis exists. In this context, the solid oxide electrolyzer (SOE) is an interesting technology due to its high efficiency resulting from elevated operating temperatures of up to 900 °C. Physical modeling plays a vital role in the development of SOEs, as it lowers experimental costs and provides insight where measurements reach limits. A main challenge for modeling SOEs is the multitude of physical effects, occurring and interacting on various spatial and temporal scales. This requires assumptions and simplifications, particularly when increasing scope and dimensions of a model. In this review, we discuss the different approaches currently available in literature.

A profitability study for catalytic ammonia production from renewable landfill biogas: Charting a route for the next generation of green ammonia

This study introduces a novel techno-economic approach to renewable ammonia production using landfill biogas. The proposed process involves bio-hydrogen generation from landfill biogas, nitrogen production via air separation, and the Haber-Bosch process. Building on our prior research, which demonstrated the economic competitiveness of renewable hydrogen production from landfill gas, we extend our investigation to analyze the feasibility of producing renewable ammonia from biogas-derived bio-hydrogen. However, the economic analysis for the baseline scenario reveals the current lack of profitability (net present value of −18.3 M€), with ammonia prices needing to quadruple to achieve profitability. Major costs, including investment, maintenance, overhead expenses, and electricity, collectively account for over 70%, suggesting the potential efficacy of investment subsidies as a political tool. Only cases with subsidies exceeding 50% of total investment costs, under current ammonia market prices, would render the green ammonia route profitable. Our findings underscore the significant techno-economic challenges in realizing renewable ammonia production, emphasizing the need for innovation in process engineering and catalytic technologies to enable competitive and scalable green ammonia production.

Optimal design of PV-based grid-connected hydrogen production systems

A cost-optimal design of power-to-hydrogen (PtH) systems is crucial to produce hydrogen at the lowest specific cost. New challenges arise when it comes to ensuring a reliable and cost-effective hydrogen supply in the presence of variable renewable energy sources. In this context, the aim of this analysis is to investigate the optimal design of PV-based grid-connected hydrogen production systems under different scenarios. To this end, an optimisation framework based on the mixed integer linear programming (MILP) technique is developed. Results are presented by employing a set of techno-economic and environmental indicators to provide general guidance on how to optimally size PtH systems, going beyond the analysis of a specific case study. The analysis is applied to Italy and particular attention is paid to exploring the impact of the price of grid electricity.The results indicate that the price of grid electricity strongly affects the optimal design of PtH systems. Specifically, in scenarios with high electricity prices, it is economically convenient to significantly oversize the PV plant and the electrolyser. The optimal PV ratio, representing the ratio between the PV size and the electrolyser size, increases from 1.6 to 2.7 as the electricity price rises from 50 to 300 €/MWh. Additionally, when electricity prices exceed approximately 120 €/MWh, the optimal electrolyser size (in terms of hydrogen production under rated conditions) becomes almost three times larger than the average hydrogen demand. By comparing grid-connected and off-grid scenarios, the importance of the electrical grid is also highlighted: even when poorly used, it plays a crucial role in limiting the size of the hydrogen storage. The levelised cost of hydrogen for the optimal PtH configuration falls within the range of 3.5–7 €/kg (depending on the price of grid electricity) and increases to 8.2 €/kg when the system operates off-grid. Finally, the hydrogen carbon footprint, quantified as kgCO2,e/kgH2, is also explored. Considering the current price and carbon intensity of grid electricity, the cost-optimal PtH configuration already involves the production of renewable hydrogen (<3 kgCO2,e/kgH2).

Coordinated Control Strategy for System of Hydrogen Production from Renewable Energy Considering Regulating Characteristics of Electrolyzers

As a low-carbon and clean form of energy development and utilization, renewable energy hydrogen production technology has received widespread attention. However, under traditional control strategies, the electrolyzers are generally operated at rated power, and their ability to participate in the system of hydrogen production from renewable energy and grid regulation is not fully utilized. Therefore, this article proposes a coordinated control strategy for the system of hydrogen production from renewable energy that considers the regulation characteristics of electrolyzers. Firstly, models of each unit are established, and based on this, the working characteristics of the electrolyzer are analyzed through electrolyzer model simulation. Then, control strategies for each unit were designed, and the additional response control module is added to the control strategy of the electrolyzers to alleviate the fluctuation of DC bus voltage. Finally, through analysis, this coordinated control strategy has been proven to be effective.

Quantification of Methane Emissions Rate Using Landgem Model and Estimating the Hydrogen Production Potential from Municipal Solid Waste Landfill Site

In India, solid waste is deposited mostly in uncontrolled open landfills without proper segregation and handling methods. Organic wastes dumped in a landfill undergo anaerobic decomposition and emit landfill gases like methane and carbon dioxide. Landfill gases are a significant contributor to greenhouse gases and greatly impact climate change. In the interim, reducing gas emissions and controlling and recycling such gasses is important from environmental hygienic, and global perspectives. Landfill gas has tremendous potential to convert as a source of alternative fuel. The present study estimates the CH4 (Methane) and CO2 (Carbon dioxide) emissions and quantifies the renewable energy available and hydrogen production potential using the LandGEM 3.02 empirical models for the Kanuru, Vijayawada landfill. It was observed that methane emission peaked in 2042 with an emission rate according to the model was 2.51E+08 Metric tons CO2 equivalents. The gas-recovery system is an essential component in landfills for extracting energy with 75-80% efficiency; the generation rate of greenhouse gases will reduce to around 1.78E06 Mg of CO2 eq. The predicted methane emissions vary from 1.33E6-9.22E6 cu.m per year for the period of 2010-2042. It was also estimated that annual energy production from LFG emissions was from 1.8-130 GWh per year, and hydrogen production potential was 0.6-43.3 Gg per year. The study concludes that projected scientific data will assist policymakers in creating sustainable MSW management by bridging the gap between sustainable renewable energy production and protecting the environment. The basic objectives of the study include the quantification of landfill gas production using the LandGEM model for Vijayawada, assessing the electricity generation potential of the landfill methane gas emitted, methane and carbon dioxide recovery from landfills with energy conversion could reduce GHG emissions, and estimation of hydrogen generation potential from the landfill methane emissions.

B‐Site‐Metal Exsolution on Perovskite Oxides Activates Alkaline Water Oxidation via the Lattice Oxygen Mechanism

AbstractEffective electrocatalysts are crucial for facilitating the oxygen evolution reaction (OER), the anodic reaction of water electrolysis for renewable green hydrogen production. Perovskite oxides are a group of potential catalysts featuring the lattice oxygen mechanism (LOM) for OER, where O2 formation commences via a lattice oxygen redox process. The LOM pathway breaks the thermodynamic limitation of the adsorbate evolution mechanism (AEM) and achieves a high intrinsic activity. However, perovskite oxides often suffer high OER overpotentials due to the insufficient activation of the LOM pathway. Typically, the overpotential exceeds 300 mV at 10 mA cm−2. This greatly impedes the practical applications of perovskite oxide based OER catalysts. Here, it is demonstrated that the B‐site‐metal exsolution of a La0.6Sr0.4Fe0.8Ni0.2O3‐δ perovskite increases the activity of LOM by a factor of 3.8 at 400 mV overpotential. The activated LOM pathway leads to a 36‐mV reduction in the overpotential at 10 mA cm−2 (from 310 mV to 274 mV) and a 2× increase in the turnover frequency (TOF) at 450 mV overpotential. A membrane electrode assembly (MEA) water electrolyzer equipped with this LSFN‐based catalyst offers 1 A cm−2 current density at 2.46 V and 24‐h operation stability.

Assessment of industrial-scale green hydrogen production using renewable energy

The global pivot towards sustainable energy solutions necessitates a closer examination of green hydrogen production using renewable energy sources. This study aimed to assess the feasibility and efficiency of green hydrogen production on an industrial scale using solar and wind energy in Diyala city, Iraq. Experimental weather data, including solar irradiance, ambient temperature, and wind speed, were meticulously collected throughout 2022. The analysis indicated that, for wind energy, the optimum electrolyser capacity that matched a 1.5 MW wind turbine achieved a hydrogen production of 11,963 kg/year, with associated costs of $8.87/kg. In contrast, when focusing on solar energy, the ideal electrolyser capacity harmonizing with a 2 MW solar photovoltaic generated a notably higher hydrogen output of 94,432 kg/year at a more competitive cost of $6.33/kg. These findings underscore the potential economic advantages of solar-based green hydrogen production over wind-based methods in Diyala city. Furthermore, the significant difference in hydrogen production yields between the two methods emphasizes the need to optimize renewable infrastructure based on location-specific renewable resources. This study offers valuable insights into tailoring green hydrogen production strategies in regions with similar climatic conditions to Diyala and serves as a blueprint for future renewable energy-driven hydrogen production initiatives.

Life cycle assessment of Power-to-Gas (PtG) technology – Evaluation of system configurations of renewable hydrogen and methane production

Power-to-gas (PtG) is a novel technology with many system configurations whose environmental performances require a comparative evaluation with conventional technologies before large-scale deployment. This paper presents a life cycle assessment (LCA) of the PtG concept, assessing the main parameters and system variations involved in producing hydrogen and methane. The global warming potential (GWP) of producing 1 MJ of hydrogen averages 5.1 and 1.2 gCO2eq when electrolyzers are powered by solar PV and wind, respectively. On the other hand, the GWP associated with producing 1 MJ of methane from plant-derived CO2 is 6.5 gCO2eq when electricity is derived from solar PV and 1.5 gCO2eq when wind is utilized as a power source. Except for acidification potential and abiotic depletion, the other characterization factors (e.g., PED, POCP) show a similar pattern as GWP. The well-to-wheel (WTW) carbon footprints per km of hydrogen FCV are 98 % less than diesel ICE, while compressed natural gas vehicles are 29 % less than gasoline ICE.

Sustainable and renewable hydrogen production from recycled aluminum

The whole world has been suffering strong consequences related to climate change. The intense use of fossil fuels in the chemical and automotive industries have put the environment in jeopardy. Thus, the industry has achieved a point of no return and it is urgent the development of renewable and sustainable technologies. Hydrogen has been pointed as a key component of the new era in industry since it can be produced in a clean and sustainable way. Currently the development of hydrogen fuel cells technology has put the automotive sector ahead of the chemical industries in relation to studies regarding the hydrogen production. Chemical industries produce hydrogen with technologies reliant on fossil fuels while the automotive sector has been looking for renewable forms of hydrogen generation. Trains powered by hydrogen fuel cells are a reality in Europe, for instance. Hydrogen generation technological advances must match the pace of the development of fuel cells electrical vehicles in order to the environmental goals and widespread application of fuel cell systems to be achieved. The present study addresses the hydrogen generation from the spontaneous reaction between aluminum and aqueous solution of sodium hydroxide. Aluminum is a metal that presents high exergetic value and can be recycled several times without losing its thermo-mechanical properties. That makes the use of aluminum especially appealing. It will make hydrogen generation a cleaner and more affordable process. Our findings demonstrate that it is possible to predict the kinetic behavior of the reaction using data obtained by the conductometric method. Graphs of electrical conductivity vs time show that is possible to verify the order of the reaction. We will present concepts of kinetic, thermodynamic and transport phenomena of the reaction between solid recycled aluminum and sodium hydroxide in an aqueous solution. The knowledge acquired throughout this study will contribute to the development of a new reactor and as a consequence, a new renewable and sustainable industrial system of hydrogen generation.

Valorization of olive mill wastewater via autothermal reforming for hydrogen production

Olive mill wastewater (OMW) is an effluent of the olive oil industry that is extremely pollutant. Current solutions are either costly or inefficient. In this study, autothermal reforming (ATR) is presented, for the first time, as a solution to this problem, capable of high organic load removal, renewable hydrogen production and thermally neutral operation. The tests were conducted with a ruthenium-nickel catalyst, doped with La2O3, on a SiO2 support. Different operating conditions were tested (T = 400–700 °C and O2/C = 0.0–0.5 mol O2.mol C−1) and a comparison with traditional reforming (TR) was provided. Characterisation of the catalyst was conducted through temperature-programmed oxidation and inductively coupled plasma - optical emission spectroscopy. The catalytic tests showed hydrogen yields – up to 66.8 % for TR and 52.0 % for ATR – with high rates of organic pollutant load removal (always above 98 %, as inferred from the total organic carbon analyses). Furthermore, an energy balance revealed that ATR releases high amounts of energy, up to 272 kJ·molOMW−1, whilst TR has high energy demand, of up to 360 kJ·molOMW−1. In terms of the amount of heat released during the reaction and the net calorific value of the hydrogen produced, it was found that the ATR at 500 °C with O2/C = 0.25 had the best performance, with a total output of 1695 kJ·molOMW−1.

Hard X-ray photoelectron spectroscopy reveals self-organized structures of electrocatalytic nickel oxy-hydroxides

Alkaline water electrolysis represents one of the simplest methods employed for renewable hydrogen production, reaching high conversion efficiency utilizing cheap and abundant transition metals such as nickel and its alloys. The outstanding properties of Ni-materials do not arise from the metallic host, rather from the surface passivated with various oxidized compounds formed during the electrochemical process. This newly formed layer is responsible for the catalytic properties of the system, therefore the investigation of its evolution as function of potential and time is crucial for a deeper understanding of the overall electrochemical process. However, the characterization of the chemical environment at the topmost layer, as well as the underlying layers, is complex and requires surface sensitive techniques. Here, we show that while ambient pressure soft X-ray photoelectron spectroscopy (APXPS) allows to follow the changes of the topmost layer, characterization of the deeper layers modifications occurring during electrocatalysis requires a combination of soft- and hard X-ray photoelectron spectroscopy (XPS/HAXPES), coupled with electrochemical impedance spectroscopy (EIS). The findings show how the high electrocatalytic activity of Ni (oxy)-hydroxides is directly related to the increasing water intercalation into the passivation layer, which supports the long-debated hypothesis of a water mediated OH− diffusion mechanism. High performance of the electrode is promoted by the peculiar structure of the surface, which self-organizes during the initial formation of the passivation layer enabling self-healing during electro-catalysis. Ultimately, we show how the investigation at different depths by means of XPS/HAXPES in combination with EIS allows a better understanding of the chemical changes occurring throughout the passivation layer, signaling a paradigm shift from the traditional explanation of electro-catalysis by a simple electrode material with a stable nanostructure, to a concept leaning towards a dynamic electrochemical interface.

Biofuels and Electrofuels as Alternative Green Fuels for Marine Applications: A Review

Abstract The International Maritime Organization (IMO) has imposed strict regulations to limit marine emissions because the maritime sector is expanding around the world, producing large amounts of emissions that are harmful to the atmosphere. Green alternative fuels, such as biofuels derived from biomass and electrofuels derived from syngas sources, play critical roles in meeting IMO requirements for clean energy with zero emissions. This study presents a brief review of two types of green fuels: 1) the production of biofuels from biomass sources by using various methods, such as the gasification process and the pyrolysis process, as well as the effectiveness of adding a variety of catalysts, and 2) electrofuels as a new method to oppose global warming by employing various carbon capture strategies and renewable hydrogen production based on water electrolysis. Following that, the significant effect of using these green fuels in marine applications is discussed. Overall, the primary goal of this article is to provide data for researchers and industrialists interested in biofuels and electrofuels as promising alternatives to fossil fuels. A large portion of the existing literature published in highly regarded journals, including the most recently published reports, is analyzed.

Renewable Hydrogen Production by Aqueous Phase Reforming of Pure/Refined Crude Glycerol over Ni/Al-Ca Catalysts.

Renewable hydrogen production by aqueous phase reforming (APR) over Ni/Al-Ca catalysts was studied using pure or refined crude glycerol as feedstock. The APR was carried out in a fixed bed reactor at 238 °C, 37 absolute bar for 3 h, using a solution of 5 wt.% of glycerol, obtaining gas and liquid products. The catalysts were prepared by the co-precipitation method, calcined at different temperatures, and characterized before and after their use by several techniques (XRD, ICP-OES, H2-TPR, NH3-TPD, CO2-TPD, FESEM, and N2-physisorption). Increasing the calcination temperature and adding Ca decreased the surface area from 256 to 188 m2/g, and its value after the APR changed depending on the feedstock used. The properties of the acid and basic sites of the catalysts influenced the H2 yield also depending on the feed used. The Ni crystallite was between 6 and 20 nm. In general, the incorporation of Ca into Ni-based catalysts and the increase of the calcination temperature improved H2 production, obtaining 188 mg H2/mol C fed during the APR of refined crude glycerol over Ni/AlCa-675 catalyst, which was calcined at 675 °C. This is a promising result from the point of view of enhancing the economic viability of biodiesel.