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- 3D nickel foams with controlled morphologies for hydrogen evolution reaction in highly alkaline mediaPublication . Siwek, K. I.; Eugénio, S.; Santos, Diogo; Moura E Silva, Teresa; MONTEMOR, FATIMAWater electrolysis is the cleanest method for hydrogen production, and can be 100% green when renewable energy is used as electricity source. When the hydrogen evolution reaction (HER) is carried out in alkaline media, nickel (Ni) is a low cost catalyst and an interesting alternative to platinum. Still, its performance has to be enhanced to meet the high efficiency of the nobler metals, an objective that requires further tailoring of the surface area and morphology of Ni-based electrode materials. Unlike commercially available porous Ni, these features can be easily controlled via electrodeposition, a one-step process, taking advantage of the dynamic hydrogen bubble template (DHBT). Generally, changes in surface porosity and morphology have been mainly achieved by altering the main parameters, such as the current density or the deposition time. However, very scarce work has been done on the role of supporting electrolyte (i.e., its concentration and composition) in tailoring the foam features and consequently their catalytic activity. Hence, this approach paves the way to optimum design of metallic foam structures that can be obtained only with modifications in the electrolytic bath. In this work, 3D Ni foams are obtained from different composition baths by galvanostatic electrodeposition in the hydrogen evolution regime on stainless steel current collectors. Their porosity and morphology are analysed by optical microscopy and SEM. The electrochemical performance is evaluated by cyclic voltammetry, while catalytic activity towards HER and materials' stability in 8 M KOH are tested using polarisation curves and chronoamperometry measurements, respectively. The recorded high currents and extended stability of the Ni foams with dendritic morphology demonstrate its outstanding performance, making it an attractive cathode material for HER in highly alkaline media. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
- Carbon aerogels and xerogels: next-generation materials for sustainable energy and environmental solutionsPublication . Tomić, David; Radinović, Kristina; Mladenović, Dušan; Milikić, Jadranka; Santos, Diogo; Pombeiro, Armando; Paul, Anup; Sljukic Paunkovic, BiljanaAbstract Carbon aerogels and xerogels, with their 3D porous architectures, ultralow density, high surface area, and excellent conductivity, have emerged as multifunctional materials for energy and environmental applications. This review highlights recent advances in the synthesis of these materials via polymerisation, drying, and carbonisation, as well as the role of novel precursors such as graphene, carbon nanotubes, and biomass. Emphasis is also placed on doped and metal-decorated carbon gels as efficient electrocatalysts for oxygen reduction reactions, enabling four- and two-electron pathways for energy conversion and the production of green H2O2, respectively. Aerogels’ high specific capacitance and stability also position them as promising materials for supercapacitors. The versatility of carbon aerogels and xerogels offers exciting prospects for future innovations in catalysis, energy storage, and sustainable technologies.
- Low-cost transition metals (Fe, Ni, Co) on carbon aerogel for water electrolysis and supercapacitor applicationsPublication . Mladenović, Dušan; Martins, Marta; Samanci, Meryem; Charneca, Miguel; Paul, Anup; Santos, Diogo; Bayrakçeken, Ayşe; Sljukic Paunkovic, BiljanaAbstract Cost-effective transition metals (TM = Fe, Ni, Co) were immobilized on carbon aerogel (CA) using microwave irradiation, followed by nitrogen doping into one catalyst series through heat treatment. The physical characterization of the synthesized catalysts included N2 sorption, inductively coupled plasma-mass spectrometry, X-ray diffraction analysis, transmission electron microscopy, Raman spectroscopy, FTIR spectroscopy, and X-ray photoelectron spectroscopy. Co/CA displayed the best performance for oxygen evolution reaction (OER) electrocatalysis in alkaline water electrolysis, followed by Ni/CA. Co/CA exhibited a small Tafel slope of 110 mV dec−1 and required an overpotential of just 276 mV to reach 10 mA cm−2, lower than that of the commercial IrO2 electrocatalyst. Additionally, Co/CA and Ni/CA demonstrated excellent long-term stability during OER, with activity increasing over time. Capacitance measurements also showed the potential of TM/CA materials as supercapacitor electrodes. Fe/CA achieved the highest performance, with a specific capacitance of 322 F g-1 at a moderate current of 1 A g-1. It retained up to 96 % of its capacitance over 1000 cycles, indicating excellent stability.