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

Paper Thumbnail
ILC Cunha, GC de Assis, P Metolina, PH Palharim, CA Gusmão, L Kulay, ACSC Teixeira & B Ramos. (2026). "Is Photocatalysis Ready for Scale Yet?". Processes, v. 14, n. 1, p. 102. DOI: 10.3390/pr14010102
Abstract Despite being frequently proposed as a low-carbon solution for wastewater treatment and solar fuel production, the feasibility of photocatalytic processes in large-scale deployments remains unclear. This review evaluates the scalability of photocatalytic technologies by synthesizing a decade (2015–2025) of techno-economic analysis (TEA) and life-cycle assessment (LCA) studies. Using a systematic search and programmatic screening, 77 assessment-focused publications were identified from an initial corpus of 854 studies. Across applications, TEA and LCA consistently highlight two dominant barriers to scale-up: high electricity demand in UV-driven systems and significant cradle-to-gate impacts associated with catalyst synthesis, particularly for nanostructured materials. When solar irradiation replaces artificial light, environmental and economic hotspots shift from energy use to material production, catalyst durability, and reuse assumptions. Wide variability in reported costs and impacts reflects heterogeneous methodologies, limited pilot-scale data, and a lack of standardized reporting. Overall, assessment-based evidence indicates that photocatalysis is not yet ready for widespread industrial deployment as a large industrial process. However, continuous advances in solar-driven reactor design, low-impact and circular catalyst synthesis, hybrid process integration, and harmonized TEA/LCA frameworks could substantially improve its prospects for scalable, climate-positive implementation, especially in the context of emerging green energy alternatives.
Read Open Access Paper
Paper Thumbnail
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.
Download Accepted Manuscript
Paper Thumbnail
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.
Download Accepted Manuscript

Papers Submitted

Paper Thumbnail
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. Preprint available at ChemRxiv DOI: 10.26434/chemrxiv-2025-7484d
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.
Download Preprint
Paper Thumbnail
CAP Alves, AL da Silva, VL Martins, B Ramos & D Gouvêa. "Grain Boundary Chloride Interface Segregation Enhances Conductivity in Hematite without Altering the Band Gap". Ceramics International. Submitted on Apr 2026.
Abstract Nanocrystalline Fe2O3 with controlled chloride additions was used to evaluate how interfacial Cl segregation governs grain-boundary electrical transport. XRF quantified the retained chloride, while selective surface lixiviation and interface-excess analysis separated surface from grain-boundary (GB) contributions, revealing preferential segregation at GBs. X-ray diffraction showed hematite with modest crystallite-size changes. UV-Vis reflectance spectroscopy indicated an almost invariant optical band gap (~2.18 eV), whereas the color difference increased with retained Cl-, consistent with defect/surface states. Room-temperature impedance spectroscopy resolved bulk and GB responses and showed a marked drop in resistivity with increasing Cl-; after lixiviation, conductivity partially decreased, confirming the interfacial origin. The rise in conductivity surpasses a simple carrier-count model (σ ∝ N), implicating mobility enhancement via GB-barrier lowering. Interfacial chloride segregation thus offers a practical route to increase the electrical conductivity of polycrystalline Fe2O3 without altering its band structure, advancing interface-engineered routes for electronic and photoelectrochemical applications.
Download Manuscript

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.

CAPES Move La America

This section compiles outputs from the CAPES Move La America project "Production of Lactic Acid via Fermentation Using Starch Extracted from Mango Seeds". Details will be updated as the project progresses.

Conference Presentations

2025