Research Repository

Welcome to the Research Repository of the μ-FECat Lab! This space serves as a curated collection of our research, offering access to published papers, conference presentations, and project resources.

FAPESP 23/14214-4

A collection of papers, presentations, and resources related to our project "Development of structured catalysts for the photocatalytic synthesis of ammonia", funded by the Sao Paulo Research Foundation.

Published Papers

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CAP Alves, PH Palharim, B Pratto, AL da Silva, D Gouvêa & B Ramos. (2025). "Photocatalytic ammonia synthesis from nitrogen in water using iron oxides: Comparative efficiency of goethite, magnetite, and hematite". Journal of Photochemistry and Photobiology A: Chemistry, v. 460, p. 116159. DOI: 10.1016/j.jphotochem.2024.116159
Abstract Photocatalytic ammonia synthesis from nitrogen and water presents a promising pathway for decentralized sustainable ammonia production, leveraging the abundant solar energy. In this study, we explore the efficacy of three iron oxide polymorphs – goethite (α-FeO(OH)), magnetite (Fe3O4), and hematite (α-Fe2O3) – as photocatalysts for nitrogen reduction under ultraviolet (UV) light. The materials were synthesized using hydrothermal and polymeric precursor methods, characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), UV–Vis spectroscopy, photoluminescence spectroscopy, and thermal analysis to understand their structural, surface, and optoelectronic properties. Among the materials tested, goethite demonstrated the highest ammonia production rate (20.6 µmol g−1h−1), which we attribute to its larger specific surface area and the stability of its surface hydroxyl groups, which play a critical role in facilitating the protonation and electron transfer necessary for nitrogen reduction. Curiously, magnetite also displayed some activity (10.3 µmol g−1h−1), likely due to the formation of a heterojunction with the co-occurring goethite phase. Hematite showed the fastest area-based production rate (1.05 µmol m−2h−1), suggesting it is the polymorph with highest density of active sites for N2 reduction. This work contributes to the ongoing search for greener and lower-cost alternatives to the Haber-Bosch process, with implications for both agriculture and energy storage.
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AL Barbosa, RCO Romano, AA Bernardes, & D Gouvêa. (2025). "Rheological and microstructural characterization of titania pastes for additive manufacturing using polymeric ceramic precursor as organic and inorganic binder". Ceramics International, v. 51, p. 24072. DOI: 10.1016/j.ceramint.2025.03.093
Abstract Additive manufacturing (AM) is an innovative fabrication method that adds materials to build pieces, and it allows new ways to fabricate ceramic components with more complex and varied geometries. Among AM techniques, extrusion-based methods require carefully designed pastes with controlled rheological properties. This study develops and characterizes titania pastes incorporating a polymeric precursor as both a rheological modifier and a solid binder, optimizing their printability and post-processing behavior. Four different formulations were evaluated by varying composition and solid load, assessing their rheology, printability, and microstructural properties after calcination. The polymeric precursor, synthesized via the Pechini method, acted as an organic binder during drying and an inorganic binder after calcination, maintaining phase composition, and changing surface and grain boundary area, influencing mechanical properties. The results demonstrate that the polymeric precursor improves the processability of the paste, preserving the fidelity of the printing and allowing the obtaining of structures that maintain structural integrity. This approach introduces new opportunities for ceramic 3D printing, particularly in catalytic applications where tailored porosity and phase stability are critical.
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Papers Submitted

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CMF Ferreira, AL Barbosa, CAP Alves, AL da Silva, D Gouvêa & B Ramos. "Pechini-based reactive-binder ceramic suspension for direct ink writing of phase-pure structured SnO2 catalyst supports". Cerâmica. Submitted on Sept 2025.
Abstract Tin oxide (SnO2) is a chemically stable, redox-active metal oxide widely employed as a catalyst support in heterogeneous reactions, gas sensing, and energy-related applications. Here, we present a novel approach for the additive manufacturing of structured SnO2 catalyst supports via direct ink writing (DIW), utilising a Pechini-derived reactive binder. The ink formulation combines commercial SnO2 powder with a polymerisable complex of tin, citric acid, and ethylene glycol, which functions both as a rheological modifier and as a metal oxide precursor. This dual role eliminates the need for inert thickeners or non-native oxide binders. The resulting paste exhibits suitable viscoelastic properties for extrusion-based shaping and, upon calcination, the binder decomposes and converts to SnO2, complementing the original solid loading. The sintered pieces retain their geometric integrity, rendering them ideal for catalytic applications requiring high thermal and chemical stability. This reactive-binder strategy offers a straightforward, scalable, and compositionally clean route to structured metal oxide components, with potential applicability to other single or mixed oxide systems.
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Conference Presentations

2025
2024

Resources & Data

Project Overview: Photocatalytic Ammonia Synthesis (Poster, Portuguese)

The data generated from this project are available upon reasonable request. To request access, please provide a detailed rationale outlining the purpose and intended use of the data. All requests will be reviewed by the project team members.

Click here to request access to the project data.