Category: Publications

Agneev Mukherjee, Pieterjan Debergh, Metin Bulut, Miet Van Dael, Roel Degens, Giuseppe Cardellini (VITO), Peter Moser, Knut Stahl (RWE)

Download here: https://eco2fuel-project.eu/wp-content/uploads/2025/08/EU-Regulatory-compliance-report-on-efuels.pdf

Summary

Renewable Fuels of Non-Biological Origin (RFNBOs), defined in European Union (EU) legislation as ‘liquid and gaseous fuels whose energy content is derived from renewable sources, excluding biomass’, are a central part of the EU’s decarbonisation strategies. However, the regulatory scenario with respect to RFNBO production and use in the EU is intricate, and different items of the ‘Fit for 55’ package must be considered to get a holistic picture of the prevailing legislative incentives and hurdles. 

The most relevant item of the Fit for 55 package is the revised Renewable Energy Directive (RED III). RED III imposes a RFNBO-specific sub-target on the EU transport sector, with at least 1% of its energy consumption required to come from RFNBOs by 2030. Additionally, RED III also allows the energy provided by RFNBOs to count double towards renewable energy targets, so as to increase the attractiveness of these fuels which are typically more expensive than fossil fuels. RFNBO deployment also receives support from other parts of ‘Fit for 55’. The ReFuelEU aviation initiative, for example, requires 1.2% of aviation fuels in the EU to be synthetic fuels by 2030, rising to 35% in 2050, while the FuelEU maritime regulation, like RED III, allows for RFNBOs to be double counted. 

While RFNBOs can in theory be produced by numerous routes, nearly all present-day production relies on hydrogen production via electrolysis. Other methods such as the electrochemical reduction of carbon dioxide are however under development. The EU has outlined criteria that a fuel must fulfil in order to qualify as a RFNBO. One important criterion is that RFNBOs must only be produced using ‘additional’ renewable electricity, as opposed to replacing existing renewable electricity use. Another is that RFNBOs must achieve a GHG reduction of at least 70% compared to fossil fuels. 

This latter criterion is not very difficult to achieve by most electrolysis or thermocatalytic processes, as the renewable energy used to make the RFNBO is assumed to have zero emissions. However, the CO2 source used to make carbon-containing RFNBOs is an important consideration here. Under RED III, captured emissions from combustion of non-sustainable fuels for electricity production will be considered ‘avoided emissions’ only up to 2035, with emissions from other uses of non-sustainable fuels considered avoided emissions up to 2040. It is very difficult to meet the GHG reduction threshold without subtracting these ’avoided emissions’ from the RFNBO GHG emissions, effectively meaning that RFNBOs after these dates must be made using direct air capture (DAC) or biogenic carbon. These carbon sources are typically more expensive than the inadmissible ‘point’ sources such as cement or steel plants, which is likely to further raise RFNBO prices. 

The absence of a grandfathering clause in RED III, combined with the 20 year-plus amortisation period required for new e-fuel plants, will make any upcoming RFNBO plant based on fossil CO2 sources infeasible. Another potential ramification might be the favouring of non-carbonaceous RFNBOs like hydrogen and ammonia by producers and users as these are unaffected by this clause. 

Sabrina C. Zignani, Alessandra Carbone, Angela Salanitro, Mariarosaria Pascale, Vitaliano Chiodo, Susanna Maisano, Natale Mondello, Giovanni Frisone, Giuseppe Monforte, Antonino S. Aricò (CNR-ITAE), Luca Riillo, Anna Ramunni (DE NORA), Tim De Serrano (BEKAERT), Charly Azra, Ervintal Gutelmacher (HYDROLITE), Joost Helse, Jing Shen, Swapnil Verhade (VITO)

Download here: https://eco2fuel-project.eu/wp-content/uploads/2025/08/Large-scale-low-temperature-electrochemical-CO2-conversion-to-sustainable-fuels.pdf

Abstract

The D5.3 deliverable report of ECO2Fuel deals with the development of membrane-electrodes assemblies (MEAs) with enhanced performance and stability for electrolysis of CO2 to form carbonaceous fuels. An intermediate goal of the project was to select the most promising MEA configuration according to the achieved results in terms of electrochemical performance, stability and faradaic efficiency. 

The down-selected electrocatalysts were a NiFe-layered double hydroxide (LDH) anode developed by CNR and a CuOx cathode developed by UPV. Both catalysts were scaled-up by Monolithos. Promising electrochemical activity and stability were achieved for low temperature CO2 electrolysis by combining these electro-catalysts with a Hydrolite Anion exchange membrane (AEM). Specifically, the Hydrolite GEN 2 AEM developed in the project favorably compared to benchmark membranes. For the electrodes, a catalyst coated substrate configuration was selected by De Nora and a cold assembling procedure was adopted at CNR and VITO to form membrane-electrode assemblies. Ni densified top layer from Bekaert was used for the anode and a hydrophobic carbonaceous diffusion layer for the cathode. The latter was selected to suppress hydrogen evolution reaction (HER) and enhance formation of carbonaceous products. The results were approaching the project objectives for the faradaic efficiency of carbonaceous fuels and voltage efficiency as well as for the stability. Accordingly, the ECO2Fuel cell concept for low-temperature co-electrolysis of CO2 and water forming both gas and liquid carbonaceous fuels was demonstrated at the single cell level. A significant issue related to the clogging of the cathode pores in durability tests was mitigated by specific technical solutions. A long term durability test exceeding 800 hours was carried out and the cathode outlet stream composition was determined by gas chromatography. The developed electrocatalysts were compared to benchmarks showing enhanced activity. 

Manuel Molina-Muriel, Sabrina Campagna Zignani, Sara Goberna-Ferrón, Antonio Ribera, Antonino Salvatore Aricò, Hermenegildo García

Available at: https://pubs.acs.org/doi/10.1021/acsomega.4c11115

Abstract

The growing concern over climate change and the reliance on fossil fuels has spurred interest in alternative energy processes, particularly electrochemical water splitting to produce hydrogen (H₂). This study focuses on developing cost-effective and efficient oxygen evolution reaction (OER) electrocatalysts. We report a novel solvent-free mechanochemical method for synthesizing NiFe-layered double hydroxide (LDH), which demonstrates promising electrocatalytic properties for the OER. The mechanochemical synthesis, requiring only 1 h of solid reagent grinding, produces NiFe-LDH with structural features comparable to those obtained via traditional aqueous phase methods. The electrocatalyst was evaluated in a single cell with a membrane-electrode assembly configuration under alkaline conditions, exhibiting an overpotential of 221 mV at a current density of 10 mA·cm^–2 and a Tafel slope of 103.1 mV·dec^–1, indicating excellent OER kinetics and low energy barriers. Additionally, the catalyst demonstrated robust durability, maintaining a potential of around 1.55 V during a 35 h test at high current densities of 0.1 A·cm^–2 and even 1.75 V at 1 A·cm^–2. This work highlights the potential of NiFe-LDH synthesized by an energy-efficient, environmentally green, and scalable process for large industrial water-splitting applications, contributing to the advancement of sustainable hydrogen production technologies.

Sabrina Campagna Zignani, Alessandra Carbone, Vitaliano Chiodo, Susanna Maisano, Mariarosaria Pascale, Marta Fazio, Luca Riillo, Anna Ramunni, Charly Azra, Ervin Tal Gutelmacher, Antonino Salvatore Aricò

Available at https://doi.org/10.1016/j.cej.2025.163798

Abstract

Low temperature CO₂ − water co-electrolysis was studied in a zero-gap cell based on an anion exchange membrane to produce synthetic fuels at suitable energy efficiency and current density thanks to a proper combination of specific materials, cell configuration and operating conditions. The electrochemical cell consisted of gas-diffusion electrodes containing non-precious electrocatalysts such as nanosized particles-based copper oxide for the cathode and Ni-Fe oxide-hydroxide for the anode. The stability of these electrocatalysts was favoured by a high internal operating pH assured through the recirculation of KOH at the anode. The CO₂ stream was humidified at the operating cell temperature or higher before being fed to the cathode. The process was studied in terms of outlet stream composition, electrochemical performance, faradaic and voltage efficiency through galvanostatic operation at practical current densities, e.g. 0.3 A cm⁻², combined to gas chromatographic analysis. Electrochemical diagnostics, such as polarization curves and ac-impedance spectroscopy combined to productivity data, allowed to derive an interpretation of the cell behaviour under different operating conditions revealing a paramount effect of the ionomer dispersion, added to the cathode, and the operating current density. A useful strategy was adopted to mitigate the precipitation of carbonates. Promising results were observed in terms of production of ethylene and syngas at suitable voltage and faradaic efficiencies. A possible reaction mechanism for the CO₂ reduction under alkaline conditions was considered in relation to the formed products.

Swapnil Varhade, Avni Guruji, Chandani Singh, Giancarlo Cicero, Max García-Melchor, Joost Helsen, Deepak Pant

First published: 12 December 2024

Available at https://doi.org/10.1002/celc.202400512

Abstract

Sustainability is an imperative requirement in this era, with electrocatalytic power into fuels technologies emerging as a significant route toward sustainable chemistry. One of the focus areas within the chemical industry is capture of carbon dioxide (CO₂) and its electrochemical reduction (eCO₂RR) into economically viable commodities through the utilization of renewable sources. Despite some specific eCO₂RR technologies being poised for market introduction, the development of a comprehensive technology for eCO₂RR remains a challenge. While certain technologies targeting specific eCO₂RR products are on the verge of deployment, substantial efforts are still necessary to transition and establish presence in the market over conventional technologies. This review highlights recent technological advancements, fundamental studies, and the persisting challenges from an industrial perspective. We take a deep dive into the research methodologies, strategies, challenges, and advancements in the development of applications for eCO₂RR. Specifically, three eCO₂RR products – CO, HCOOH, and C₂H₄ – as promising candidates for implementation are elaborated based on techno-economic considerations. Additionally, the review discusses the industrial blueprint for these products, aiming to streamline their path toward commercialization. The intent is to present the status of eCO₂RR, offering insights into its potential transformation from a mere laboratory curiosity to a feasible technology for industrial chemical synthesis.

Harilal, Yi-Lin Kao, Chao Pan, David Aili, Qingfeng Li
Available at: https://doi.org/10.1016/j.ssi.2024.116747

Abstract

Water and CO₂ electrolysis at elevated temperatures in cells equipped with short-side-chain perfluorosulfonic acid membranes could potentially allow for new approaches to tuning catalyst kinetics and selectivity, but the membrane characteristics under such conditions remains to be described. In this work, a short-side-chain perfluorosulfonic acid membrane (Aquivion) is characterized at temperatures up to 150 °C and high humidification levels with respect to tensile behavior, ionic conductivity, permeability of hydrogen and methanol, and stability. The membrane is found to retain mechanical robustness at temperatures up to at least 130 °C while dehydration at temperatures above 100 °C under ambient pressure results in a significant conductivity decay. The densification of the membrane matrix at temperatures above the boiling point of water under varied pressures leads to reduced hydrogen and methanol permeability. Pressurization up to 5 bars effectively mitigates the conductivity decay due to the presence of liquid water but also results in increased permeability. The membrane stability test, as characterized by hydrogen crossover measurements, shows that humidification is a harsher stressor than temperature in the studied range.

Moser, Peter and Stahl, Knut and Wiechers, Georg, Closing the Carbon Cycle – Demonstrating Back-Up Power Production from E-Fuels in Gensets and Recycling of the Engine Exhaust Gas (September 26, 2024). Available at SSRN: https://ssrn.com/abstract=5016150 or http://dx.doi.org/10.2139/ssrn.5016150

Abstract

For the first time the concept of back-up power production by combustion of a fuel blend using e-Fuels in a stationary engine (electric output 200 kW) and feeding back the exhaust gas of the engine upstream of an amine-based CO2 capture plant (capture capacity 7.2 t/day CO2 at a capture rate of 90%) was demonstrated at RWE’s Innovation Center at Niederaussem, Germany. The captured CO2 will be later the feedstock for the large 1 MW ECO2Fuel demonstrator to produce carbonaceous e-Fuels, which can again be used in the engine genset, closing the carbon loop. As the exhaust gas has an attractive high temperature level of >400°C that is typically for combined heat and power applications also the potential of the heat reuse and efficiency enhancement was investigated. The analysis and evaluation comprised especially the effect of the changes in the flue gas composition by the exhaust gas recycling (increased O2 and reduced CO2 concentration) on the capture plant performance (specific heat demand for the solvent regeneration, emissions; solvent CESAR1) and the potential of the set-up for combined heat and power applications.

Researchers Sabrina C. Zignani and Antonino S. Aricò have made significant strides in the field of renewable energy with their latest study on CO₂ conversion to synthetic fuels. Utilizing a flow cell reactor with copper and silver-based cathodes, they demonstrate improved selectivity and efficiency in converting carbon dioxide into valuable chemicals, including ethylene, ethanol, and propanol. This innovative approach holds promise for sustainable fuel production, contributing to efforts in reducing atmospheric CO₂ and combating climate change. 

Abstract

As a result of electrochemical conversion of carbon dioxide (CO₂), value-added chemicals like as synthetic fuels and chemical feedstocks can be produced. In the current state of the art, copper-based materials are most widely used being the most effective catalysts for this reaction. It is still necessary to improve the reaction rate and product selectivity of CuOx for electrochemical CO₂ reduction reaction (CO₂RR). The main objective of this work was synthesized and evaluate the copper oxide electrocatalyst combined with silver (CuO 70% Ag 30%) for the conversion of carbon dioxide into synthetic fuels. The catalysts have been prepared by the oxalate method and assessed in a flow cell system. The results of electrochemical experiments were carried out at room temperature and at different potentials (-1.05 V–0.75 V vs. RHE in presence of 0.1 M KHCO₃) and gas and liquid chromatographic analysis are summarized. The CuOx-based electrodes demonstrated the selective of ~ 25% at -0.55 V for formic acid (HCOOH) and over CuO -Ag and selective of ethylene at ~ 20% over CuOx at -1.05 V. Other products were formed as ethylene, ethanol, and propanol (C₂H₄, EtOH, PrOH) at more positive potentials. On the other hand, carbon monoxide, acetate, ethylene glycol, propinaldehyde, glycoaldehyde and glyoxal (CO, CH₃COO, C₂H₆O₂, C₃H₆O, C₂H₄O₂, C₂H₂O₂) have been formed and detected. Based on the results of these studies, it appears that the formation of synthetic fuels from CO₂ at room temperature in alkaline environment can be very promising.

For more detailed insights, read the full study here.