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Renewable Fuels and Chemicals

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A: Sustainable Energy".

Deadline for manuscript submissions: closed (20 May 2025) | Viewed by 1764

Special Issue Editors


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Guest Editor
Department of Chemical and Petroleum Engineering, College of Engineering, Sultan Qaboos University, P.O. Box 33, Al Khould, Muscat 123, Oman
Interests: energy production and conversion, including renewable energy, green hydrogen, green ammonia, hydrogen storage, and enhanced oil recovery; CO2 capture and utilization; process optimization and modeling for higher energy efficiency and enhanced production capacity; wastewater treatment

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Guest Editor
Nanotechnology Research Centre, Sultan Qaboos University, P.O. Box 17, Al-Khoud 123, Oman
Interests: molecular and heterogenous catalysts for small-molecule activation for energy applications, including OER, ORR, HER, NRR, and CO2RR
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The pursuit of sustainable energy solutions is pushing renewable fuels and chemicals to the forefront of scientific innovation. As we anticipate an approximately 50% increase in energy demand by 2050, it becomes crucial for the scientific community to lead the charge in developing renewable energy alternatives. This urgency is compounded by the pressing need to address the harmful environmental impacts of fossil fuel use. Indeed, the move toward renewable energy sources is not just critical for combating climate change but also pivotal in decreasing our dependence on depleting non-renewable resources. Renewable fuels and eco-friendly chemicals serve as key solutions, offering cleaner energy and less carbon emissions, along with new chances for economic growth in innovative industries. Therefore, this Special Issue aims to cover a broad spectrum of topics that are integral to the evolution of the renewable energy and chemical sectors.

Topics of interest for publication include, but are not limited to:

  • Catalysis in renewable fuel/chemical synthesis;
    • Novel catalysts and cell designs for efficient biomass conversion, water splitting, fuel cells, microbial electrolysis cells, CO2 fixation, nitrogen reduction reaction, urea production, etc., and catalyst recovery and recycling methods;
  • Solar fuels;
    • Photochemical and photobiological methods for fuel production, such as artificial photosynthesis;
  • Biomass conversion and valorization;
  • Biogas upgrading and utilization;
  • Green solvents;
  • Carbon capture and utilization (CCU);
  • Use of ionic liquids and supercritical fluids in biofuel extraction and refinement;
  • Chemical storage of renewable energy;
  • Advanced biofuels;
  • Renewable energy integration;
  • Energy economics and policy;
  • Techno-economic analysis of renewable fuels/chemicals;
  • Sustainable fuel utilization.

Dr. Rashid Al-Hajri
Dr. Hussein A. Younus
Guest Editors

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Keywords

  • renewable fuels
  • biofuel production
  • biomass conversion
  • sustainable energy
  • green chemistry
  • catalysis
  • fuel cells
  • CO2 fixation
  • hydrogen energy
  • microbial electrolysis cells
  • energy storage
  • nitrogen reduction
  • urea synthesis
  • catalyst recycling

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Published Papers (3 papers)

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Research

22 pages, 12626 KiB  
Article
Comparative Studies of Three-Dimensional Complex Flow Field Designs in a Proton Exchange Membrane Hydrogen Fuel Cell
by Dilyan Gavrailov and Silviya Boycheva
Energies 2025, 18(9), 2165; https://doi.org/10.3390/en18092165 - 23 Apr 2025
Viewed by 274
Abstract
The performance and durability of proton-exchange membrane fuel cells (PEMFCs) are dependent on fuel flow, humidifying water, and outgoing water management. Unlike conventional flow fields with linear channels, the complex 3D flow field—featuring repeating baffles along the channel, known as the baffle design—induces [...] Read more.
The performance and durability of proton-exchange membrane fuel cells (PEMFCs) are dependent on fuel flow, humidifying water, and outgoing water management. Unlike conventional flow fields with linear channels, the complex 3D flow field—featuring repeating baffles along the channel, known as the baffle design—induces a micro-scale interface flux between the gas diffusion layer (GDL) and the flow fields. Thus, an intensive oxygen flow is created that removes excess water from the GDL, thereby improving the fuel cell efficiency. Another approach for channel design is the Turing flow field, which resembles the organization of fluid flows in natural objects such as leaves, lungs, and the blood system. This design enhances the distribution of inlet flow significantly compared with traditional designs. The present study aims to combine the advantages of both Turing and baffle flow field designs and to provide model investigations on the influence of the mixed flow field design on the efficiency of PEMFCs. It was established that the mixed design achieves the highest electrode current density of 1.2 A/cm2, outperforming the other designs. Specifically, it achieves 20% improvement over the Turing design, reaching 1.0 A/cm2 and generating three times more current than the baffle design, which delivers 0.4 A/cm2. In contrast, the conventional serpentine designs exhibit the lowest current density. The mixed flow field design provides better oxygen utilization in the electrochemical reaction, offers optimal membrane hydration, and contributes to superior electrode current density performance. These data illustrate how flow field structure directly impacts fuel cell efficiency through enhancement of current density. Full article
(This article belongs to the Special Issue Renewable Fuels and Chemicals)
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22 pages, 13573 KiB  
Article
Carbon Capture Adsorbents Based on Ash Residues from the Combustion of Coal with Biomass Blended Fuels
by Silviya Boycheva, Boian Mladenov, Ana Borissova, Momtchil Dimitrov, Ivalina Trendafilova, Daniela Kovacheva and Margarita Popova
Energies 2025, 18(7), 1846; https://doi.org/10.3390/en18071846 - 6 Apr 2025
Viewed by 383
Abstract
One of the approaches to limit the negative impact on the environment from the burning of coal in the production of heat and electricity is to limit their use by blending them with biomass. Blended fuel combustion leads to the generation of a [...] Read more.
One of the approaches to limit the negative impact on the environment from the burning of coal in the production of heat and electricity is to limit their use by blending them with biomass. Blended fuel combustion leads to the generation of a solid ash residue differing in composition from coal ash, and opportunities for its utilization have not yet been studied. The present paper provides results on the carbon capture potential of adsorbents developed through the alkaline conversion of ash mixtures from the combustion of lignite and biomass from agricultural plants and wood. The raw materials and the obtained adsorbents were studied with respect to the following: their chemical and phase composition based on Atomic Absorption Spectroscopy with Inductively Coupled Plasma (AAS-ICP) and X-ray powder diffraction (XRD), respectively, morphology based on scanning electron spectroscopy (SEM), thermal properties based on thermal analysis (TG and DTG), surface parameters based on N2 physisorption, and the type of metal oxides within the adsorbents based on temperature-programmed reduction (TPR) and UV-VIS spectroscopy. The adsorption capacity toward CO2 was studied in dynamic conditions and the obtained results were compared to those of zeolite-like CO2 adsorbents developed through the utilization of the raw coal ash. It was observed that the adsorbents based on ash of blended fuel have a comparable carbon capture potential with coal fly ash zeolites despite their lower specific surface areas due to their compositional specifics and that they could be successfully applied as adsorbents in post-combustion carbon capture systems. Full article
(This article belongs to the Special Issue Renewable Fuels and Chemicals)
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20 pages, 4522 KiB  
Article
Hierarchical Core-Shell Cu@Cu-Ni-Co Alloy Electrocatalyst for Efficient Hydrogen Evolution in Alkaline Media
by Hussein A. Younus, Maimouna Al Hinai, Mohammed Al Abri and Rashid Al-Hajri
Energies 2025, 18(6), 1515; https://doi.org/10.3390/en18061515 - 19 Mar 2025
Viewed by 599
Abstract
The development of advanced electrocatalysts plays a pivotal role in enhancing hydrogen production through water electrolysis. In this study, we employed a two-step electrodeposition method to fabricate a 3D porous Cu-Co-Ni alloy with superior catalytic properties and long-term stability for hydrogen evolution reaction [...] Read more.
The development of advanced electrocatalysts plays a pivotal role in enhancing hydrogen production through water electrolysis. In this study, we employed a two-step electrodeposition method to fabricate a 3D porous Cu-Co-Ni alloy with superior catalytic properties and long-term stability for hydrogen evolution reaction (HER). The resulting trimetallic alloy, Cu@Cu-Ni-Co, demonstrated significant improvements in structural integrity and catalytic performance. A comparative analysis of electrocatalysts, including Cu, Cu@Ni-Co, and Cu@Cu-Ni-Co, revealed that Cu@Cu-Ni-Co achieved the best results in alkaline media. Electrochemical tests conducted in 1.0 M NaOH showed that Cu@Cu-Ni-Co reached a current density of 10 mA cm−2 at a low overpotential of 125 mV, along with a low Tafel slope of 79.1 mV dec−1. The catalyst showed exceptional durability, retaining ~95% of its initial current density after 120 h of continuous operation at high current densities. Structural analysis confirmed that the enhanced catalytic performance arises from the synergistic interaction between Cu, Ni, and Co within the well-integrated trimetallic framework. This integration results in a large electrochemical active surface area (ECSA) of 380 cm2 and a low charge transfer resistance (15.76 Ω), facilitating efficient electron transfer and promoting superior HER activity. These findings position Cu@Cu-Ni-Co as a highly efficient and stable electrocatalyst for alkaline HER in alkaline conditions. Full article
(This article belongs to the Special Issue Renewable Fuels and Chemicals)
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