Ultrafine Ni Nanoparticles Research Articles

In-situ exsolved ultrafine Ni nanoparticles from CeZrNiO2 solid solution for efficient photothermal catalytic CO2 reduction by CH4

CO2 reduction by CH4 (CRM) to produce fuel is of great significance for solar energy storage and eliminating greenhouse gas. Herein, the catalyst of ultrafine Ni nanoparticles supported on CeZrNiO2 solid solution (Ni@CZNO) was synthesized by the sol-gel method. High yield of H2 and CO (58.0 and 69.8 ​mmol ​min−1 ​g−1) and excellent durability (50 ​h) were achieved by photothermal catalytic CRM merely under focused light irradiation. Structural characterization and DFT calculations reveal that CZNO has rich oxygen vacancies that can adsorb and activate CO2 to produce reactive oxygen species. Oxygen species are transferred to ultrafine Ni nanoparticles through the rich Ni-CZNO interface to accelerate carbon oxidation, thereby maintaining the excellent catalytic stability of the catalyst. Moreover, the experimental results reveal that light irradiation can not only enhance the photothermal catalytic CRM activity through photothermal conversion and molecular activation, but also improve the stability by increasing the concentration of oxygen vacancies and inhibiting CO disproportionation.

γ-irradiation induced ultrafine Ni nanoparticles supported on biomass-derived macroporous carbon for enhanced microwave absorption in the X-band

A series of ultrafine Ni nanoparticles (NPs) supported on biomass-derived macroporous carbon composites are conducted by γ-irradiation induced reduction method. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) characterization show that the obtained materials have abundant macroporous structure and the Ni NPs are evenly decorated on the surface of macroporous carbon. Both high irradiation doses and increasing Ni2+ contents favor the production of smaller dots. When the irradiation dose is 220 kGy and the C/Ni2+ mole ratio is 1:6, the average diameter of Ni NPs can reach 7.7 nm. Electromagnetic analyses indicate that the ultrafine Ni NPs have a positive effect on the magnetic loss ability, due to their strong natural ferromagnetic resonances. The obtained sample (CSC–Ni-3) exhibits the best microwave absorption performances among these composites, with the strongest reflection loss (RL) value of −70.2 dB at 10.8 GHz for the thickness of 2.3 mm, and the effective absorption band (EAB) in the X-band (8.2–12.4 GHz) is up to 3.2 GHz. The advantages of CSC-Ni-3 can be clearly established in both matched impedance and high magnetic loss ability. The γ-irradiation strategy presents a promising way for the design of ultrafine Ni NPs for high-performance microwave absorption.

Operating Lithium–Sulfur Batteries in an Ultrawide Temperature Range from ‒50 °C to 70 °C

AbstractLithium–sulfur (Li–S) batteries, boasting a high theoretical energy density, have garnered significant attention. However, their application across a wide temperature range remains hindered by the exacerbation of the polysulfide shuttle effect and sluggish reaction kinetics. Herein, this work designs a nanocomposite electrocatalyst consisting of Ni nanoparticles anchored onto carbon nanotubes (denoted as Ni@C/CNT) by directly carbonizing a metal‐organic framework/CNT (MOF/CNT) composite. This electrocatalyst is then coated onto a commercial separator, acting as a polysulfide trapper and kinetics accelerator for Li–S batteries. In this design, the Ni@C/CNT electrocatalyst features a uniform distribution of ultrafine Ni nanoparticles, derived from an MOF precursor with ordered metal sites, which facilitates polysulfide conversion at low temperature and chemisorption of polysulfides at high temperatures. Therefore, Ni@C/CNT‐modified cells can stably cycle across a wide temperature range, from ‒50 °C to 70 °C. They also demonstrate excellent performance with high‐sulfur loading (9.0 mg cm−2) at room temperature and exhibit an ultralow self‐discharge capacity attenuation of 2.59% after a 48‐h resting period. These promising results may guide the advanced design of Li–S batteries with broad operating‐temperature capabilities.

Exceptional activity of hollow porphyrin frameworks-confined Ni nanoparticles for hydrogen production from NaBH4 methanolysis

Hollow framework materials have recently attracted broad interest owing to the multifarious superiorities, such as large surface area, adjustable pore structure, short transport distance, as well as high permeability. Herein, a nitrogen-rich hollow porphyrin framework (H-POF) was synthesized via SiO2 as hard template. Then, ultrafine Ni nanoparticles (NPs) were confined on the surface of H-POF via ultrasonic impregnation reduction method. The resultant Ni/H-POF catalyst shows an extraordinary catalytic performance toward the methanolysis of NaBH4, providing a hydrogen generation rate (HGR) value of 34720 mL·min−1·gmetal−1, which surpasses all heterogeneous catalysts ever reported with NaOH. Further experimental investigation confirms that the high catalytic activity can attributed to the large specific surface area and hollow structure of the support, small size of metal NPs, as well as the electron-donating effect of nitrogen atoms on metal NPs. Based on isotopic experiments, the breaking of OH bond in CH3OH is proved to be the rate-determining step (RDS) of NaBH4 methanolysis. This work provides valuable insights for rationally designing nitrogen-rich hollow framework materials for supporting ultrafine metal NPs, which will be used for the future energy-related applications.

High-loading, ultrafine Ni nanoparticles dispersed on porous hollow carbon nanospheres for fast (de)hydrogenation kinetics of MgH2

Magnesium hydride (MgH2) is one of the most promising hydrogen storage materials for practical application due to its favorable reversibility, low cost and environmental benign; however, it suffers from high dehydrogenation temperature and slow sorption kinetics. Exploring proper catalysts with high and sustainable activity is extremely desired for substantially improving the hydrogen storage properties of MgH2. In this work, a composite catalyst with high-loading of ultrafine Ni nanoparticles (NPs) uniformly dispersed on porous hollow carbon nanospheres is developed, which shows superior catalytic activity towards the de-/hydrogenation of MgH2. With an addition of 5 wt% of the composite, which contains 90 wt% Ni NPs, the onset and peak dehydrogenation temperatures of MgH2 are lowered to 190 and 242 °C, respectively. 6.2 wt% H2 is rapidly released within 30 min at 250 °C. The amount of H2 that the dehydrogenation product can absorb at a low temperature of 150 °C in only 250 s is very close to the initial dehydrogenation value. A dehydrogenation capacity of 6.4 wt% remains after 50 cycles at a moderate cyclic regime, corresponding to a capacity retention of 94.1%. The Ni NPs are highly active, reacting with MgH2 and forming nanosized Mg2Ni/Mg2NiH4. They act as catalysts during hydrogen sorption cycling, and maintain a high dispersibility with the help of the dispersive role of the carbon substrate, leading to sustainably catalytic activity. The present work provides new insight into designing stable and highly active catalysts for promoting the (de)hydrogenation kinetics of MgH2.

H2 Plasma Reducing Ni Nanoparticles for Superior Catalysis on Hydrogen Sorption of MgH2

Highly fine, dispersive, and active catalysts are essential for lowering the operating temperature of MgH2, a promising high-capacity material for solid-state hydrogen storage. In this work, ultrafine Ni nanoparticles (2–6 nm) are synthesized from the precursor nickel acetylacetonate (C10H14NiO4) on the surface of MgH2 by H2 plasma reduction process, followed by further ball milling. The obtained composite could rapidly release more than 6.5 wt % H within 10 min at 275 °C. Even at a low temperature of 225 °C, up to 6 wt % H could be desorbed. The MgH2–Ni composite also exhibits excellent low-temperature hydrogenation kinetics and almost no capacity degradation over nine hydrogenation/dehydrogenation cycles. The significant improvement in the hydrogen-storage properties is attributed to the in situ formation of ultrafine and stable Mg2NiH0.3 nanocrystals during cycling. This work provides a convenient approach to synthesize ultrafine metal nanoparticles for catalytic applications in the field of high energy storage density hydride materials.

In situ formed ultrafine metallic Ni from nickel (II) acetylacetonate precursor to realize an exceptional hydrogen storage performance of MgH2[sbnd]Ni-EG nanocomposite

It has been well known that doping nano-scale catalysts can significantly improve both the kinetics and reversible hydrogen storage capacity of MgH2. However, so far it is still a challenge to directly synthesize ultrafine catalysts (e.g., < 5 nm), mainly because of the complicated chemical reaction processes. Here, a facile one-step high-energy ball milling process is developed to in situ form ultrafine Ni nanoparticles from the nickel acetylacetonate precursor in the MgH2 matrix. With the combined action of ultrafine metallic Ni and expanded graphite (EG), the formed MgH2Ni-EG nanocomposite with the optimized doping amounts of Ni and EG can still release 7.03 wt.% H2 within 8.5 min at 300 °C after 10 cycles. At a temperature close to room temperature (50 °C), it can also absorb 2.42 wt.% H2 within 1 h. It can be confirmed from the microstructural characterization analysis that the in situ formed ultrafine metallic Ni is transformed into Mg2Ni/Mg2NiH4 in the subsequent hydrogen absorption and desorption cycles. It is calculated that the dehydrogenation activation energy of the MgH2Ni-EG nanocomposite is also reduced obviously in comparison with the pure MgH2. Our work provides a methodology to significantly improve the hydrogen storage performance of MgH2 by combining the in situ formed and uniformly dispersed ultrafine metallic catalyst from the precursor and EG.

Boosting hydrogen evolution electrocatalysis through defect engineering: A strategy of heat and cool shock

Developing new strategy to further improve hydrogen evolution reaction (HER) performance of transition metal-based electrocatalysts is of high significance to accelerate commercial application of hydrogen energy. Here, HER activity is significantly enhanced through introducing crystal defects. The combined methods of heat and cool shock calcination, mask fiber templates as both reducing agent and carbon source were applied to synthesize microtube-like electrocatalysts composed of cross-linked carbon sheets and ultrafine Ni nanoparticles. The extensive active sites (edges, corners, steps, jaggies and strain) on the surface of Ni nanoparticles caused by grain surface, twin boundaries and stacking faults could synergically accelerate HER activity by optimizing adsorption capability of electrocatalysts and exposing atoms with high surface energy. Meanwhile, the defect-rich Ni nanoparticles wrapped by few-layer graphene are uniformly fixed on the conductive carbon network, which provides abundant diffusion channels for H2 and electrolyte, as well as effectively prevents Ni nanoparticles aggregation and avoids Ni grains being peeled off during long-term HER operation. As expected, the as-prepared electrocatalyst exhibits prominently improved electrocatalytic activity and admirable stability for HER. This work provides some innovatively technical insight in new-type catalysts development and defects engineering.

Metal organic framework derived Ni/CeO2 catalyst with highly dispersed ultra-fine Ni nanoparticles: Impregnation synthesis and the application in CO2 methanation

CO2 methanation is a promising strategy to convert the greenhouse gas into synthetic natural gas, which is known as a clean fuel with higher energy density. Ni/CeO2 is one of the active catalysts for CO2 methanation reaction. However, Ni/CeO2 with conventional metal/support structure suffers from the problem of nanocrystal coarsening during high-temperature reaction and thus decreasing catalytic activity. In this work, a Ni/CeO2 catalyst with novel structure was designed and synthesized through impregnation of Ce-based metal organic framework (MOF) with Ni precursor followed by calcination process. Due to the confinement effect of ultra-small pores derived from the MOF, Ni/CeO2 catalysts with ultrafine Ni nanoparticles, high dispersion and good thermostability were resulted. Among all the samples, Ni/CeO2 calcined at 600 °C showed the best catalytic performance due to the highest amount of oxygen vacancies. This work demonstrates a facile way to synthesize a broad range of ultra-fine metal/metal oxide nanocomposite catalysts with high catalytic activity and good stability for various applications.

Structured silicalite‐1 encapsulated Ni catalyst supported on SiC foam for dry reforming of methane

AbstractStructured silicalite‐1 zeolite encapsulated Ni catalyst supported on silicon carbide foam (i.e., Ni@S1‐SiC) was prepared using a new yet simple one‐pot method, showing the significantly improved anti‐sintering and anti‐coking performance in comparison with the conventional supported and encapsulated Ni catalysts (i.e., Ni/S1, Ni/S1‐SiC, and Ni@S1), in catalytic dry reforming of methane (DRM). The developed Ni0.08@S1‐SiC catalyst showed high CO2/CH4 conversions of &gt;85% and H2/CO molar ratio of &gt;0.85 at 700°C, outperforming other control catalysts under investigation. Additionally, the Ni0.08@S1‐SiC catalyst demonstrated high turnover frequency (TOF) values of ~5.6 and ~2.1/s regarding to CO2/CH4 conversions at 400°C, exhibiting excellent stability and low pressure‐drop during 100 hr on stream evaluation. Post‐reaction characterization of the used catalysts demonstrated that the combination of zeolite encapsulated Ni catalysts and SiC foam enabled well‐dispersed and ultrafine Ni nanoparticles, low pressure drop and intensified transfer steps, presented excellent anti‐sintering and anti‐coking abilities.

Ultrafine Ni nanoparticles anchored on carbon nanofibers as highly efficient bifunctional air electrodes for flexible solid-state zinc-air batteries

Development of well-designed bifunctional electrocatalysts with high activity for OER (oxygen evolution reaction) and ORR (oxygen reduction reaction) are a crucial topic owing to their promising applications in rechargeable Zinc (Zn)-air battery. Herein, a facile adsorption-pyrolyzation strategy is proposed for preparing ultrafine Ni nanoparticles anchored on carbon nanofiber (Ni/CNF), which derives from pyrolyzation of bacterial cellulose (BC) (with pre-adsorbed of Ni2+) via a two-step heat-treatment procedure (firstly 360 ℃, and then 750 ℃) (Ni/CNF-750) and used as an excellent oxygen electrocatalyst for flexible all solid-state Zn-air cell. The resultant ultrafine Ni/CNF-750 with plentiful pore structure and relatively high specific surface area of 449.0 m2 g−1, delivering overpotential of 293 mV at current density of 10 mA cm−2 for OER, obtaining an onset potential of 0.93 V vs. RHE and half-wave potential of 0.76 V vs. RHE for ORR. Moreover, a home-made flexible all solid-state battery is constructed by using Ni/CNF-750 as air electrodes, which provides a power density of 56.8 mW cm−2 and wonderful cycling durability with maintaining 50 cycles, and can drive a light-emitting-diode (LED) device. Our work may provides a reliable approach for fabricating ultrafine metal nanoparticles anchored on carbon based substrate with high activity for next-generation energy conversion and storage devices.

Sequential Electrodeposition of Bifunctional Catalytically Active Structures in MoO3 /Ni-NiO Composite Electrocatalysts for Selective Hydrogen and Oxygen Evolution.

Exploring earth-abundant and highly efficient electrocatalysts is critical for further development of water electrolyzer systems. Integrating bifunctional catalytically active sites into one multi-component might greatly improve the overall water-splitting performance. In this work, amorphous NiO nanosheets coupled with ultrafine Ni and MoO3 nanoparticles (MoO3 /Ni-NiO), which contains two heterostructures (i.e., Ni-NiO and MoO3 -NiO), is fabricated via a novel sequential electrodeposition strategy. The as-synthesized MoO3 /Ni-NiO composite exhibits superior electrocatalytic properties, affording low overpotentials of 62 mV at 10 mA cm-2 and 347 mV at 100 mA cm-2 for catalyzing the hydrogen and the oxygen evolution reaction (HER/OER), respectively. Moreover, the MoO3 /Ni-NiO hybrid enables the overall alkaline water-splitting at a low cell voltage of 1.55 V to achieve 10 mA cm-2 with outstanding catalytic durability, significantly outperforming the noble-metal catalysts and many materials previously reported. Experimental and theoretical investigations collectively demonstrate the generated Ni-NiO and MoO3 -NiO heterostructures significantly reduce the energetic barrier and act as catalytically active centers for selective HER and OER, synergistically accelerating the overall water-splitting process. This work helps to fundamentally understand the heterostructure-dependent mechanism, providing guidance for the rational design and oriented construction of hybrid nanomaterials for diverse catalytic processes.

The reconstruction of Ni particles on SBA-15 by thermal activation for dry reforming of methane with excellent resistant to carbon deposition

The improved Ni/SBA-15 catalysts were prepared by thermal inducing method and applied to dry reforming of methane. The promoting effect exerted by thermal activated reconstruction was studied systematically by means of various characterization techniques. TEM results indicated that the thermal inducing process led to the reconstruction of Ni particles to form ultra-fine Ni nanoparticles (2–3 nm) uniformly distributed on SBA-15. The resulting Ni nanoparticles not only improved catalytic activity but also inhibited the formation of carbon deposition during the DRM reaction. The thermal treatment catalyst with tiny particles presented the superior catalytic performance in the DRM reaction, where H2/CO ratio was close to 1 and no deactivation was discovered after continuous reaction at 750 °C for 50 h. Additionally, it was found that the metal-support interaction was strengthened observably after the thermal activated reconstruction. The strong interaction anchored Ni particles to prevent their high temperature sintering, thus forming stable catalytic centers. Therefore, the conversions of both CO2 and CH4 almost stabilized at 90% and 85%, respectively, for the thermal activated reconstruction samples during the long-term catalytic test.

Ultrathin Ni-MOF Nanobelts-Derived Composite for High Sensitive Detection of Nitrite.

In this paper, the Ni/NiO ultrathin nanobelts were successively synthesized by a facile in suit conversion process using pre-synthesized Ni-based metal-organic frameworks (MOFs) nanobelts as parent materials to detect the nitrite (NaNO2). The synthesized Ni/NiO composites have the advantages in structure, as follows: (I) Interleaved 3D reticulated structure has strong mechanical stability; (II) Ultrathin nanobelt structures allow more active sites to be exposed and make the transfer of charge faster; (III) A large number of ultrafine Ni nanoparticles decorate the building blocks of the NiO nanobelt and enhance the electrical conductivity. Ni/NiO/GCE has an obvious oxidation peak at 0.78 V, when the concentration is between 0.5 and 1000 μM, the oxidation peak current of NaNO2 is linearly related to the concentration, and the sensitivity is 1.5319 μA mM−1 cm−2 (S/N = 3). Moreover, the experimental results also concluded that the Ni/NiO ultrathin nanobelts not only indicated wonderful reproducibility in the determination of NaNO2 in the pickled pork samples, but also could be well-recovered and keep stable for a long time.

Nickel-Ceria Nanowires Embedded in Microporous Silica: Controllable Synthesis, Formation Mechanism, and Catalytic Applications.

Designing highly efficient catalysts for use in fuel production is a highly attractive research area but still remains challenging. Herein, for the first time, ultrafine Ni nanoparticles (NPs) self-assembled on ceria nanowires (NWs) and then embedded in a microporous silica shell (denoted as Ni-CeO2@SiO2) are successfully designed and synthesized via a one-pot facile strategy. The average diameter of Ni-CeO2 NWs is just 2.9 nm, and the length is up to 102.7 nm. The resulting Ni-CeO2@SiO2 exhibits high performance and 100% hydrogen selectivity for H2 production from N2H4 and N2H4BH3 in aqueous solution. Unexpectedly, Ni-CeO2@SiO2 also has good catalytic performance and thermal stability for CO2 methanation. The high catalytic performance of Ni-CeO2@SiO2 can be attributed to the synergistic electronic effect and strong interaction between Ni NPs and CeO2 NWs with plenty of oxygen vacancies, as well as the unique structure effect. As an effective strategy, the present work provides an opportunity to embed ultrafine metal NPs-CeO2 NWs into a microporous silica shell, which has broad application prospects in various catalytic fields.

Monolayer carbon-encapsulated Mo-doped Ni nanoparticles anchored on single-wall carbon nanotube film for total water splitting

Electrochemical water splitting is regarded as a sustainable and cost-effective route for the production of hydrogen. However, the high-cost and poor stability of traditional rare-earth metal-based electrocatalysts make it difficult to yield hydrogen economically. Here, we report an efficient and durable film electrocatalyst of N-doped monolayer carbon encapsulated Mo-doped ultrafine Ni nanoparticles anchored on single-wall carbon nanotube network (NMoNi/SWCNT) for total water splitting in an alkaline solution. The single layer carbon prevents oxidation of encapsulated Ni and Mo species and facilitates desired electronic structure modulation to achieve a high catalytic activity. Hence, the freestanding NMoNi/SWCNT film catalyst shows low overpotentials of 255 mV and 130 mV to attain a current density of 10 mA cm−2 for oxygen evolution reaction and hydrogen evolution reaction, respectively, with a good stability. More importantly, the NMoNi/SWCNT film only requires a potential of 1.6 V to reach a current density of 20 mA cm−2 when employed as both anode and cathode for a total water splitting.

Enhanced Coke Resistance and Antioxidation Stability of γ‐Alumina‐Supported Nickel‐Based Catalysts via Decoration with Lanthanum for Propane Pre‐Reforming

AbstractLa‐doped mesoporous γ‐alumina supported Ni oxides (xLa@NiO/γ‐MA) were prepared through one‐pot hydrolysis of inorganic salts, without the need for surfactants as in conventional practice. The catalysts were studied in the pre‐reforming of propane at a low steam to carbon molar ratio of 0.7. The results showed that the addition of La could promote the uniform dispersion of Ni species with reduced crystallite sizes, improving the catalytic properties. The 10La@Ni/γ‐MA catalyst (10 wt % La) exhibited the highest catalytic activity and excellent stability without carbon deposition for 150 hrs time‐on‐stream at 350 °C. This could be attributed to the presence of ultrafine Ni nanoparticles with an average metal particle size of 2.3 nm. Meanwhile, the doped La can donate electrons to the metallic Ni surface, preventing it from being oxidized. A minimum La/Ni atomic ratio of 1/11 (10 wt % La) was found to maintain the Ni antioxidation stability.

Highly dispersed ultrafine Ni particles embedded into MOF-74 arrays by partial carbonization for highly efficient hydrogen evolution

Here, we report the successful fabrication of highly dispersed ultrafine Ni nanoparticles (NPs) embraced into the partially carbonized Ni-MOF-74 (Ni NPs/C@Ni-MOF-74) microrod arrays by the heat treatment of the rod-like Ni-MOF-74 arrays grown on Ni foam.

One-pot synthesis of porous silica-supported ultrafine Ni nanoparticles as efficient and stable catalyst for selective hydrogenation of benzophenone

In this work, we report a silica-supported ultrafine Ni catalyst for the selective hydrogenation of benzophenone. This material was developed by a facile one-pot co-assembly syntheses strategy, using Ni(II) chelated alginate hydrogel as metal precursor and sacrificial template. Due to the highly active and uniformly dispersed Ni nanoparticles (NPs), 99.8% of benzophenone conversion was achieved. Remarkably, it also reached a 97.7% of selectivity for benzhydrol during benzophenone hydrogenation. Temperature-programmed desorption of ammonia (NH3-TPD) and Density Functional Theory (DFT) results reveal that the in-situ generated sodium carbonate (Na2CO3) derived from sodium alginate is essential in tuning the selectivity of benzhydrol: the existence of Na2CO3 reduces the surface acidity of catalyst and promotes the desorption of intermediate benzhydrol, preventing its further hydrogenolysis on the surface acidic sites of catalyst. Moreover, the supported Ni catalyst shows no significant loss of its activity during 20 times of recycling.

Biotemplate-Assisted Synthesis of Layered Double Oxides Confining Ultrafine Ni Nanoparticles as a Stable Catalyst for Phenol Hydrogenation

A confined Ni(0) nanocatalyst derived from NiAl-layered double hydroxide (NiAl-LDH), with ultrafine Ni nanoparticles implanted in the NixAlyO support, was first fabricated by the urea coprecipitation method using pine pollen as a biotemplate, together with subsequent calcination/reduction process. This hollow biotemplate-assisted catalyst displayed high phenol-hydrogenation activity and stability, which can be ascribed to its higher surface area, better dispersibility, and ultrafine Ni particle size. The hollow morphology and confinement effect of lamellar NiAl-LDH can not only lead to better dispersion of the active Ni(0) species, but also strengthen the interaction between Ni(0) species and NixAlyO support. This protocol can overcome the shortcomings of conventional LDH-derived catalysts that lack specifically shaped morphology and hierarchical structure, inhibiting the aggregation of the Ni nanoparticles, hence resulting in its good activity and stability.