Search Results (518)

Nickel–zinc batteries are promising candidates for safe, cost-effective, and high-power energy storage. However, the poor cycling stability of zinc anodes, mainly caused by dendrite growth and dissolution, remains a major challenge for their practical application. Herein, carbon-coated nano-ZnO (ZnO@C) composites were synthesized via a sol–gel method using polyvinyl alcohol (PVA) and zinc acetate as precursors. By systematically tuning the carbon content, the ZnO@C-6 sample with a carbon-to-ZnO mass ratio of 1:6 exhibited the best structural and electrochemical performance. Characterization confirmed a uniform amorphous carbon layer that enhanced conductivity and inhibited ZnO dissolution. Electrochemical tests demonstrated that ZnO@C-6 exhibited high reversible capacity (500 mAh g⁻¹ at 12 C after 1000 cycles), coulombic efficiency (>80%), and superior rate capability up to 30 C. Post-cycling SEM confirmed that the carbon coating effectively inhibits dendrite formation and preserves electrode morphology. These findings highlight the critical role of carbon coatings in stabilizing ZnO-based anodes and offer a viable pathway toward high-performance Ni-Zn batteries. Full article

The chromium-free oxide precursor strategy effectively avoids chromium volatilization and electrode contamination in metal-supported solid oxide fuel cells (MS-SOFCs), while enabling high-temperature co-sintering in air to simplify the fabrication process. However, the drastic microstructural coarsening, dimensional shrinkage, and thermal expansion mismatch with adjacent components of such substrates during high-temperature sintering, reduction, and thermal cycling collectively contribute to the interfacial instability and structural degradation of MS-SOFCs. Herein, we address these issues by incorporating a small amount of Gd_0.1Ce_0.9O_1.95 (GDC) to the NiO-Fe₂O₃ (NFO) substrate. The incorporation of GDC significantly enhances the sintering compatibility and reduction stability of the MS-SOFCs, alleviating the stress-induced warping and distortion. Moreover, the GDC phase has a pinning effect to suppressing the coarsening of the substrates during high-temperature sintering and reduction processes, enhancing mechanical integrity and structural robustness of the single cell. With 15 wt% GDC incorporated into the NiFe substrate, the corresponding MS-SOFC with GDC electrolyte film achieves a peak power density of 0.56 W cm⁻² at 600 °C, along with markedly improved structural integrity and operational reliability. This work demonstrates a viable pathway for designing heterophase-engineered supports with matched thermomechanical properties, offering promising prospects for enhancing the durability of MS-SOFCs. Full article

The reaction of the bulky ligand 1,2-bis-(di-tert-butylphosphinomethyl)benzene, 1 with [Ni(DME)Cl₂], 3, DME = 1,2-dimethoxyethane, at room temperature over extended periods, affords the new blue Zwitterionic complex [2-(C₆H₄-CH₂P(H)^tBu₂-1-(CH₂P^tBu₂NiCl₃)], 4, which contains a phosphonium group and an anionic nickel trichloride. This complex decomposes in alcohols such as methanol and the solution turns yellow. A discussion of the possible mechanism leading to the observed product is presented. Key to this is identification of the source of the phosphonium proton, which we speculated to arise from trace water in the initial nickel complex. To prove that trace water was present in [Ni(DME)Cl₂], a sample of this precursor was reacted under similar condition with anhydrous DMF alone. In addition to the known complex [Ni(DMF)₆)]²⁺[NiCl₄]²⁻, 5, we identified the trans-diaqua complex [Ni(Cl)₂(H₂O)₂(DMF)₂], 6, which proved the presence of trace water. Interestingly in dimethylformamide, [2-(C₆H₄-CH₂P(H)^tBu₂-1-(CH₂P^tBu₂NiCl₃)] exhibits thermochromic properties: an solution that is pale blue at ambient temperature reversibly changes colour to yellow upon cooling. This behaviour is specific to DMF and is related to the solvato-chromic behaviour exhibited by related DMF–nickel complexes. A discussion of the NMR spectra of compound 4 in a range of solvents is presented. The structures of the previously prepared molybdenum complex, [1,2-(C₆H₄-CH₂P^tBu₂)₂Mo(CO)₄] and the bis-(phosphine sulphide) of the ligand, [1,2-(C₆H₄-H₂P(S)^tBu₂)₂], 5, are described for structural comparative purposes. Full article

The study employed a green, template-free ball milling method to construct a series of Ni-Al mixed oxide catalysts modulated by different nickel precursors (nitrate, acetate, carbonate, sulfate, and chlorate). Through multiscale characterization techniques (XRD, TEM, XPS, H₂-TPR, etc.) and catalytic performance evaluations, we systematically elucidated the regulatory mechanism of precursor types on the structure-performance relationship. The NiAlO_x-CO₃²⁻ catalyst derived from nickel carbonate exhibited a unique structure, an optimal Ni/Al ratio, and well-tuned active oxygen species, thereby demonstrating exceptional catalytic performance in the oxidative dehydrogenation of ethane (ODHE) at 475 °C with 53.2% ethane conversion, 72.6% ethylene selectivity, and maintained stability over 40 h of continuous operation. Beyond developing high-performance ODHE catalysts, this work establishes a “precursor chemistry–material structure–catalytic performance” relationship model, offering new insights for the rational design of efficient catalysts for light alkane conversion. Full article

In this work, metal salts of phosphomolybdic acid were prepared and evaluated as catalysts in acetalization reactions of glycerol with furfural. These substrates have a renewable origin and play a crucial role in synthesizing bioadditives, which can enhance the physicochemical properties of fossil fuels and mitigate greenhouse gas emissions. Moreover, the biodiesel industry has generated a surplus of glycerol, and its use as a reactant is welcome from both economic and environmental viewpoints. Keggin heteropolyacid salts are less corrosive than traditional Brønsted acid catalysts and are easier to handle. Herein, metal phosphomolybdates were easily obtained from the acid precursor and metal chloride metathesis. A series of metal phosphomolybdates with the general formulae M₃[PMo₁₂O₄₀]_x n H₂O (M^x+ = Al³⁺, Fe³⁺, Co²⁺, Cu²⁺, Ni²⁺) was prepared and tested as catalysts in furfural glycerol acetalization reactions. Full article

With the rapid advancement of new energy electric vehicles, high-capacity nickel-rich layered oxides have emerged as predominant cathode materials in lithium-ion battery systems. However, their widespread implementation necessitates rigorous investigation into cycling stability. We synthesized nickel-manganese-aluminum hydroxide precursors as raw materials by co-precipitation method, and synthesized ultrathin Al₂O₃-coated LiNi_0.9Mn_0.05Al_0.05O₂ cathode materials by hydrolysis reaction. The cathode material was uniformly covered by an Al₂O₃ layer with an average thickness of 5–10 nm by high resolution transmission electron microscopy (HRTEM). Electrochemical performance tests showed that the modified cathode material exhibited significantly enhanced reversible capacity, cycling stability, and rate performance, and a more favorable differential capacity curve. In particular, the LNMA-2 samples were able to maintain 90.6% and 88.3% of their initial capacity after 100 cycle tests (with cutoff voltages of 4.3 and 4.5 V, respectively) at 0.5 C charge/discharge rate. These improved electrochemical properties are mainly attributed to the advantages offered by the unique Al₂O₃ coating structure. This study provides significant theoretical value for designing and optimizing the production of high-nickel cobalt-free cathode materials with high cycling performance. Full article

The complex system of high-entropy materials makes it challenging to reveal the specific function of each site for oxygen evolution reaction (OER). Here, with nickel foam (NF) as the substrate, FeCoNiCrMo/NF is designed to be prepared by metal–organic frameworks (MOF) as a precursor under an argon atmosphere. XRD analysis confirms that it retains a partial MOF crystal structure (characteristic peak at 2θ = 11.8°) with amorphous carbon (peaks at 22° and 48°). SEM-EDS mapping and XPS demonstrate uniform distribution of Fe, Co, Ni, Cr, and Mo with a molar ratio of 27:24:30:11:9. Electrochemical test results show that FeCoNiCrMo/NF has excellent OER characteristics compared with other reference prepared samples. FeCoNiCrMo/NF has an overpotential of 285 mV at 100 mA cm⁻² and performs continuously for 100 h without significant decline. The OER mechanism of FeCoNiCrMo/NF further reveal that Co and Ni are true active sites, and the dissolution of Cr and Mo promote the conversion of active sites into MOOH following the lattice oxygen mechanism (LOM). The precipitation–dissolution equilibrium of Fe also plays an important role in the OER process. The study of different reaction sites in complex systems points the way to designing efficient and robust catalysts. Full article

A facile and versatile strategy to obtain NPs@ZnAlO nanocomposite materials, comprising controlled-size nanoparticles (NPs) within a ZnAlO matrix is reported. The mono-(Au, Ni) and bimetallic (Ni-Au) NPs serving as an active phase were prepared by the polyol-alkaline method, while the ZnAlO support was obtained via the thermal decomposition of its corresponding layered double hydroxide (LDH) precursors. X-ray diffraction (XRD) patterns confirmed the successful fabrication of the nanocomposites, including the synthesis of the metallic NPs, the formation of LDH-like structure, and the subsequent transformation to ZnO phase upon LDH calcination. The obtained nanostructures confirmed the nanoplate-like morphology inherited from the original LDH precursors, which tended to aggregate after the addition of gold NPs. According to the UV-Vis spectroscopy, loading NPs onto the ZnAlO support enhanced the light absorption and reduced the band gap energy. ATR-DRIFT spectroscopy, H₂-TPR measurements, and XPS analysis provided information about the functional groups, surface composition, and reducibility of the materials. The catalytic performance of the developed nanostructures was evaluated by the photodegradation of bisphenol A (BPA), under simulated solar irradiation. The conversion of BPA over the bimetallic Ni-Au@ZnAlO reached up to 95% after 180 min of irradiation, exceeding the monometallic Ni@ZnAlO and Au@ZnAlO catalysts. Its enhanced activity was correlated with good dispersion of the bimetals, narrower band gap, and efficient charge carrier separation of the photo-induced e⁻/h⁺ pairs. Full article

Catalytic upgrading of pyrolysis oils is an important step for producing replacement hydrocarbon-rich liquid biofuels from biomass and can help to advance pyrolysis technology. Catalysts play a pivotal role in influencing the selectivity of chemical reactions leading to the formation of main compounds in the final upgraded liquid products. The present work involved a systematic study of solvent-free catalytic reactions of cyclohexanone in the presence of hydrogen gas at 160 °C for 3 h in a batch reactor. Cyclohexanone can be produced from biomass through the selective hydrogenation of lignin-derived phenolics. Three types of catalysts comprising undoped NbOPO₄, 10 wt% NiO/NbOPO₄, and 30 wt% NiO/NbOPO₄ were studied. Undoped NbOPO₄ promoted both aldol condensation and the dehydration of cyclohexanol, producing fused ring aromatic hydrocarbons and hard char. With 30 wt% NiO/NbOPO₄, extensive competitive hydrogenation of cyclohexanone to cyclohexanol was observed, along with the formation of C₆ cyclic hydrocarbons. When compared to NbOPO₄ and 30 wt% NiO/NbOPO₄, the use of 10 wt% NiO/NbOPO₄ produced superior selectivity towards bi-cycloalkanones (i.e., C₁₂) at cyclohexanone conversion of 66.8 ± 1.82%. Overall, the 10 wt% NiO/NbOPO₄ catalyst exhibited the best performance towards the production of precursor compounds that can be further hydrodeoxygenated into energy-dense aviation fuel hydrocarbons. Hence, the presence and loading of NiO was able to tune the activity and selectivity of NbOPO₄, thereby influencing the final products obtained from the same cyclohexanone feedstock. This study underscores the potential of lignin-derived pyrolysis oils as important renewable feedstocks for producing replacement hydrocarbon solvents or feedstocks and high-density sustainable liquid hydrocarbon fuels via sequential and selective catalytic upgrading. Full article

As the global energy industry shifts away from fossil fuels, there is a growing need for sustainable and renewable hydrogen production methods. This research investigates the potential of using biochar derived from animal waste as a precursor for creating effective catalysts for the hydrogen evolution reaction (HER). By incorporating copper and nickel into the biochar through hydrothermal processing, the study examined the resulting catalysts’ structural, chemical, and catalytic properties. Techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful integration of metallic nanoparticles and revealed notable changes in surface morphology, elemental composition, and functional group distribution. The Cu–Ni co-doped biochar catalyst (Cu–Ni/BC) demonstrated a significant 45% increase in hydrogen evolution efficiency compared to the undoped biochar control sample. These results highlight the synergistic effects of copper and nickel in enhancing the catalyst’s electron transfer capabilities and active site availability. This study offers a sustainable, cost-effective, and environmentally friendly alternative to conventional hydrogen production catalysts, presenting considerable potential for waste valorization while promoting clean energy solutions. The research aligns with circular economy principles, contributing to the advancement of sustainable energy technologies. Full article

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

With the continuous consumption of fossil energy and the related environmental problems, clean energy, especially the hydrogen energy-derived water electrolysis, has attracted wide attention. However, as a result of the high energy consumption of water electrolysis and the limitations of single-function catalysts, there is an urgent need for cheap and simple-to-make bifunctional catalysts. In this work, based on the NiFe-LDH that is usually used for OER (Oxygen Evolution Reaction), doping of heteroatoms was carried out and a bifunctional catalyst could be then prepared using biomass as the carbon source. The preparation of catalyst precursors and in situ reduction were performed through the coupling process of hydrothermal and pyrolysis to enhance the electrolytic activity of the catalyst. Results showed that the overpotentials required to reach a current density of 10 mA·cm⁻² for the HER and OER processes were 305.2 mV and 310.4 mV, respectively, which are superior to the commercial catalysts. In the subsequent characterization, the structural characteristics of the catalyst support and their structure–activity correlation with active metals were systematically investigated by TEM, XRD, and XPS analysis, providing mechanistic insights into the catalytic behavior. The basic catalytic mechanisms of HER and OER were also obtained: the HER process was due to the formation of a Ni₃Fe alloy structure during catalyst preparation, which changed the electronic structure of the catalyst, while the OER process was induced by the formation of a NiOOH intermediate. The research results are expected to provide new ideas and data support for the preparation of bifunctional catalysts. Full article

Co-axial electrospinning is one of the facile methods for the fabrication of core–shell metal oxides for environmental applications. Indeed, core–shell architectures featuring a magnetic core and a photocatalytic shell represent a novel approach to catalytic nanostructures in applications such as water treatment and pollutant removal via magnetic separation. This study focuses on the fabrication of novel Fe₃O₄-Fe₂NiO₄/NiO core–shell nanofibers with enhanced optical and magnetic properties using co-axial electrospinning. The aim is to optimize the fabrication parameters, particularly the amount of metal precursor in the starting solutions, to achieve well-defined core and shell structures (rather than single-phase spinels), and to investigate phase transitions, structural characteristics, as well as the optical and magnetic properties of the resulting nanofibers. Raman, XRD, and XPS results show several phases and high defect concentration in the NiO shell. The Fe₃O₄-Fe₂NiO₄/NiO core–shell nanofibers exhibit strong visible-light absorption and significant magnetization. These advanced properties highlight their potential in photocatalytic applications. Full article

With the continuous advancement of electromagnetic protection technologies, the development of lightweight electromagnetic wave-absorbing materials with excellent absorption performance has become a critical challenge in the field. In this study, commercially available hollow glass microspheres (HGMs) were employed as templates, and Ni²⁺/Co²⁺ metal ions were used to catalyze the polymerization of dopamine (PDA), forming HGM@Ni_xCo_y/PDA precursors. Subsequent high-temperature pyrolysis yielded lightweight composite absorbing materials, denoted as HGM@Ni_xCo_y/C. This material integrates dielectric loss, conductive loss, magnetic loss, and resonance absorption mechanisms, exhibiting outstanding electromagnetic wave absorption properties. The absorption performance can be effectively tuned by adjusting the Ni-to-Co ratio, with the optimal performance observed at an atomic ratio of 2:3. At a filler loading of 20 wt.%, HGM@Ni₂Co₃/C achieved an effective absorption bandwidth (EAB) of 6.83 GHz (ranging from 10.53 to 17.36 GHz) and a minimum reflection loss (RL_min) of −27.26 dB. These results demonstrate that the synergistic combination of hollow glass bubbles and carbon-based magnetic components not only significantly reduces the material density and required filler content but also enhances overall absorption performance, highlighting its great potential in the development of lightweight and high-efficiency electromagnetic wave absorbers. Full article

Complex antimony pyrochlores Bi_2.7M_0.46Ni_0.70Sb₂O_10+Δ (M = Zn, Mg) were synthesized from oxide precursors, using the solid-state reaction method. For each composition variant, the pyrochlore phase formation process was studied during solid-state synthesis in the range of 500–1050 °C. The influence of zinc and magnesium on the phase formation process was established. The interaction of oxide precursors occurs at a temperature of 600 °C and higher, resulting in the formation of bismuth stibate (Bi₃SbO₇) as a binary impurity phase. Oxide precursors, including bismuth(III) and antimony(III,V) oxides, are fixed in the samples up to 750 °C, at which point the intermediate cubic phase Bi₃M_2/3Sb_7/3O₁₁ (sp. gr. Pn-3, M = Zn, Ni) is formed in the zinc system. Interacting with transition element oxides, it is transformed into pyrochlore. An intermediate phase with the Bi_4.66Ca_1.09VO_10.5 structure (sp. gr. Pnnm) was found in the magnesium system. The unit cell parameter of pyrochlore for two samples has a minimum value at 800 °C, which is associated with the onset of high-temperature synthesis of pyrochlore. The synthesis of phase-pure pyrochlores is confirmed by high-resolution Raman spectroscopy. The data interpretation showed that the cations in Ni/Zn pyrochlore are more likely to be incorporated into bismuth positions than in Ni/Mg pyrochlore. The nickel–magnesium pyrochlore is characterized by a low-porosity microstructure, with grain sizes of up to 3 μm, according to SEM data. Zinc oxide has a sintering effect on ceramics. Therefore, the grain size in ceramics is large and varies from 2 to 7 μm. Full article