Metallic Ni Nanoparticles Research Articles

Highly Efficient and Selective Hydrodeoxygenation of Guaiacol Using Ni-Supported Honeycomb-Structured Biochar and Phosphomolybdic Acid.

The sustainable development of energy has always been a concern. Upgrading biomass catalysis into hydrocarbon liquid fuels is one of the effective methods. In order to upgrade biomass derivative guaiacol by Hydrodeoxygenation (HDO) catalysis, this article report a three-dimensional honeycomb structure biochar loaded with Ni nanoparticles and phosphomolybdic acid demonstrating excellent catalytic performance in a short period of time. This is due to the porous structure of biochar, which allows Ni metal nanoparticles to be highly uniformly dispersed on the support, which enhances the catalytic hydrogenation of guaiacol in terms of both rate and efficiency. Furthermore, it was observed that the added phosphomolybdic acid dissolved within the temperature range of 78-90°C, functioning as a homogeneous catalyst in the process. This proves advantageous, as the phosphomolybdic acid becomes accessible at any location within the porous Ni/C catalyst. The detailed characterization data revealed that the carbon support prepared in this study has a high specific surface area of up to 1375.61 m2/g. Additionally, the phosphomolybdic acid exhibited rich acidity, with Brønsted and Lewis acid contents of 2.55 μmol/g and 21.45 μmol/g, respectively. Reaction data demonstrated that at 240°C for 180 minutes, 100% conversion and 97.9% cyclohexane selectivity were achieved.

In-situ exsolved Ni nanoparticles for boosting CO2 reduction in solid oxide electrolysis cell

Due to their excellent high Faraday efficiency, perovskite solid oxide cells (SOECs) have attracted considerable attention. Nevertheless, they still face significant challenges in terms of stability and electrocatalytic activity during CO₂ electrolysis. In this study, Ni particles in La0.65Ba0.35Mn1-xNixO3-δ are successfully separated by a unique in-situ exsolved method of metal nanoparticles, which are uniformly anchored to the electrode surface as Ni nanometal particles. This effectively suppresses the generation of carbon deposits on the cathode surface. Under test conditions of 850 °C, 1.6 V and 50 sccm flow rate, the CO yield of the modified cathode material reached 5.9 mL min−1 cm−2, which is nearly four times higher than that before doping. The synergistic effect of in-situ exsolution of Ni metal nanoparticles with oxygen defects generated by the perovskite, creating more active locations for CO2 adsorption and electrolysis, is responsible for the significant improvement in electrochemical performance. This work provides new strategies and ideas for the development of efficient and durable SOEC cathode materials.

Anchoring nickel sites on ceria-coated silica to enhance the catalytic stability for the vapor phase levulinic acid hydrogenation

The preparation of the binary metal NiCe-based catalysts involved a 2-step protocol, the ceria was first coated on SiO2 which was then utilized to disperse Ni nanoparticles. Various techniques including N2 adsorption/desorption, ICP-OES, XRD, HRTEM, XPS, H2-chemisorption, H2-TPR, NH3-TPD, and TG etc. were performed to study the microstructure, redox, acid property and deactivation. The results revealed that CeO2 and metallic Ni were well dispersed on the support surface, the synergistic effect between the two metal species was conserved well. The content of CeO2 had considerable effects on redox and metallic properties rather than the acidic property. The dispersion of metallic Ni played a dominant role in promoting the catalytic activity. The levulinic acid conversion attained 84.0 % with a γ-valerolactone selectivity of 98.8 % on Ni/SiO2@2CeO2 sample with the highest dispersion of 9.8 %. The amorphous CeO2 suppressed the sintering of metallic Ni nanoparticles and improved the coke resistance, leading to better catalytic activity within 20 h time on stream.

Modulation of Selectivity and Activity of Ni/TiO2 Catalysts by Metal Dispersion in Photothermal CO2 Hydrogenation

Ni/TiO2 catalysts are efficient and cost‐effective for photothermal CO2 hydrogenation. However, the achieved CO/CH4 ratio strongly depends on the specific characteristics of these catalysts. To further ascertain the role of metal dispersion and photoactivation on selectivity, in this work we investigate the impact of Ni loading over high surface area anatase on the photothermal performance. Catalysts with 3 and 10 wt. % of Ni prepared by incipient wetness impregnation show initial good dispersion of the metal, although after activation in H2 metallic Ni nanoparticles are observed for 10%Ni/TiO2. This last catalyst demonstrates superior CO2 hydrogenation activity at high temperature, but below 200 ºC it is overpassed by the catalyst with 3 wt % Ni/TiO2. The selectivity varies remarkably with Ni loadings. Thus, at 350 °C about 93 % of methane is obtained over 10 wt.% Ni/TiO2, while 3%Ni/TiO2 yields about 97 % of CO. Low‐intensity UV irradiation enhances performance, particularly at temperatures below 200 ºC, where an increment in the production of methane of up to 75 % is observed for 3 wt.% Ni/TiO2 at 200 ºC. These results highlight the influence of metal dispersion, along with irradiation on modulating the selectivity of the photothermal CO2 hydrogenation

Enhancing Electrochemical Efficiency of Solid Oxide Electrolysis Cells for Carbon Dioxide Reduction Through Nickel‐Doped Titanate‐Based Cathode with Doped Ceria Electrolyte

AbstractSolid oxide electrolysis cell (SOEC) is a potential technology for converting the principal greenhouse gas, carbon dioxide (CO2), into carbon monoxide (CO) by employing renewable energy. SOECs have great potential, including high‐energy efficiency, fast electrode kinetics, and competitive cost; however, this technology still has challenges in developing highly active, robust CO2 cathode electrocatalysts. In this work, we report the Ni‐doped lanthanum strontium calcium titanate (La0.20Sr0.25Ca0.45Ni0.05Ti0.95O3−δ) cathode for application as the cathode of CO2 electrolysis with gadolinia‐doped ceria (Gd0.1Ce0.9O1.95) electrolyte in SOEC. The exsolution of Ni nanoparticles is achieved by a simple in situ growth method at 800 °C. The Ni doping in LSCT significantly improved the electrochemical activity of the catalyst by increasing oxygen vacancies, and the Ni metallic nanoparticles can afford much more active sites for CO2 reduction. The CO2 electrolysis mechanism is studied by the distribution of relaxation time analysis of impedance spectroscopy. Ni‐LSCT renders a higher activity for electrolysis of CO2 with an exceptionally high reduction current density of 3.89 A cm−2 at 2.5 V potential applied and 800 °C temperature with GDC (Gd0.1Ce0.9O1.95) electrolyte. Ni doping is a crucial factor in controlling the electrochemical performance and catalytic activity in SOEC and GDC electrolytes, which is further helped by the high ionic conductivity.

Supported Ni nanoparticles derived from MOFs as a highly active catalyst for benzene hydrogenation

Metal-organic frameworks (MOFs) is easy to agglomerate at high temperature, resulting in the rapid collapse of the MOFs structure and the aggregation of metal sites. In this paper, Al2O3 is used as the support material to support the in-situ synthesis of Ni-MOF on the surface, and the metal Ni nanoparticles are successfully fixed on the Al2O3. The results showed that both Ni/Ni-MOF-300 and Ni/NA-MOF-300 catalysts reduced at 300 ℃ have good hydrogenation activity of benzene, and Ni/Ni-MOF-450 catalysts reduced at 450 ℃ formed huge Ni aggregates, which significantly reduced the hydrogenation activity of benzene. However, Ni/NA-MOF-450 catalyst reduced at 450 ℃ can effectively resist the metal Ni agglomeration caused by the collapse of MOFs structure at high temperature, and has better hydrogenation activity of benzene.

Highly efficient enhancement of mechanical and tribological properties of Cu-based composites by addition of graphene-loaded Ni metal particles

The tight interface between graphene and Cu is the key to give full play to the comprehensive properties of Cu/C composites. In this study, reduced graphene oxide(RGO) was used as a reinforcing phase of Cu marix, and the interfacial bonding strength between RGO and Cu was enhanced by introducing Ni metal nanoparticles. RGO supported Ni nanosheets (Ni-RGO) were successfully prepared by in-situ chemical reduction of graphene oxide (GO) and the introduction of Ni nanoparticles into GO. Ni nanoparticles were tightly attached to the graphene sheets. The mechanical properties and tribological properties of Ni-RGO/Cu composites were significantly improved. The bending strength of Ni-RGO/Cu composites reached 162.2 MPa, which was much higher than that of the pure Cu. At the same time, Ni-RGO composites have the lowest wear rate, and the friction coefficient is stable between 0.1 and 0.2. The comprehensive performance of Ni-RGO composites is significantly enhanced due to the unique structure of Ni-RGO, and the introduction of Ni nanoparticles realizes the effective bonding between GO-Ni-Cu. This study provides a new and effective strategy for enhancing the interfacial bonding of Cu/C composites.

Insights into interfacial catalysis for aqueous reduction of 4-Nitrophenol catalyzed by Ni metal nanoparticles encapsulated within biomass-derived N-doped carbon matrix

As we strive towards a sustainable future in the field of catalysis, it is imperative to draw inspiration from Mother Nature. In this study, we present a straightforward and environmentally friendly approach for the in situ synthesis of nickel metal nanoparticles encapsulated within nitrogen-doped carbon (NNC), derived from daikon biomass. Among the various examined NNC catalysts, NNC-2 characterized by its substantial surface area and high doping content, emerges as the most promising candidate for catalyzing the reduction of 4-nitrophenol. Ab initio molecular dynamics simulations unveil that NNC-2 facilitates a robust Ni-NC interfacial interaction, which stabilizes Ni nanoparticles and supports the exceptional durability and recyclability. Theoretical calculations further elucidate the structure–activity relationship of the catalyst and the mechanistic aspects of the surface reduction of 4-nitrophenol. This insight enhances our understanding of the catalytic processes over carbon-based catalysts, providing a foundation for optimizing catalytic performance and guiding future developments in the field.

Ultrafine Ni-MoOx Nanoparticles Anchored on Nitrogen-Doped Carbon Nanosheets: A Highly Efficient Noble-Metal-Free Catalyst for Ammonia Borane Hydrolysis.

The development of low-cost and high-efficiency catalysts for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) is still a challenging technology. Herein, ultrafine MoOx-doped Ni nanoparticles (~3.0 nm) were anchored on g-C3N4@glucose-derived nitrogen-doped carbon nanosheets via a phosphate-mediated method. The strong adsorption of phosphate-mediated nitrogen-doped carbon nanosheets (PNCS) for metal ions is a key factor for the preparation of ultrasmall Ni nanoparticles (NPs). Notably, the alkaline environment formed by the reduction of metal ions removes the phosphate from the PNCS surface to generate P-free (P)NCS so that the phosphate does not participate in the subsequent catalytic reaction. The synthesized Ni-MoOx/(P)NCS catalysts exhibited outstanding catalytic properties for the hydrolysis of AB, with a high turnover frequency (TOF) value of up to 85.7 min-1, comparable to the most efficient noble-metal-free catalysts and commercial Pt/C catalyst ever reported for catalytic hydrogen production from AB hydrolysis. The superior performance of Ni-MoOx/(P)NCS can be ascribed to its well-dispersed ultrafine metal NPs, abundant surface basic sites, and electron-rich nickel species induced by strong electronic interactions between Ni-MoOx and (P)NCS. The strategy of combining multiple modification measures adopted in this study provides new insights into the development of economical and high-efficiency noble-metal-free catalysts for energy catalysis applications.

Two-in-one strategy for optimizing chemical and structural properties of carbon felt electrodes for vanadium redox flow batteries

ABSTRACT Vanadium redox flow batteries (VRFBs) have received significant attention for use in large-scale energy storage systems (ESSs) because of their long cycle life, flexible capacity, power design, and safety. However, the poor electrochemical activity of the conventionally used carbon felt electrode results in low energy efficiency of the VRFBs and consequently impedes their commercialization. In this study, a carbon felt (CF) electrode with numerous nanopores and robust oxygen-containing functional groups at its edge sites is designed to improve the electrochemical activity of a carbon felt electrode. To achieve this, Ni metal nanoparticles were initially precipitated on the surface of the CF electrode, followed by etching of the precipitated Ni nanoparticles on the CF electrode using sulfuric acid. The resulting CF electrode had a specific surface area eight times larger than that of the pristine CF electrode. In addition, the oxygen-containing functional groups anchored at the graphite edge sites of the nanopores can act as robust electrocatalysts for VO2+/VO2 + and V2+/V3+ redox reactions. Consequently, the VRFB cell with the resulting carbon felt electrode can deliver a high energy efficiency of 86.2% at the current density of 60 mA cm−2, which is 20% higher than that of the VRFB cell with the conventionally heat-treated CF electrode. Furthermore, the VRFB cell with the resultant carbon felt electrodes showed stable cycling performance with no considerable energy efficiency loss over 200 charge-discharge cycles. In addition, even at a high current density of 160 mA cm−2 , the developed carbon felt electrode can achieve an energy efficiency of 70.1%.

Ni-doped sites in yeast-derived catalysts for efficient electrochemical synthesis of hydrogen peroxide

The electrochemical synthesis of hydrogen peroxide (H2O2) via the 2-electron pathway of oxygen reduction reaction offers a green and on-site product. However, there remains an urgent need to develop cost-efficient electrocatalysts with H2O2 productivity that meets practical industrial-scale requirements. In this study, yeast-derived carbon material loaded with multiple Ni active sites achieved electrochemical synthesis of H2O2 at industrial current density. The precursor of heteroatom-doped carbon material was obtained through high-dispersed Ni(II) adsorption on yeast cells. By adjusting the pyrolysis temperature and Ni loading dosage, the carbon framework, pore structure, and Ni active sites within the obtained Ni/yeast were successfully regulated. Ni/yeast featured with highly active Ni single-atom sites, metallic Ni nanoparticles and Ni2P nanoparticles, enabling stable running for 10 h at 200 mA cm−2 in a flow cell. Ni/yeast exhibits remarkable H2O2 Faradaic efficiency of 94.6 % and a yield of 35.3 mol gcat−1h−1. The abundant pore structure and multiple Ni active sites within Ni/yeast provide promising avenues for manipulating heteroatom-doped carbon materials in H2O2 electrosynthesis.

Electronic Regulation on Ni‐based Catalysts for Efficient CO2 Electroreduction

AbstractGreen power‐driven CO2 electroreduction using earth‐abundant Ni‐based catalysts is a highly promising approach to fulfill renewable energy storage and a negative carbon cycle. However, metallic Ni nanoparticles and clusters always show severe hydrogen evolution during CO2 electroreduction. Single atomic Ni catalysts demonstrate promising performance for CO2 electroreduction, whereas the very weak binding to intermediates and the very low metal loadings severely limit their activity, efficiency, and practical application. In this concept, we discuss how to regulate the electronic structures of Ni‐based catalysts to enhance the activity and selectivity of CO2 electroreduction. This work will offer instructive guidance in elaborating transition metal catalysts for highly efficient CO2 electroreduction, which may become suitable for future industrial applications.

Synergistically catalytic regulation of surface chemistry on coal based needle coke by bimetallic interface for enhanced Li/Na storage

The oxygen functional groups (OFGs) on carbon surface are electrochemically active for rapid Li/Na storage, and always are introduced with environment-hazardous and time-consuming ways. Herein, the bimetallic synergistic effect between Fe and Ni metal nanoparticles is proved experimentally to promote the conversion from useless C–O groups to useful CO groups on the surface of needle coke (NC) greatly. In addition, the DFT calculations show that introducing second metals increase the active electrons of single metals, and the activity of transforming C–O bond to CO bond thus makes a difference in bimetallic systems. Among the modified samples, Fe/Ni-NC contains abundant CO groups, stripe like graphite domains, excellent electronic conductivity and large interlayer spacing. Therefore, Fe/Ni-NC anode shows the excellent capacities in half batteries (212/305.2 mA h g−1 after 1000/2000 cycles at 2.0/5.0 A g−1 in SIB/LIB) and full batteries (86/145 mA h g−1 in SIB/LIB at 0.05 A g−1 after 100 cycles), significantly better than other carbon materials. The work provides a practical and significant reference to regulate precisely the surface energy storage active sites of coal based carbon material, aiming at advanced SIB and LIB.

Electrochemical reconstruction from mixed-phase nickel niobium to Ni-rich LixNb2O5 towards fast charging Li-ion battery

Fast charging capability is a crucial aspect of next-generation ion battery development, but the ion diffusion rate in existing anode materials is limited. It is necessary to design an anode material with a suitable host structure to effectively promote the ion transport rate. In this study, a novel nickel niobate (Ni4Nb2O9) is proposed as an anode material for lithium-ion battery, and a mixed-phase structure consisting of NiNb2O6 and Ni4Nb2O9 (M-NNO) is creatively constructed based on component engineering. The phase interfaces within the mix phases prove instrumental in facilitating the transmission of lithium ions and electrons. Notably, Ni-rich Ni4Nb2O9 enhances the precipitation of metallic Ni nanoparticles during electrochemical reconstruction, thereby effectively improving the electrical conductivity of the electrode material and enhancing its rate performance. The composite delivers an impressive specific capacity of 216 mAh g−1 at 1C and maintains 98.9 % capacity retention after 1000 cycles at 10C. Moreover, the assembled full-cell with NCM811 as a cathode exhibits 173.1 mAh‍ g−‍1 at current densities of 1C. Therefore, the mixed-phase nickel niobates demonstrate good adaptability and stability in a wide voltage range (0.005–3 V), presenting a new approach for designing high-performance and fast charging lithium battery anodes.

(Invited) Nickel Nanoparticles Modified Carbon Film Electrodes for Detection of Sugars

Metal nanoparticles such as Pt, Au, Ni and Cu have been employed to detect various analytes including hydrogen peroxide, alcohol and sugar. Among these metal nanoparticles, Ni and Cu nanoparticles show excellent electrocatalytic activity for oxidizing sugars in alkaline solution. We employed co-sputtering and plating technique to fabricate nanostructured electrodes for enhancing electrocatalytic activity for oxidation of sugars. First example is a metal hererodimer modified carbon film electrodes. The metal nanoparticles embedded carbon film electrodes was fabricated by unbalanced magnetron (UBM) sputtering and then plated different metal nanoparticles selectively only on the embedded metal nanoparticles by utilizing overpotential difference between carbon and metal nanoparticles surfaces. Using this technique, various combinations of metals are available to fabricate vertically oriented heterodimers embedded in the carbon films. In fact, we succeeded to fabricated Ni(upper)@Pd(lower), Pt@Pd, Au@Pd, Ni@Au, Pt@Au and Pd@Au heterodimers partially embedded in the carbon film. Among these heterodimers, Ni@Pd heterodimer embedded carbon film electrode shows much higher redox reaction of Ni(OH)2 covered on the Ni nanoparticles surface compared with that on the Ni nanoparticles without Pd. The NiOOH formed by electrochemical oxidation shows much higher electrocatalytic activity for glucose compared with that formed on Ni nanoparticles modified carbon film electrode. Also, the Ni@Pd heterodimers are mechanically very stable and most of the heterodimers remained on the surface after ultrasonication treatment because surface Ni nanoparticles attached strongly to Pd nanoparticles embedded in the carbon film. In contrast, almost all Ni nanoparticles deposited on pure carbon film were detached from carbon surface after ultrasonication. The second example is a nitrogen terminated carbon film modified with Ni nanoparticles by plating. Carbon films were fabricated by UBM or RF sputtering methods and then introduced nitrogen containing functional groups. Then Ni nanoparticles were deposited by plating. The supporting effect of a N-doped carbon film induced superior crystallinity in plated Ni@Ni(OH)2 nanoparticles, which was confirmed by HAADF-STEM-EDS. This realized a much higher regeneration rate of catalytic sites (NiOOH) , leading to higher oxidation current for maltopentaose, which is well known oligosaccharide. Also, the overpotential of maltopentaose oxidation decreased significantly due to the effect of the electrostatic interaction between Ni nanoparticles and maltopentaose in the alkaline solution at pH 12.7. We also studied dependence of nitrogen concentration in the carbon film on regeneration rate of NiOOH and glucose oxidation. Both regeneration rate and electrocatalytic current of glucose oxidation increased with increasing nitrogen concentration from 0 to 3.1 %. With optimized nitrogen concentration, we could measure glucose from 25 µM to 400 µM. The enhanced activity of Ni nanoparticles could be advantageous to develop enzyme free biosensor or fuel cells using organic compounds such as sugars and oligosaccharides.[1]S. Shiba, A. Koike, S. Takahashi, D. Kato, T. Kamata and O. Niwa, ACS Nano, 16, 10589-10599 (2022).[2] S. Shiba, S. Ohta, K. Ohtani, S. Takahashi, D. Kato and O. Niwa, RSC Advances, 11, 13311-13315 (2021).

Metal Ni nanoparticles in-situ anchored on CdS nanowires as effective cocatalyst for boosting the photocatalytic H2 production and degradation activity

Rapid recombination of photoinduced charge carriers and photoinstability greatly hinder the large-scale application of CdS photocatalysis. Herein, non-noble metal Ni nanoparticles (NPs) as highly efficient co-catalysts are evenly anchored onto the surface of CdS nanowires (NWs) via a facile freeze calcination method. As a result, the H2 production performance of the optimal Ni/CdS NWs under the filter (λ ≥ 420 nm) is about 80 times that of the bare CdS NWs, reaching 13,267.2 μmol h−1 g−1 and the apparent quantum efficiency (AQE) is 9.3%. Furthermore, Ni/CdS NWs photocatalysts have a surprising performance in the degradation of reactive red (RR2) and tetracycline hydrochloride (TCH), and the optimal photodegradation properties are 0.125 and 0.069 min−1, respectively. According to the experimental characterization and theoretical calculation analysis, the deposition of Ni NPs not only increases the active sites of the reaction but also restrains the recombination of photoinduced charge carriers, so ameliorating the photocatalytic performance of CdS photocatalysts. This work provides a novel standpoint for designing non-noble metal co-catalyst/semiconductor photocatalysts for efficient solar energy conversion.

Resistive switching behaviour of nickel nanoparticle-embedded naphthalene sulphonic acid-doped polyaniline nanocomposites

Hybrid nanocomposite (NC) materials comprising organic polymers and inorganic metal nanoparticles (NPs) with unique properties are popular for their advanced technological applications including resistive switching memory devices. Herein, NCs of 2-naphthalene sulphonic acid-doped polyaniline nanotubes (PANI-NSA NTs) and nickel nanoparticles (Ni NPs) were synthesized via a facile chemical synthesis procedure where metallic Ni NPs were embedded in/deposited onto the surface of PANI-NSA NTs by a simple reduction method. Different characterization methods revealed successful deposition of weak ferromagnetic Ni NPs onto the PANI-NSA matrix. The bipolar resistive switching behaviour of the as-synthesized PANI-NSA + Ni NCs was investigated under the application of voltage stress in a two-terminal sandwiched device configuration. The fabricated indium tin oxide/PANI-NSA + Ni/silver (ITO/PANI-NSA + Ni/Ag) device displays bipolar resistive switching properties having a memory window of ∼1.5 × 103, and switches effectively over 200 cycles. Ohmic conduction in the lower-voltage regime and the space-charge-limited Mott–Gurney current conduction model in the higher-voltage region were identified as major charge conduction mechanisms in the high resistive state of the device. On the other hand, in the entire low resistive state region the experimental data followed the Mott–Gurney conduction model.

Electroless deposited NiP-fabric electrodes for efficient water and urea electrolysis for hydrogen production at industrial scale

Herein, an advanced approach for transforming ordinary cotton-polyester fabric into a flexible and catalytic current collector is demonstrated for water and urea electrolysis for industrial-scale H2 production, addressing challenges in energy and environmental sustainability. A controlled electroless plating is adopted to deposit conducting metallic Ni-nanoparticles together with NixPy-catalytically active phase on an open macroporous framework of fabric. NiP-fabric electrodes exhibit exceptional hydrogen evolution reaction (HER) in alkaline, acidic, and in artificial Sea-water with overpotential values of 159 mV, 127 mV, and 94 mV at 10 mA/cm2 current density respectively. These electrodes also demonstrate the outstanding oxidation reaction for oxygen evolution and urea oxidation with the potential of just 1.509 V vs RHE (at 20 mA/cm2) and 1.312 V vs RHE (at 10 mA/cm2), with the in-situ formation of more active NiOOH species. A self-supported and macro-porous electrode configuration regulates the adsorption/desorption of intermediates species, enhanced charge and mass transport, and easier desorption of oxygen molecules. Finally, a two-electrode water and urea electrolyzer is constructed by NiP-fabric, which can deliver an H2-production at 100 mA/cm2 at a potential of 1.883 V and 1.611 V, respectively.

Effect of Ni loading onto Pt (Pt‐Ni/C) electrocatalysts for PEM fuel cell: A study of ORR activity, stability, and temperature effect

AbstractPt is a noble metal when alloyed with transition metals like Ni onto the carbon support, minimizes the cost and increases the oxygen reduction reaction (ORR) activity and stability of Pt‐Ni/C electrocatalyst in a low‐temperature proton exchange membrane (LTPEM) fuel cell. A simple sonochemical‐based synthesis of Pt‐Ni/C bimetallic nanoparticles is carried out through varying amounts of Ni and Pt precursors. The various combinations of Pt and Ni metal (50:50, 75:25, and 83:17) nanoparticles were uniformly distributed on a carbon support. The shifting of 2θ values to higher levels in XRD patterns confirmed the alloy formation between Pt and Ni. The carbon (60 wt. %) supported Pt and Ni (40 wt. %) electrocatalyst ink is coated on a carbon paper which acts as a gas diffusion layer (GDL). The electrocatalytic performance of Pt‐Ni/C was evaluated in the PEM fuel cell using an electrochemical test station. The best performance was observed with the Pt: Ni (83:17) coated electrocatalyst, which delivered 0.162 W/cm2 power at 0.45 V. Also, the PEM fuel cell performance was enhanced by increasing the single cell's operating temperature.

Surface-engineered carbon nanofibers enriched with metallic particles for effective bimetallic MOF formation toward hybrid supercapacitors

Metal-organic frameworks (MOFs) are commonly used as positive electrode materials in hybrid supercapacitors (HSCs) because of their high specific surface area, tunable pore structure, and battery-like charge-storage nature. However, the redox-mediated charge-storage mechanism in MOFs affects the rate capability and cycle stability. To address this problem, herein, bimetallic MOFs (NiCo MOFs) are successfully synthesized on surface-engineered carbon nanofibers (NiCo CNFs) enriched with metallic (Ni and Co) nanoparticles by a hydrothermal method and named NiCo MOF@NiCo CNF. In the NiCo MOF@NiCo CNF composites, the NiCo CNF can boost the electrochemical activity and simultaneously enhance the effective growth of NiCo MOF due to the presence of metal contents in the NiCo CNF, which act as nucleation points and further facilitate metal‑carbon and metal‑oxygen interactions at the surface of the NiCo CNF and NiCo MOF. The unique structure of NiCo MOF@NiCo CNF helps to improve the electrochemical performance, and the specific capacity is found to be 295.4 mA h g−1 (1063.4 C g−1) at 1 A g−1. The fabricated NiCo MOF@NiCo CNF//ZIF CNF HSC device depicts an energy density of 45.4 Wh kg−1 at a power density of 800 W kg−1 and cycle stability with a capacitance retention of 70 % after 4000 cycles, demonstrating that NiCo MOF@NiCo CNF composites are a promising electrode for supercapacitor applications. The engineered CNF surfaces with the required metallic contents can generate a unique engineered composite structure, by the effective interaction from the metal-based functional materials, to enhance the composite properties and charge-storage kinetics.