Rui Miguel da Silva Sampaio

Scopus Publications

Electrochemical exfoliation of graphite recovered from spent Li-ion batteries and its reuse as graphene in new electrodes
L.D. Chiavassa, R.S. Sampaio, M.F. Montemor
Sustainable Materials and Technologies, 2025
The growing demand for lithium-ion batteries, driven by the increasing number of electric vehicles, has led to rising volumes of end-of-life battery waste. In this work, a sustainable approach was developed for recovering graphite from spent LIBs and converting it into high-value electrode materials for electrochemical double-layer capacitors (EDLCs). Graphite was extracted from the anodes of spent NMC cells and functionalized via anodic electrochemical exfoliation under conditions optimized using the Taguchi method. The exfoliation parameters, namely applied potential, time, and temperature, were systematically studied to enhance the electrochemical performance of the resulting graphene oxide-based materials. The best-performing sample achieved a specific capacitance of 21 F g −1 at 0.1 A g −1 and retained 91 % of its initial capacitance after 10,000 charge/discharge cycles at 8 A g −1 . Additionally, a symmetric supercapacitor cell assembled using the optimized sample (E9) demonstrated comparable performance to commercial activated carbon (YP50), confirming its practical viability. This study highlights the potential of recycled graphite as a sustainable precursor for graphene-based electrodes, contributing to the development of environmentally friendly energy storage technologies, aligned with circular economy principles.
Reuse of graphite from spent lithium-ion batteries: Graphite@MnOx composites for high-performance supercapacitor application
Nishat S. Khan, Maryna Taryba, R.G. Duarte, M.F. Montemor, R.S. Sampaio
Sustainable Materials and Technologies, 2025
This study investigates the reuse of graphite recovered from spent lithium-ion batteries for supercapacitor applications. Lithium-ion batteries currently dominate the energy storage market and generate significant waste, which contains valuable metal compounds. Effectively recycling these materials provides a sustainable source of raw materials and supports the circular economy by enabling their direct reuse in new electrochemical storage systems. However, developing novel recycling methods requires simple yet effective strategies to obtain ready-to-use active materials. In this research, recovered graphite is combined with MnO 2 to create a composite using a single-step electroless process. The resulting composite was tested as an electrode in a Na 2 SO 4 electrolyte, demonstrating promising electrochemical performance. Electrochemical results were discussed in light of the morphological and structural material properties. Furthermore, a symmetric cell was assembled, achieving a high specific capacitance of 28.6 F g −1 at a current density of 0.6 A g −1 . It also exhibited excellent high-rate capability and remarkable cycling stability over 5000 cycles, with a capacitance retention of 80.2 %. These results highlight the potential of reusing recycled graphite as a cost-effective and locally sourced electrode material for more sustainable energy storage applications.
New insights into the degradation of pseudocapacitive MnOx under floating
R.S. Sampaio, J.P. Correia, T.M. Silva, M.F. Montemor
Journal of Energy Storage, 2025
This work discusses the degradation of a potentiostatically grown MnO x electrode under floating at different applied potentials through electrochemical impedance spectroscopy and in-situ ellipsometry. The findings revealed that increasing the floating potential above the optimum anodic limit (1.0 V vs. SCE) leads to an exponential increase in electrode degradation and, consequently, a decrease in the total failure time. The ohmic drop increases with the floating time and evolves linearly with increasing applied potential. EIS results showed that the electrodes' degradation during floating tests is mainly structural and related to inner pores collapse and blockage, consequently decreasing inner layer active sites. The electrolyte resistance in the inner pores increases, and the inner layer capacitance decreases linearly with the floating time. The floating test at 1.2 V was also followed by in-situ ellipsometry. After the aging test, the electrode presented reduced film thickness from 138 to 136 nm, reduced porosity (> n ), and increased resistivity (< k ). Initially, the MnO x electrode presents a capacitive response dominated by the inner surface processes of about 68 %. As the electrode is subjected to floating pulses, the total capacitance decreases and starts to be dominated by the outer processes' charge contribution, representing 74 % of the total charge contribution at the end of the floating test.
Corrosion and solid-state properties of Nb2O5 coating deposited on Ti-6Al-4V Alloy via DC reactive sputtering
João Pedro Lopes do Nascimento, Murilo Oliveira Alves Ferreira, Rogério Valentim Gelamo, Rui Miguel da Silva Sampaio, Natália Bueno Leite Slade, Jéferson Aparecido Moreto, João Carlos Salvador Fernandes
Electrochimica Acta, 2025
• The reactive sputtering technique was advantageous for the deposition of Nb 2 O 5 on the Ti-6Al-4 V alloy. • Ti-6Al-4V/Nb 2 O 5 exhibits superior corrosion resistance compared to bare Ti-6Al-4 V alloy. • The Nb 2 O 5 coating deposited on Ti-6Al-4 V alloy surfaces by DC reactive sputtering exhibits n-type semiconducting characteristics. • The modified electrode surface presented a lower Urbach energy. • An evident relationship exists between the solid-state properties of the Nb₂O₅ coating and its ability to enhance the corrosion resistance of the Ti-6Al-4 V alloy. This study investigates the surface modification of Ti-6Al-4V alloy substrates via Nb₂O₅ coatings deposited through reactive sputtering. The solid-state properties and corrosion behaviour of the Nb₂O₅ coatings were analysed using electrochemical techniques and optical ellipsometry. The results demonstrate a significant enhancement in the corrosion resistance of the Ti-6Al-4V/Nb₂O₅ system compared to the uncoated alloy. The Nb₂O₅ thin film exhibits n-type semiconducting behaviour with a donor concentration of approximately 10¹⁶ cm⁻³. Photoelectrochemical studies revealed energy band gaps of 3.39 eV for Ti-6Al-4V and 3.27 eV for Ti-6Al-4V/Nb₂O₅ and a lower Urbach energy (0.44 eV) for the coated system compared to the substrate (0.68 eV), indicating that the coatings produced via reactive sputtering effectively reduced the energy states linked to defects and imperfections, acting as a passivating layer for the Ti-6Al-4V surface and enhancing its corrosion resistance. These findings establish a clear relationship between the solid-state properties of the Nb₂O₅ coating and its ability to enhance the corrosion resistance of the Ti-6Al-4V alloy.
Biochar-Ni nanocomposites derived from broccoli as an efficient ecoconscious approach for sustainable supercapacitive materials
Pablo Arévalo-Cid, Lorena Alcaraz, R.S. Sampaio, Felix A. López-Gómez, Patrícia A. Carvalho, M.F. Montemor, Marta M. Alves
Journal of Energy Storage, 2025
The increasing need for energy storage systems in the transition to renewable energy is accelerating the search for sustainable raw materials, with hyperaccumulator plants offering unique, untapped sources by capturing and processing electroactive metals like nickel (Ni) into their carbon matrix. In this study, we investigated broccoli's ability to absorb and process Ni, a metal that significantly contributes to enhanced energy storage capacity. Unlike traditional phytoremediation, we focused on producing carbon-based materials with electrochemical performance rather than environmental recovery. To demonstrate our ecoconscious concept, broccoli plants were exposed to varying Ni concentrations (0, 0.4, 0.8, 1.6, and 3.2 g/L) over 10 weeks, producing shoot dry biomass with Ni contents from <20 to 492 mg Ni/kg. Following pyrolysis at 650 °C, the resulting biochar was used as electroactive material for supercapacitor applications. Surprisingly, the best performance was observed in plants with 152 mg Ni/kg, with the bionanocomposite exhibiting a specific capacitance of 38 F/g at the scan rate of 100 mV/s and excellent capacitance retention of 94 % over 5000 cycles at 10 A/g. The supercapacitor prototype presented a maximum energy density of 0.762 Wh/kg at 184 W/kg power density. This unexpected finding suggests altered plant metabolism as a potential explanation, offering new insights and raising scientific questions about engineering hyperaccumulator plants for sustainable energy storage applications. • Hyperaccumulators were grown in soil with cumulative Ni up to 3.2 g/L over 10 weeks • Shoots with Ni <20 to 492 mg Ni/kg were used as electrode material after pyrolysis • The best electrochemical performance was observed in shoots with 152 mg Ni/kg • This bionanocomposite exhibited a specific capacitance of 38 F/g at 100 mV/s • Altered plant metabolism and/or lignocellulosic depolymerisation were hypothesised to affect electrochemical metrics
Electrochemical growth optimization of IrOx films on stainless steel as electrodes for high performance supercapacitors
Arcílio B.S. Semente, R.S. Sampaio, T.M. Silva, M.F. Montemor
Electrochimica Acta, 2025
Iridium oxide (IrOx) films were electrochemically deposited using cyclic voltammetry , varying the number of cycles and the scan rates to analyze their role in the electrochemical performance of the modified electrodes. The number of cycles was varied as 20, 40, 60 and 80 cycles, and the scan rates were varied as 25, 36, 42 and 50 mV s -1 . The SEM analysis showed that initially there is the formation of a homogenous layer of small iridium oxide nuclei and, as the films grow thicker, the nuclei start to merge and form nuclei with larger diameters. The electrochemical characterization was carried out in a three-electrode setup using 1 M Na 2 SO 4 with a potential window of 1.2 V vs SCE. The highest specific capacitance was approximately 445 F g -1 , obtained by a sample synthesized at a scan rate of 50 mV s -1 with 40 cycles. The same sample exhibited a capacitance retention of 98.15 % after 5000 cycles at 50 A g -1 . Moreover, it also displayed a 91.2 % capacitance retention after 50,000 cycles at 50 A g -1 . These results show the potential use of this material for supercapacitor applications where reliability and safety are key parameters rather than investment costs.
Effect of ZnAl-NO2 LDH on chloride entrapment and protection of iron reinforcement in mortar samples
R.S. Sampaio, C. Gomes, A.C. Bastos, M.G.S. Ferreira
Journal of Building Engineering, 2024
Sustainable graphene production for solution-processed microsupercapacitors and multipurpose flexible electronics
Siva Sankar Nemala, João Fernandes, João Rodrigues, Vicente Lopes, Rui M.R. Pinto, K.B. Vinayakumar, Ernesto Placidi, Giovanni De Bellis, Pedro Alpuim, Rui S. Sampaio, Maria F. Montemor, Andrea Capasso
Nano Energy, 2024
The growing demand for portable and wearable electronics, Internet of Things microdevices, and wireless sensor networks has led to the development of miniaturized energy storage devices, such as microsupercapacitors (mSCs). With excellent electrical conductivity and high surface area in a layered structure, graphene materials are ideal for mSCs, but current manufacturing methods still hinder their widespread integration. Here, we propose a sustainable approach for the rapid and eco-friendly production of few-layer graphene flakes based on the exfoliation of graphite in water by a combination of high-shear mixing and a high-pressure airless spray. An all-carbon composite paste with high electrical conductivity and tunable viscosity was designed to fabricate planar, interdigitated mSCs on polyethylene terephthalate (PET). The flexible, metal-free mSCs achieved a Coulombic efficiency close to 100%, with areal and volumetric capacitances of 6.16 mF cm-2 and 2.46 F cm-3, respectively. The maximum energy density exceeds 200 μWh cm-3 with 91.5% capacitance retention after 10000 galvanostatic chargedischarge cycles. The mSCs retain the same performance when subjected to a wide bending range and can be easily modularized to adjust the voltage and capacitance outputs. Finally, high-performance coatings for electromagnetic interference shielding and wearable strain sensors are also fabricated to demonstrate the multipurpose applicability of the graphene-based paste.
In Situ Ellipsometry and EIS Study of Potentiostatic Synthesis of Pseudocapacitive MnOx
R. S. Sampaio, T. M. Silva, M. F. Montemor
Journal of the Electrochemical Society, 2023
This work discusses the one-step potentiostatic growth of manganese oxide on stainless steel for pseudocapacitor electrodes. The electrode material was studied through in situ ellipsometry and electrochemical impedance spectroscopy, in order to correlate its microstructure with the capacitive response. Ellipsometry results show the formation of three layers during the potentiostatic synthesis of manganese oxide on stainless steel: the thickening of the native oxide of the substrate, and the growth of two distinct layers of manganese oxide. The inner layer is slightly more compact (>n) and more resistive (<k) than the outer one. The electrochemical characterization of modified electrodes showed that the increase in the growth potential (from 0.7 to 1.0 VSCE) leads to the formation of manganese oxide films with higher specific capacitance (from 64 to 330 F g−1 at 2 A g−1). This effect is due to an increase in the area of the active material and to a decrease in the thickness of the inner layer of the manganese oxide film. However, higher growth potentials also lead to an increase in film resistivity due to the increase in the density and thickness of the outer layer, which hinders the diffusion of ions through the film as evidenced by EIS.
New Sensors for Monitoring pH and Corrosion of Embedded Steel in Mortars during Sulfuric Acid Attack
Rui Sampaio, Alexandre Bastos, Mário Ferreira
Sensors, 2022
The sulfuric acid attack is a common form of degradation of reinforced concrete in contact with industrial wastewater, mine water, acid rain, or in sewage treatment stations. In this work, new pH-sensitive IrOx electrodes were developed for monitoring the pH inside mortar or concrete. To test their ability, the pH sensors were embedded in mortar samples at different depths and the samples were exposed to sulfuric acid solution. In another set of experiments, iron wires were placed at the same depths inside similar mortar samples and their corrosion was monitored as the acid attacked the mortar. Severe acid attack led to cement dissolution and formation of gypsum. The new pH sensors succeeded in measuring the pH changes inside the mortars. The pH gradient, from the high acid environment to the high alkaline mortar interior, occurred in a narrow region. Corrosion of the iron electrodes started only when the acidic solution was in their close vicinity.
The Stability and Chloride Entrapping Capacity of ZnAl-NO2 LDH in High-Alkaline/Cementitious Environment
Zahid M. Mir, Celestino Gomes, Alexandre C. Bastos, Rui Sampaio, Frederico Maia, Cláudia Rocha, João Tedim, Daniel Höche, Mario G. S. Ferreira, Mikhail L. Zheludkevich
Corrosion and Materials Degradation, 2021
Use of ZnAl-Layered double Hydroxide (LDH) to extend the service life of reinforced concrete
Celestino Gomes, Zahid Mir, Rui Sampaio, Alexandre Bastos, João Tedim, Frederico Maia, Cláudia Rocha, Mário Ferreira
Materials, 2020
Enhanced Predictive Modelling of Steel Corrosion in Concrete in Submerged Zone Based on a Dynamic Activation Approach
Zahid Mohammad Mir, Daniel Höche, Celestino Gomes, Rui Sampaio, Alexandre C. Bastos, Philippe Maincon, M. G. S. Ferreira, Mikhail L. Zheludkevich
International Journal of Concrete Structures and Materials, 2019

Rui Miguel da Silva Sampaio

RESEARCH, TEACHING, or OTHER INTERESTS

Scopus Publications