Search Results (23)

Green hydrogen production from water electrolysis (WE) is one of the most promising technologies to realize a decarbonized future and efficiently utilize intermittent renewable energy. Among the various WE technologies, the emerging anion exchange membrane (AEMWE) technology shows the greatest potential for producing green hydrogen at a competitive price. To achieve this goal, simple methods for the large-scale synthesis of efficient and low-cost electrocatalysts are needed. This paper proposes a very simple and scalable process for the synthesis of nanostructured NiCo- and NiFe-based electrode materials for a zero-gap AEMWE full cell. For the preparation of the cell anode, oxides with different Ni molar fractions (0.50 or 0.85) are synthesized by the sol–gel method, followed by calcination in air at different temperatures (400 or 800 °C). To fabricate the cell cathode, the oxides are reduced in a H₂/Ar atmosphere. Electrochemical testing reveals that phase purity and average crystal size significantly influence cell performance. Highly pure and finely grained electrocatalysts yield higher current densities at lower overpotentials. The best performing membrane electrode assembly exhibits a current density of 1 A cm⁻² at 2.15 V during a steady-state 150 h long stability test with 1 M KOH recirculating through the cell, the lowest series resistance at any cell potential (1.8 or 2.0 V), and the highest current density at the cut-off voltage (2.2 V) both at the beginning (1 A cm⁻²) and end of tests (1.78 A cm⁻²). The presented results pave the way to obtain, via simple and scalable techniques, cost-effective catalysts for the production of green hydrogen aimed at a wider market penetration by AEMWE. Full article

China has abundant biomass and renewable energy resources suitable for producing green methanol via biomass thermochemical conversion. Given China’s increasing demand for sustainable fuel alternatives and the urgency to reduce carbon emissions, optimizing biomass utilization through gasification is critical. Research has highlighted the potential of integrating biomass gasification with water electrolysis to enhance efficiency in green methanol production, leveraging China’s vast biomass reserves to establish a cleaner energy pathway. Four main biomass gasification technologies—fixed-bed, fluidized-bed, pressurized fluidized-bed, and entrained-flow—have been investigated. Fixed-bed and bubbling fluidized-bed gasification face low gas yield and scaling issues; whereas, circulating fluidized-bed gasification (CFB) offers better gas yield, carbon efficiency, and scalability, though it exhibits high tar and methane in syngas. Pressurized fluidized-bed gasification improves gasification intensity, reaction rate, and equipment footprint, yet stable feedstock delivery under pressure remains challenging. Entrained-flow gasification achieves high carbon conversion and low tar but requires finely crushed biomass, restricted by biomass’ low combustion temperature and fibrous nature. Current industrially promising routes include oxygen-enriched and steam-based CFB gasification with tar cracking, which reduces tar but requires significant energy and investment; oxygen-enriched combustion to produce CO₂ for methanol synthesis, though oxygen in flue gas can poison catalysts; and a new high oxygen equivalence ratio CFB gasification technology proposed here, which lowers tar formation and effectively removes oxygen from syngas, thereby enabling efficient green methanol production. Overcoming feedstock challenges, optimizing operating conditions, and controlling tar and catalyst poisoning remain key hurdles for large-scale commercialization. Full article

Designing and developing highly active, stable, and cost-effective hydrogen evolution reaction (HER) catalysts is crucial in the field of water electrolysis. In this study, we utilize N-doped porous carbon (CoNC) derived from zeolite imidazole metal–organic frameworks (ZIF-67) as support and prepare CoNC-Pt-IM-P via chemical impregnation (CoNC-Pt-IM) and plasma treatment. Systematic analyses reveal that calcined CoNC with pyridinic nitrogen could serve as a robust support to strongly anchor PtCo nanoclusters, while argon plasma treatment could lead to a noticeable aggregation of Co and Pt atoms so as to alter the electronic environment and enhance intrinsic HER catalytic activity. CoNC-Pt-IM-P could exhibit outstanding catalytic activity toward HER, achieving an exceptionally low overpotential of 31 mV at the current density of −10 mA cm⁻² and a Tafel slope of 36 mV dec⁻¹. At an overpotential of 50 mV, its mass activity reaches 4.90 A mg_Pt⁻¹, representing enhancements of 1.5 times compared to CoNC-Pt-IM and 12.3 times compared to commercial 20 wt% Pt/C. Furthermore, it could operate stably for over 110 h at a current density of −10 mA cm⁻², demonstrating its exceptional durability. This work uses plasma treatment to achieve the controllable aggregation of Co and Pt atoms to enhance their catalytic activity, which has the advantage of avoiding excessive particle aggregation compared to the commonly used method of high-temperature calcination. Full article

The conventional Haber–Bosch process (HBP) for NH₃ production results in CO₂ emissions of almost 400 Mt/y and is responsible for 1–2% of global energy consumption; furthermore, HBP requires large-scale industrial equipment. Green or e-ammonia produced with hydrogen from alkaline water electrolysis using renewable energy and nitrogen from the air is considered an alternative to fossil-fuel-based ammonia production. Small-scale plants with the distributed on-site production of e-ammonia will begin to supplant centralized manufacturing in a carbon-neutral framework due to its flexibility and agility. In this study, a flexible small-scale NH₃ plant is analyzed with respect to three steps—H₂ generation, air separation, and NH₃ synthesis—to understand if milder operating conditions can benefit the process. This study investigates the aspects of flexible small-scale NH₃ plants powered by alkaline electrolyzer units with three specific capacities: 1 MW, 5 MW, and 10 MW. The analysis is carried out through Aspen Plus V14 simulations, and the primary criteria for selecting the pressure, temperature, and number of reactors are based on the maximum ammonia conversion and minimum energy consumption. The results show that: (i) the plant can be operated across a wide range of process variables while maintaining low energy consumption and (ii) alkaline electrolysis is responsible for the majority of energy consumption, followed by the ammonia synthesis loop and the obtention of N₂, which is negligible. Full article

Tungsten is a high-value resource with a wide range of applications. The tungsten metal is produced via ammonium paratungstate, which is a multi-stage process including leaching, conversion, precipitation, calcination, and reduction. A short process to produce tungsten metal from the electrolysis of molten sodium tungstate has been demonstrated. However, sodium tungstate cannot be directly produced from wolframite in the conventional hydrometallurgical process. There was no information reported in the literature on producing sodium tungstate directly from tungsten concentrates. The present study proposed a simple and low-cost process to produce sodium tungstate by high-temperature processing of wolframite. The mixtures of wolframite, sodium carbonate, and silica were melted in air between 1100 and 1300 °C. High-density sodium tungstate was easily separated from the immiscible slag, which contained all impurities from wolframite, flux, excess sodium oxide, and dissolved tungsten oxide. The slag was further water leached to recover sodium tungstate in the solution. Effects of Na₂CO₃/Ore and SiO₂/Ore ratios, temperature, and reaction time on the recovery of tungstate and the purity of sodium tungstate were systematically studied. Sodium tungstate containing over 78% WO₃ was produced in the smelting process, which is suitable for the electrolysis process. The experimental results will provide a theoretical basis for the direct production of sodium tungstate from wolframite. The compositions of the WO₃-containing slags and sodium tungstate reported in the present study fill the knowledge gap of the tungsten-containing thermodynamic database. Further studies to use complex and low-grade tungsten concentrates to produce sodium tungstate are underway. Full article

Efforts towards climate neutrality in Europe must prioritise manufacturing industries, particularly the energy-intensive industry (EII) subsectors. This work proposes a novel approach to assessing transformation options for EII subsectors. At the center of this approach we position a potential analysis of technologies’ impact on subsector decarbonisation—an approach only known so far from the investigation of renewable energy potentials. These so-called technical climate neutrality potentials, supplemented by a set of indicators taking into account energy consumption, capital and operational expenditures, and GHG taxation programs per technology and subsector, enable cross-sector comparisons. The indicators allow the reader to compare the impact on GHG emission mitigation, energy demand, and cost for every considered technology. At the same time, we keep an open mind regarding combinations of technological solutions in the overall energy system. This ensures that the technology pathways with the greatest climate neutrality potential are easily identified. These focal points can subsequently serve in, e.g., narrative-driven scenario analyses to define comprehensive guides for action for policymakers. A case study of Austria for the proposed potential analysis demonstrates that bio-CH₄ and electrolysis-derived H₂ are the most economical green gases, but GHG certificate costs will be necessary for cost-competitiveness in high-temperature applications. Electrification offers advantages over conventional technologies and CO₂-neutral gas alternatives in low-to-mid temperature ranges. Under the given assumptions, including GHG emission certificate costs of 250 EUR/t CO₂, alternative technologies in the identified climate neutrality pathways can operate at total annual costs comparable to conventional fossil-based equivalents. Full article

This work investigated hydrogen production from biomass feedstocks (i.e., glucose, starch, lignin and cellulose) using a 100 mL h-type proton exchange membrane electrolysis cell. Biomass electrolysis is a promising process for hydrogen production, although low in technology readiness level, but with a series of recognised advantages: (i) lower-temperature conditions (compared to thermochemical processes), (ii) minimal energy consumption and low-cost post-production, (iii) potential to synthesise high-volume H₂ and (iv) smaller carbon footprint compared to thermochemical processes. A Lewis acid (FeCl₃) was employed as a charge carrier and redox medium to aid in the depolymerisation/oxidation of biomass components. A comprehensive analysis was conducted, measuring the H₂ and CO₂ emission volume and performing electrochemical analysis (i.e., linear sweep voltammetry and chronoamperometry) to better understand the process. For the first time, the influence of temperature on current density and H₂ evolution was studied at temperatures ranging from ambient temperature (i.e., 19 °C) to 80 °C. The highest H₂ volume was 12.1 mL, which was produced by FeCl₃-mediated electrolysis of glucose at ambient temperature, which was up to two times higher than starch, lignin and cellulose at 1.20 V. Of the substrates examined, glucose also showed a maximum power-to-H₂-yield ratio of 30.99 kWh/kg. The results showed that hydrogen can be produced from biomass feedstock at ambient temperature when a Lewis acid (FeCl₃) is employed and with a higher yield rate and a lower electricity consumption compared to water electrolysis. Full article

The oxygen evolution reaction (OER) is a key half-reaction in electrocatalytic water splitting. Large-scale water electrolysis is hampered by commercial noble-metal-based OER electrocatalysts owing to their high cost. To address these issues, we present a facile, one-pot, room-temperature co-precipitation approach to quickly synthesize carbon-nanotube-interconnected amorphous NiFe-layered double hydroxides (NiFe-LDH@CNT) as cost-effective, efficient, and stable OER electrocatalysts. The hybrid catalyst NiFe-LDH@CNT delivered outstanding OER activity with a low onset overpotential of 255 mV and a small Tafel slope of 51.36 mV dec⁻¹, as well as outstanding long-term stability. The high catalytic capability of NiFe-LDH@CNT is associated with the synergistic effects of its room-temperature synthesized amorphous structure, bi-metallic modulation, and conductive CNT skeleton. The room-temperature synthesis can not only offer economic feasibility, but can also allow amorphous NiFe-LDH to be obtained without crystalline boundaries, facilitating long-term stability during the OER process. The bi-metallic nature of NiFe-LDH guarantees a modified electronic structure, providing additional catalytic sites. Simultaneously, the highly conductive CNT network fosters a nanoporous structure, facilitating electron transfer and O₂ release and enriching catalytic sites. This study introduces an innovative approach to purposefully design nanoarchitecture and easily synthesize amorphous transition-metal-based OER catalysts, ensuring their cost effectiveness, production efficiency, and long-term stability. Full article

The current race for space exploration has hastened the development of electrochemical technologies for the in-situ utilisation of planetary resources for the synthesis of vital chemicals such as O₂ and fuels. Understanding the physicochemical properties, such as the density and kinematic viscosity, of aqueous solutions is essential for the design of electrochemical devices for the electrolysis of water and CO₂, particularly at low temperatures. The density and kinematic viscosity of highly concentrated Mg(ClO₄)₂ and KOH solutions have been determined, both at low temperatures and in the presence of CO₂ gas. It was found that, for all of the solutions, independent of the concentration or nature of the electrolyte, as the temperature was decreased to 255 K, the density and the viscosity of the solutions increased. Upon saturation with CO₂, no significant change to the density and viscosity of Mg(ClO₄)₂, at all of the temperatures measured, was observed. Conversely, the CO₂ saturated solutions of KOH showed significant changes in density and viscosity at all temperatures, likely due to the formation of carbonates. The effects of these changes on the diffusion coefficient for dissolved CO₂ is also discussed. Full article

As the global climate crisis escalates, reductions in CO₂ emissions and the efficient utilization of carbon waste resources have become a crucial consensus. Among the various carbon mitigation technologies, the concept of power-to-liquid (PTL) has gained significant attention in recent years. Considering the lack of a timely review of the state-of-the-art progress of this PTL process, this work aims to provide a systematic summary of the advanced PTL progress. In a CO₂ capture unit, we compared the process performances of chemical absorption, physical absorption, pressure swing adsorption, and membrane separation technologies. In a water electrolysis unit, the research progress of alkaline water electrolysis, proton exchange membrane water electrolysis, and solid oxide water electrolysis technologies was summarized, and the strategies for improving the electrolysis efficiency were proposed. In a CO₂ hydrogenation unit, we compared the differences of high-temperature and low-temperature Fischer–Tropsch synthesis processes, and summarized the advanced technologies for promoting the conversion of CO₂ into high value-added hydrocarbons and achieving the efficient utilization of C₁–C₄ hydrocarbons. In addition, we critically reviewed the technical and economic performances of the PTL process. By shedding light on the current state of research and identifying its crucial factors, this work is conducive to enhancing the understanding of the PTL process and providing reliable suggestions for its future industrial application. By offering valuable insights into the PTL process, this work also contributes to paving the way for the development of more efficient and sustainable solutions to address the pressing challenges of CO₂ emissions and climate change. Full article

In this paper, the results of an experimental study on hydrogen production at a tungsten discharge electrode with negative polarity in the DC electrolysis of a typical 10 wt% Na₂CO₃ aqueous solution in three operational regimes (the Faradaic, transition, and plasma-driven solution electrolysis (PDSE)) are presented for the first time. To focus the study on hydrogen production, a flowing inert gas (argon) was used to transport the gas mixture produced at the discharge electrode and prevent any other potential chemical reactions. The results showed that the highest hydrogen production rate of 0.147 g(H₂)/h was achieved in the cathodic PDSE regime at the applied DC voltage of 198 V. However, the energy yield of hydrogen production of 0.405 g(H₂)/kWh obtained at the applied voltage range of 141–170 V in the PDSE regime was lower than that obtained in the Faradaic regime (0.867 g(H₂)/kWh) at 28 V. The energy balance of hydrogen production in the cathodic PDSE regime for the typical aqueous solution of Na₂CO₃ carried out for the first time showed that a significant share (˃98%) of the electrical energy consumed is spent on heating and evaporation of the electrolytic solution. This explains why the energy yield of hydrogen production is low in the PDSE regime. Because most of the energy is consumed for heat generation in the cathodic PDSE regime, organic liquid hydrogen carriers, such as alcohols, which have a lower boiling temperature, heat of evaporation, and standard Gibbs free energy, should be considered better aqueous electrolytic solutions in terms of the energy yield of hydrogen production in the PDSE regime. Full article

Global warming, along with increasing global energy demands, has led to the need for a sustainable and low-carbon-based energy economy. In addition to renewable energy technologies, such as biomass, solar, hydro, and wind, another possible strategy to mitigate climate change is the capture/conversion and recycling of CO₂. In recent years, many methods for both CO₂ capture (mainly adsorption, absorption, and membrane) and conversion (many electrolysis, catalyst, and plasma) have been investigated. Conversion technology is less studied but seems to be very promising. Within that, non-thermal plasma technology has received much interest because it works at low temperatures and atmospheric pressure, and there is no need for high temperature and high electricity consumption, which are typical of the catalyst and electrolysis conversion processes, respectively. Therefore, in order to optimize this emerging technology, simulative kinetic models have been developed with the aim of maximizing both energy efficiency and CO₂ conversion. In the present paper, an overview of the most common non-thermal plasma technologies was carried out to highlight the advantages and disadvantages of each method. Then, an overview of the most significant kinetic models available in literature was carried out to point out the main reactions occurring during CO₂ conversion and also the parameters that most affect the performance of a plasma reactor during CO₂ conversion. Then, a brief recap of the literature available on economic studies of the plasma process is given. Full article

Recently, electro-oxidation of kraft lignin has been reported as a prominent electrochemical reaction to generate hydrogen at lower overpotential in alkaline water electrolysis. However, this reaction is highly limited by the low performance of existing electrocatalysts. Herein, we report a novel yet effective catalyst that comprises nonprecious trimetallic (Ni, Fe, and Co) nanoalloy as a core in a phosphidated nitrogen-doped carbon shell (referred to as sample P-NiFeCo/NC) for efficient electro-oxidation of kraft lignin at different temperatures in alkaline medium. The as-synthesized catalyst electro-oxidizes lignin only at 0.2 V versus Hg/HgO, which is almost three times less positive potential than in the conventional oxygen evolution reaction (0.59 V versus Hg/HgO) at 6.4 mA/cm² in 1 M KOH. The catalyst demonstrates a turnover frequency (TOF) three to five times greater in lignin containing 1 M KOH than that of pure 1 M KOH. More importantly, the catalyst P-NiFeCo/NC shows theoretical hydrogen production of about 0.37 μmoles/min in the presence of lignin, much higher than that in pure 1 M KOH (0.0078 μ moles/min). Thus, this work verifies the benefit of the NiFeCo nanoalloy incorporated in carbon matrix, providing the way to realize a highly active catalyst for the electro-oxidation of kraft lignin. Full article

Decarbonization of the aviation sector is crucial to reaching the global climate targets. We quantified the environmental impacts of Power-to-Liquid kerosene produced via Fischer-Tropsch Synthesis from electricity and carbon dioxide from air as one broadly discussed alternative liquid jet fuel. We applied a life-cycle assessment considering a well-to-wake boundary for five impact categories including climate change and two inventory indicators. Three different electricity production mixes and four different kerosene production pathways in Germany were analyzed, including two Direct Air Capture technologies, and compared to fossil jet fuel. The environmental impacts of Power-to-Liquid kerosene varied significantly across the production pathways. E.g., when electricity from wind power was used, the reduction in CO₂-eq. compared to fossil jet fuel varied between 27.6–46.2% (with non-CO₂ effects) and between 52.6–88.9% (without non-CO₂ effects). The reduction potential regarding CO₂-eq. of the layout using low-temperature electrolysis and high-temperature Direct Air Capture was lower compared to the high-temperature electrolysis and low-temperature Direct Air Capture. Overall, the layout causing the lowest environmental impacts uses high-temperature electrolysis, low-temperature Direct Air Capture and electricity from wind power. This paper showed that PtL-kerosene produced with renewable energy could play an important role in decarbonizing the aviation sector. Full article

Nowadays, transition towards green chemistry is becoming imperative. In this scenario, an attractive perspective consists in the generation of CO through the electrochemical reduction of CO₂ under ambient conditions. This approach allows storage of the electrical energy from intermittent renewable sources in the form of chemical bonds, and simultaneously reduces greenhouse gas emissions, giving carbon a second chance of life. However, most catalysts adopted for this process, i.e., noble metal-based nanoparticles, still have several issues (high costs, low current densities, high overpotentials), and in the view of generating syngas through co-electrolysis of H₂O and CO₂, do not enable a widely tunable CO/H₂ ratio. Single-atom catalysts with N-doped carbon supports have been recently introduced to face these challenges. The following review aims to answer the demand for an extended and exhaustive analysis of the metal single-atom catalysts thus far explored for the electro-reduction of CO₂ in aqueous electrolyte solution. Moreover, focus will be placed on the objective of generating a syngas with a tunable CO/H₂ ratio. Eventually, the advantages of single-atom catalysts over their noble metal-based nano-sized counterparts will be identified along with future perspectives, also in the view of a rapid and feasible scaling-up. Full article