Materials Science, Electrochemistry, Renewable Energy, Sustainability and the Environment, Surfaces, Coatings and Films
18
Scopus Publications
Scopus Publications
Sustainable nanocarbons via biocatalysis of C–F bond cleavage by electroactive bacteria Sarra Knani, Riad Ahmed Boughezal, Baptiste Cibron, Frédéric Barrière, Corinne Lagrost, Muriel Escadeillas, Ludivine Rault, Maida Costa de Oliveira, Paula E. Colavita, James A. Behan Carbon, 2026 Fluorographite is a promising starting material for the synthesis of graphene and graphene oxides via top-down exfoliation routes. C-F bonds in fluorographite can be chemically substituted to form graphene oxides with tuned surface chemistry. However, most defluorination routes reported proceed via fluorographene exfoliation from fluorographite followed by refluxing in organic solvents. Herein a one-pot, biogenic and aqueous route to graphene oxide nanomaterials directly from fluorographite with no pre-exfoliation step is demonstrated. Fluorographite incubation with the electroactive bacterial species Geobacter sulfurreducens yields water-dispersible graphene oxide quantum dots and partially-defluorinated graphene oxides as the main nanomaterial products in a single step. Biocatalysis at ambient temperature and pH proceeds through direct surface contact with bacteria through C-F bond cleavage, with fluorographite serving as the sole electron acceptor for exo -electrogenic respiration. This bioexfoliation strategy presents a sustainable and green synthetic route to functionalised carbon nanomaterials with tuneable size and surface properties under ambient conditions.
Single-Entity Electrochemistry of N-Doped Graphene Oxide Nanostructures for Improved Kinetics of Vanadyl Oxidation Maida Aysla Costa de Oliveira, Marc Brunet Cabré, Christian Schröder, Hugo Nolan, Filippo Pota, James A. Behan, Frédéric Barrière, Kim McKelvey, Paula E. Colavita Small, 2025 N‐doped graphene oxides (GO) are nanomaterials of interest as building blocks for 3D electrode architectures for vanadium redox flow battery applications. N‐ and O‐functionalities have been reported to increase charge transfer rates for vanadium redox couples. However, GO synthesis typically yields heterogeneous nanomaterials, making it challenging to understand whether the electrochemical activity of conventional GO electrodes results from a sub‐population of GO entities or sub‐domains. Herein, single‐entity voltammetry studies of vanadyl oxidation at N‐doped GO using scanning electrochemical cell microscopy (SECCM) are reported. The electrochemical response is mapped at sub‐domains within isolated flakes and found to display significant heterogeneity: small active sites are interspersed between relatively large inert sub‐domains. Correlative Raman‐SECCM analysis suggests that defect densities are not useful predictors of activity, while the specific chemical nature of defects might be a more important factor for understanding oxidation rates. Finite element simulations of the electrochemical response suggest that active sub‐domains/sites are smaller than the mean inter‐defect distance estimated from Raman spectra but can display very fast heterogeneous rate constants >1 cm s−1. These results indicate that N‐doped GO electrodes can deliver on intrinsic activity requirements set out for the viable performance of vanadium redox flow battery devices.
Carbon Thin-Film Electrodes as High-Performing Substrates for Correlative Single Entity Electrochemistry Marc Brunet Cabré, Christian Schröder, Filippo Pota, Maida A. Costa de Oliveira, Hugo Nolan, Lua Henderson, Laurence Brazel, Dahnan Spurling, Valeria Nicolosi, Pietro Martinuz, Mariangela Longhi, Faidra Amargianou, Peer Bärmann, Tristan Petit, Kim McKelvey, Paula E. Colavita Small Methods, 2025 Correlative methods to characterize single entities by electrochemistry and microscopy/spectroscopy are increasingly needed to elucidate structure‐function relationships of nanomaterials. However, the technical constraints often differ depending on the characterization techniques to be applied in combination. One of the cornerstones of correlative single‐entity electrochemistry (SEE) is the substrate, which needs to achieve a high conductivity, low roughness, and electrochemical inertness. This work shows that graphitized sputtered carbon thin films constitute excellent electrodes for SEE while enabling characterization with scanning probe, optical, electron, and X‐ray microscopies. Three different correlative SEE experiments using nanoparticles, nanocubes, and 2D Ti3C2Tx MXene materials are reported to illustrate the potential of using carbon thin film substrates for SEE characterization. The advantages and unique capabilities of SEE correlative strategies are further demonstrated by showing that electrochemically oxidized Ti3C2Tx MXene display changes in chemical bonding and electrolyte ion distribution.
Porous N-Doped Carbon-encapsulated Iron as Novel Catalyst Architecture for the Electrocatalytic Hydrogenation of Benzaldehyde Filippo Pota, Maida A. Costa de Oliveira, Christian Schröder, Marc Brunet Cabré, Hugo Nolan, Aran Rafferty, Olivier Jeannin, Franck Camerel, James A. Behan, Frédéric Barrière, Paula E. Colavita Chemsuschem, 2025 Carbon porous materials containing nitrogen functionalities and encapsulated iron‐based active sites have been suggested as electrocatalysts for energy conversion, however their applications to the hydrogenation of organic substrates via electrocatalytic hydrogenation (ECH) remain unexplored. Herein, we report on a Fe@C:N material synthesized with an adapted annealing procedure and tested as electrocatalyst for the hydrogenation of benzaldehyde. Using different concentrations of the organic, and electrolysis coupled to gas chromatography experiments, we demonstrate that it is possible to use such architectures for the ECH of unsaturated organics. Potential control experiments show that ECH faradaic efficiencies >70 % are possible in acid electrolytes, while maintaining selectivity for the alcohol over the pinacol dimerization product. Estimates of product formation rates and turnover frequency (TOF) values suggest that these carbon‐encapsulated architectures can achieve competitive performance in acid electrolytes relative to both base and precious metal electrodes.
Effects of N-functional groups on the electron transfer kinetics of VO2+/VO2+ at carbon: Decoupling morphology from chemical effects using model systems Maida A. Costa de Oliveira, Christian Schröder, Marc Brunet Cabré, Hugo Nolan, Antoni Forner-Cuenca, Tatiana S. Perova, Kim McKelvey, Paula E. Colavita Electrochimica Acta, 2024 Carbons and nanocarbons are important electrode materials for vanadium redox flow battery applications, however, the kinetics of vanadium species are often sluggish at these surfaces, thus prompting interest in functionalization strategies to improve performance. Herein, we investigate the effect of N-functionalities on the VO2+/VO2+ redox process at carbon electrodes. We fabricate thin film carbon disk electrodes that are metal-free, possess well-defined geometry and display smooth topography, while featuring different N-site distribution, thus enabling a mechanistic investigation of the intrinsic surface activity towards VO2+/VO2+. Voltammetry and electrochemical impedance spectroscopy show that N-functionalities improve performance, with pyridinic/pyrrolic-N imparting the most significant improvements in charge transfer rates and reversibility, compared to graphitic-N. This was further supported by voltammetry studies on nitrogen-free electrodes modified via aryldiazonium chemistry with molecular pyridyl adlayers. Computational modelling using an electrochemical-chemical mechanism indicates that introduction of surface pyridinic/pyrrolic-N can increase the heterogeneous rate constants by approximately two orders of magnitude relative to those observed at nitrogen-free carbon (k0 = 1.29 × 10−4 vs 9.34 × 10−7 cm/s). Simulations also suggest that these N-functionalities play a role in affecting reaction rates in the chemical step. Our results indicate that nitrogen incorporation via basic functional groups offers an interesting route to the design of advanced carbon electrodes for VRFB devices.
Iron-based electrocatalysts for energy conversion: Effect of ball milling on oxygen reduction activity Maida Aysla Costa de Oliveira, Pedro Pablo Machado Pico, Williane da Silva Freitas, Alessandra D’Epifanio, Barbara Mecheri Applied Sciences Switzerland, 2020 In this work, we synthesized new materials based on Fe(II) phthalocyanine (FePc), urea and carbon black pearls (BP), called Fe-N-C, as electrocatalysts for the oxygen reduction reaction (ORR) in neutral solution. The electrocatalysts were prepared by combining ball-milling and pyrolysis treatments, which affected the electrochemical surface area (ECSA) and electrocatalytic activity toward ORR, and stability was evaluated by cyclic voltammetry and chronoamperometry. Ball-milling allowed us to increase the ECSA, and the ORR activity as compared to the Fe-N-C sample obtained without any ball-milling. The effect of a subsequent pyrolysis treatment after ball-milling further improved the electrocatalytic stability of the materials. The set of results indicated that combining ball-milling time and pyrolysis treatments allowed us to obtain Fe-N-C catalysts with high catalytic activity toward ORR and stability which makes them suitable for microbial fuel cell applications.
