Search Results (16)

Over the last decade, polymeric carbon nitrides (PCNs) have received exponentially growing attention as metal-free photocatalytic platforms for green energy generation and environmental remediation. Although PCNs can be easily synthesized from abundant precursors in a powdered form, progress in the field of photoelectrochemical applications requires effective methods for the fabrication of PCN films endowed with suitable mechanical stability and modular chemico-physical properties. In this context, as a proof-of-concept, we report herein on a simple and versatile chemical vapor infiltration (CVI) strategy for one-step PCN growth on porous Ni foam substrates, starting from melamine as a precursor compound. Interestingly, tailoring the reaction temperature enabled to control the condensation degree of PCN films from melem/melon hybrids to melon-like materials, whereas the use of different precursor amounts directly affected the mass and morphology of the obtained deposits. Altogether, such features had a remarkable influence on PCN electrochemical performances towards the oxygen evolution reaction (OER), yielding, for the best performing systems, Tafel slopes as low as ≈65 mV/dec and photocurrent density values of ≈1 mA/cm² at 1.6 V vs. the reversible hydrogen electrode (RHE). Full article

The performance of NiO-based supercapacitor electrodes for energy storage systems was enhanced by doping Cu into NiO thin films (200 nm) using radio-frequency magnetron co-sputtering on 3D porous Ni foam substrates, followed by rapid thermal annealing. The Hall effect measurements demonstrated enhanced electrical conductivity, with resistivity values of 1.244 × 10⁻⁴ Ω·cm. The 3D porous NiO:Cu electrodes significantly increased the specific capacitance and achieved a value of 1809.2 Fg⁻¹, with the NiO:Cu (10 at% Cu) thin films at a scan rate of 5 mVs⁻¹, which is a 2.67-fold increase compared with the undoped NiO films on a glass substrate. The 3D porous NiO:Cu electrodes significantly improved the electrochemical properties of the NiO-based electrode, which resulted in a higher specific capacitance for enhancing the energy storage performance during grid stabilization. Full article

Developing efficient bifunctional electrocatalysts with excellent stability at high current densities for overall water splitting is a challenging yet essential objective. However, transition metal phosphides encounter issues such as poor dispersibility, low specific surface area, and limited electronic conductivity, which hinder the achievement of satisfactory performance. Therefore, this study presents the highly efficient bifunctional electrocatalyst of CeO₂-modified NiFe phosphide on nickel foam (CeO₂/Ni₂P/Fe₂P/NF). Ni₂P/Fe₂P coupled with CeO₂ was deposited on nickel foam through hydrothermal synthesis and sequential calcination processes. The electrocatalytic performance of the catalyst was evaluated in an alkaline solution, and it exhibited an HER overpotential of 87 mV at the current density of 10 mA cm⁻² and an OER overpotential of 228 mV at the current density of 150 mA cm⁻². Furthermore, the catalyst demonstrated good stability, with a retention rate of 91.2% for the HER and 97.3% for the OER after 160 h of stability tests. The excellent electrochemical performance can be attributed to the following factors: (1) The interface between Ni₂P/Fe₂P and CeO₂ facilitates electron transfer and reactant adsorption, thereby improving catalytic activity. (2) The three-dimensional porous structure of nickel foam provides an ideal substrate for the uniform distribution of Ni₂P, Fe₂P, and CeO₂ nanoparticles, while its high conductivity facilitates electron transport. (3) The incorporation of larger Ce³⁺ ions in place of smaller Fe³⁺ ions leads to lattice distortion and an increase in defects within the NiFe-layered double hydroxide structure, significantly enhancing its catalytic performance. This research finding offers an effective strategy for the design and synthesis of low-cost, high-potential catalysts for water electrolysis. Full article

TiO₂ was loaded on the porous nickel foam from the suspended ethanol solution and used for the photocatalytic removal of NO_x. Such prepared material was heat-treated at various temperatures (400–600 °C) to increase the adhesion of TiO₂ with the support. Obtained TiO₂/nickel foam samples were characterized by XRD, UV–Vis/DR, FTIR, XPS, AFM, SEM, and nitrogen adsorption at 77 K. Photocatalytic tests of NO abatement were performed in the rectangular shape quartz reactor, irradiated from the top by UV LED light with an intensity of 10 W/m². For these studies, a laminar flow of NO in the air (1 ppm) was applied under a relative humidity of 50% and a temperature of 28 °C. Concentrations of both NO and NO₂ were monitored by a chemiluminescence NO analyzer. The adsorption of nitrogen species on the TiO₂ surface was determined by FTIR spectroscopy. Performed studies revealed that increased temperature of heat treatment improves adhesion of TiO₂ to the nickel foam substrate, decreases surface porosity, and causes removal of hydroxyl and alcohol groups from the titania surface. The less hydroxylated surface of TiO₂ is more vulnerable to the adsorption of NO₂ species, whereas the presence of OH groups on TiO₂ enhances the adsorption of nitrate ions. Adsorbed nitrate species upon UV irradiation and moisture undergo photolysis to NO₂. As a consequence, NO₂ is released into the atmosphere, and the efficiency of NO_x removal is decreasing. Photocatalytic conversion of NO to NO₂ was higher for the sample heated at 400 °C than for that at 600 °C, although coverage of nickel foam by TiO₂ was lower for the former one. It is stated that the presence of titania defects (Ti³⁺) at low temperatures of its heating enhances the adsorption of hydroxyl groups and the formation of hydroxyl radicals, which take part in NO oxidation. Contrary to that, the presence of titania defects in TiO₂ through the formation of ilmenite structure (NiTiO₃) in TiO₂/nickel foam heated at 600 °C inhibits its photocatalytic activity. No less, the sample obtained at 600 °C indicated the highest abatement of NO_x due to the high and stable adsorption of NO₂ species on its surface. Full article

Ni foam is an extensively used current collector and substrate in investigations of electrochemically active materials such as supercapacitors and electrocatalysts for oxygen and hydrogen evolution reactions. This material is relatively cheap, porous, and conductive and has a large specific surface area, all of which make it a good substrate. We investigated Ni-Mg ferrites and NiMn₂O₄ as active materials for electrochemical energy storage. These materials, when loaded on Ni foam, gave promising capacitance values: 172 F/g (at 2 mV/s) for NiMn₂O₄ in 6 M KOH and 242 F/g (at 2 mV/s) for MgFe₂O₄ in 3 M KOH. Nevertheless, during the authors’ work, many experimental problems occurred. Inconsistencies in the results directed further investigation towards measuring the capacitance of the active materials using GCE and platinum electrodes as substrates to discover if Ni foam was the culprit of the inconsistencies. When non-nickel substrates were used, both NiMn₂O₄ and MgFe₂O₄ showed reduced capacitance. Experimental problems associated with the utilization of Ni foam as a substrate for active materials in supercapacitor electrodes are discussed here, combined with other problems already addressed in the scientific literature. Full article

Ammonia (NH₃) is widely used in various fields, and it is also considered a promising carbon free energy carrier, due to its high hydrogen content. The nitrogen reduction reaction (NRR), which converts nitrogen into ammonia by using protons from water as the hydrogen source, is receiving a lot of attention, since effective process optimization would make it possible to overcome the Haber–Bosch method. In this study, we used a solution-based approach to obtain functionalized porous Ni foam substrates with a small amount of gold (<0.1 mg cm⁻¹). We investigated several deposition conditions and obtained different morphologies. The electrochemical performance of various catalysts on the hydrogen evolution reaction (HER) and NRR has been characterized. The ammonia production yield was determined by chronoamperometry experiments at several potentials, and the results showed a maximum ammonia yield rate of 20 µg h⁻¹ mg_cat⁻¹ and a Faradaic efficiency of 5.22%. This study demonstrates the potential of gold-based catalysts for sustainable ammonia production and highlights the importance of optimizing deposition conditions to improve the selectivity toward HER. Full article

Alkaline aqueous zinc-ion batteries possess a wider potential window than those in mildly acidic systems; they can achieve high energy density and are expected to become the next generation of energy storage devices. In this paper, a hollow porous P-NiCo₂O₄@Co₃O₄ nanoarray is obtained by ion etching and the calcination and phosphating of ZiF-67, which is directly grown on foam nickel substrate, as a precursor. It exhibits excellent performance as a cathode material for alkaline aqueous zinc-ion batteries. A high discharge specific capacity of 225.3 mAh g⁻¹ is obtained at 1 A g⁻¹ current density, and it remains 81.9% when the current density is increased to 10 A g⁻¹. After one thousand cycles of charging and discharging at 3 A g⁻¹ current density, the capacity retention rate is 88.8%. Even at an excellent power density of 25.5 kW kg⁻¹, it maintains a high energy density of 304.5 Wh kg⁻¹. It is a vital, promising high-power energy storage device for large-scale applications. Full article

Graphitic carbon nitride (gCN) is a promising n-type semiconductor widely investigated for photo-assisted water splitting, but less studied for the (photo)electrochemical degradation of aqueous organic pollutants. In these fields, attractive perspectives for advancements are offered by a proper engineering of the material properties, e.g., by depositing gCN onto conductive and porous scaffolds, tailoring its nanoscale morphology, and functionalizing it with suitable cocatalysts. The present study reports on a simple and easily controllable synthesis of gCN flakes on Ni foam substrates by electrophoretic deposition (EPD), and on their eventual decoration with Co-based cocatalysts [CoO, CoFe₂O₄, cobalt phosphate (CoPi)] via radio frequency (RF)-sputtering or electrodeposition. After examining the influence of processing conditions on the material characteristics, the developed systems are comparatively investigated as (photo)anodes for water splitting and photoelectrocatalysts for the degradation of a recalcitrant water pollutant [potassium hydrogen phthalate (KHP)]. The obtained results highlight that while gCN decoration with Co-based cocatalysts boosts water splitting performances, bare gCN as such is more efficient in KHP abatement, due to the occurrence of a different reaction mechanism. The related insights, provided by a multi-technique characterization, may provide valuable guidelines for the implementation of active nanomaterials in environmental remediation and sustainable solar-to-chemical energy conversion. Full article

Ni coatings with high catalytic efficiency were synthesised in this work, obtained by increasing the active surface and modifying Pd as a noble metal. Porous Ni foam electrodes were obtained by electrodeposition of Al on a nickel substrate. Deposition of Al was carried out with potential −1.9 V for a time of 60 min in NaCl–KCl-3.5 mol%AlF₃ molten salt mixture at 900 °C, which is connected with the formation of the Al-Ni phase in the solid state. Dissolution of Al and Al-Ni phases was performed by application of the potential −0.5 V, which provided the porous layer formation. The obtained porous material was compared to flat Ni plates in terms of electrocatalytic properties for ethanol oxidation in alkaline solutions. Cyclic voltammetry measurements in the non-Faradaic region revealed the improvement in morphology development for Ni foams, with an active surface area 5.5-times more developed than flat Ni electrodes. The catalytic activity was improved by the galvanic displacement process of Pd(II) ions from dilute chloride solutions (1 mM) at different times. In cyclic voltammetry scans, the highest catalytic activity was registered for porous Ni/Pd decorated at 60 min, where the maximum oxidation peak for 1 M ethanol achieved +393 mA cm⁻² compared to the porous unmodified Ni electrode at +152 mA cm⁻² and flat Ni at +55 mA cm⁻². Chronoamperometric measurements in ethanol oxidation showed that porous electrodes were characterised by higher catalytic activity than flat electrodes. In addition, applying a thin layer of precious metal on the surface of nickel increased the recorded anode current density associated with the electrochemical oxidation process. The highest activity was recorded for porous coatings after modification in a solution containing palladium ions, obtaining a current density value of about 55 mA cm⁻², and for a flat unmodified electrode, only 5 mA cm⁻² after 1800 s. Full article

Lately, ceramic fuel cells (CFCs) have held exceptional promise for joint small- and large-scale applications. However, the low-oxygen reduction response of cathode materials has hindered the low operating temperature of CFCs. Herein, we have developed a semiconductor based on La and Ce co-doped SrCoO₃ and embedded them in porous Ni-foam to study their electrochemical properties. The porous Ni-foam-pasted La_0.2Sr_0.8Co_0.8Ce_0.2O_3‒δ cathode displays small-area-specific resistance and excellent ORR (oxygen reduction reaction) activity at low operating temperatures (LT) of 450–500 °C. The proposed device has delivered an impressive fuel cell performance of 440 mW-cm⁻², using La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam substrate cathode operation at 550 °C with H₂ fuel and atmospheric air. It even can function well at a lower temperature of 450 °C. Moreover, La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam shows very good activation energy compared to individual SrCoO₃ and La_0.1Sr_0.9Co_0.9Ce_0.1O_3−δ embedded on porous Ni-foam, which help to promote ORR activity. Different characterization has been deployed, likewise: X-ray diffraction, photoelectron-spectroscopy, and electrochemical impedance spectroscopy for a better understanding of improved ORR electrocatalytic activity of prepared La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam substrate. These results can further help to develop functional cobalt-free electrocatalysts for LT-SOFCs. Full article

The in situ growth of metal organic framework (MOF) derivatives on the surface of nickel foam is a novel type of promising self-supporting electrode catalyst. In this paper, this work reports for the first time the strategy of in situ growth of Ni-MOF, where the metal source is purely provided by a nickel foam (NF) substrate without any external metal ions. MOF-derived Ni₂P/NPC structure is achieved by the subsequent phosphidation to yield Ni₂P on porous N, P-doped carbon (NPC) backbone. Such strategy provides the as-synthesized Ni₂P/NPC/NF electrocatalyst an extremely low interfacial steric resistance. Moreover, a unique three-dimensional hierarchical structure is achieved in Ni₂P/NPC/NF, providing massive active sites, short ion diffusion path, and high electrical conductivity. Directly applied as the electrode, Ni₂P/NPC/NF demonstrates excellent electrocatalytic performance towards both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with low overpotentials of only 58 mV and 208 mV to drive 10 mA cm⁻², respectively, in 1 M KOH. Furthermore, Ni₂P/NPC/NF acting as the overall water splitting electrodes can generate a current density of 10 mA cm⁻² at an ultralow cell voltage of 1.53 V. This simple strategy paves the way for the construction of self-supporting transition metal-based electrocatalysts. Full article

Herein, a facile one-step electrodeposition route was presented for preparing Ni₃S₂/NiS composite film on Ni foam substrate (denoted as NiS_x/NF). The NiS_x granular film is composed of mangy interconnected ultra-thin NiS_x nanoflakes with porous structures. When applied as electrodes for supercapacitors, the ultra-thin nanoflakes can provide more active sites for redox reaction, and the interconnected porous structure has an advantage for electrolyte ions to penetrate into the inner space of active materials quickly. As expected, the obtained NiS_x/NF sample exhibited high gravimetric capacitance of 1649.8 F·g⁻¹ and areal capacitance of 2.63 F·cm⁻². Furthermore, a gravimetric capacitance of 1120.1 F·g⁻¹ can be maintained at a high current density of 20 mA·cm⁻², suggesting a good rate capability. The influence of the different molar ratios of electrodeposition electrolyte (NiNO₃ and thiourea) on the morphology and electrochemical properties of NiS_x/NF sample was investigated to provide an optimum route for one-step electrodeposition of Ni₃S₂/NiS composite film. The outstanding performance indicated the Ni₃S₂/NiS composite film on Ni foam has great potential as an electrode material for supercapacitors. Full article

Hierarchical NiMoO₄/NiMoO₄ nanoflowers were fabricated on highly conductive flexible nickel foam (NF) substrates using a facile hydrothermal method to achieve rapid charge-discharge ability, high energy density, long cycling lifespan, and higher flexibility for high-performance supercapacitor electrode materials. The synthesized composite electrode material, NF/NiMoO₄/NiMoO₄ with a nanoball-like NF/NiMoO₄ structure on a NiMoO₄ surface over a NF substrate, formed a three-dimensional interconnected porous network for high-performance electrodes. The novel NF/NiMoO₄/NiMoO₄ nanoflowers not only enhanced the large surface area and increased the electrochemical activity, but also provided an enhanced rapid ion diffusion path and reduced the charge transfer resistance of the entire electrode effectively. The NF/NiMoO₄/NiMoO₄ composite exhibited significantly improved supercapacitor performance in terms of a sustained cycling life, high specific capacitance, rapid charge-discharge capability, high energy density, and good rate capability. Electrochemical analysis of the NF/NiMoO₄/NiMoO₄ nanoflowers fabricated on the NF substrate revealed ultra-high electrochemical performance with a high specific capacitance of 2121 F g⁻¹ at 12 mA g⁻¹ in a 3 M KOH electrolyte and 98.7% capacitance retention after 3000 cycles at 14 mA g⁻¹. This performance was superior to the NF/NiMoO₄ nanoball electrode (1672 F g⁻¹ at 12 mA g⁻¹ and capacitance retention 93.4% cycles). Most importantly, the SC (NF/NiMoO₄/NiMoO₄) device displayed a maximum energy density of 47.13 W h kg⁻¹, which was significantly higher than that of NF/NiMoO₄ (37.1 W h kg⁻¹). Overall, the NF/NiMoO₄/NiMoO₄ composite is a suitable material for supercapacitor applications. Full article

The membranes of a pillared-layer structure Metal-Organic Framework (MOF), [Ni(HBTC)(4,4′-bipy)] (HBTC = 1,3,5-Benzenetricarboxylic acid, 4,4′-bipy = 4,4′-bipyridine), have been in situ fabricated on Nickel foam substrate. The orientations of MOF crystals in the membranes can be controlled by the molar ratio of ligand H₃BTC to 4,4′-bipyridine. Scanning electron microscope images and powder X-ray diffraction patterns were used to characterize the membranes and confirm the orientations of their MOF layers. Control experiments have revealed that the presence of homologous metal element Nickel in both the MOF and the substrate and the presence of the neutral 4,4′-bipyridine in the reaction system are necessary for in situ growth of the well-intergrown MOF membranes. This work provides a successful example of directly growing continuous MOF layers on porous metallic substrate with desired orientations by a facile approach. Full article

This paper presents an electrode with a core/shell geometry and a unique four-layered porous wrinkled surface for pseudocapacitive supercapacitor applications. To design the electrode, Ni foam was used as a substrate, where the harmonious features of four constituents, ZnO (Z), NiS (N), PEDOT:PSS (P), and MnO₂ (M) improved the supercapacitor electrochemical performance by mitigating the drawbacks of each other component. Cyclic voltammetry and galvanostatic charge discharge measurements confirmed that the ZNPM hybrid electrode exhibited excellent capacitive properties in 2 M KOH compared to the ZNP, ZN, and solely Z electrodes. The ZNPM electrode showed superior electrochemical capacitive performance and improved electrical conductivity with a high specific capacitance of 2072.52 F g⁻¹ at 5 mA, and a high energy density of 31 Wh kg⁻¹ at a power density of 107 W kg⁻¹. Overall, ZNPM is a promising combination electrode material that can be used in supercapacitors and other electrochemical energy conversion/storage devices. Full article