NiO Interface Research Articles

Selective atomic sieving across metal/oxide interface for super-oxidation resistance

Surface passivation, a desirable natural consequence during initial oxidation of alloys, is the foundation for functioning of corrosion and oxidation resistant alloys ranging from industrial stainless steel to kitchen utensils. This initial oxidation has been long perceived to vary with crystal facet, however, the underlying mechanism remains elusive. Here, using in situ environmental transmission electron microscopy, we gain atomic details on crystal facet dependent initial oxidation behavior in a model Ni-5Cr alloy. We find the (001) surface shows higher initial oxidation resistance as compared to the (111) surface. We reveal the crystal facet dependent oxidation is related to an interfacial atomic sieving effect, wherein the oxide/metal interface selectively promotes diffusion of certain atomic species. Density functional theory calculations rationalize the oxygen diffusion across Ni(111)/NiO(111) interface, as contrasted with Ni(001)/NiO(111), is enhanced. We unveil that crystal facet with initial fast oxidation rate could conversely switch to a slow steady state oxidation.

Anchoring magic NiCo2O4/NiO on Ni foam as an effective and binder-free electrocatalyst for boosting hydrogen evolution reaction

Electrocatalysts that can sustain water splitting without corrosion are required for large-scale water electrolysis applications. Thus, designing and constructing stable electrocatalysts is known as a crucial role in hydrogen evolution reactions (HER). Herein, NiCo2O4/NiO nanocubes on Ni foam (NF) as a stable electrocatalyst were fabricated successfully by using a facile hydrothermal method. Field Emission Scanning Electron Microscopy (FESEM) confirms the formation of distinct magic NiCo2O4/NiO/NF nanocubes with a size of 50–150 nm. The electrochemical tests indicated that the NiCo2O4/NiO nanocubes possess long stability of about 140 h and exceptional HER activity with a low overpotential of 38 mV at a current density of 10 mA.cm−2 in a 1 M potassium hydroxide (KOH) and a Tafel slope of only 45 mV.dec−1. The obtained results indicated that this level of HER catalytic performance is assigned to the rough surface and synergistic interactions between Ni and Co atoms in the nanocubes. It was also determined that the existence of NiO interface layer causes robust adhesion between NF and NiCo2O4 nanocubes. In addition, this discovery points to an advantageous future for the configuration and synthesis of highly effective, non-precious metal-based electrocatalysts for large-scale hydrogen production via water-splitting.

Design of highly active meso-zeolite enveloping Pt–Ni bimetallic catalysts for degradation of toluene

Degrading volatile organic compounds at low temperatures and active sites aggregation are still challenging. In this study, a novel mesoporous zeolite silicalite-1 (S-1-meso) enveloped Pt–Ni bimetallic catalysts (noted as Pt1Ni1@S-1-meso) were synthesized via a facile in situ mesoporous template-free method. The Pt–Ni bimetallic nanoparticles were uniformly distributed and displayed a large specific surface area and enriched mesopores to facilitate the deep oxidation of toluene. The presence of the Pt–NiO interface both increased the dispersion of the catalyst and improved its catalytic performance, thereby reducing the consumption of Pt. The Mars-van Krevelen mechanism and density function theory (DFT) calculations revealed that the Pt–NiO interface effect changed the electronic structure of Pt and Ni species, reduced the activation potential for oxygen, formed reactive oxygen species, and facilitated the adsorption and activation of reactants in the direction favorable to the toluene oxidation. This study provides a guideline for minimizing the proportion of precious metals used in practical applications and a promising method for toluene elimination at low temperatures.

Construction of ultrastable and high-rate performance zinc anode with three-dimensional porous structure and Schottky contact

The artificial interface layer on the Zn anode can effectively suppress by-product formation and dendrite growth, playing a crucial role in achieving high-rate and long-life aqueous zinc-ion batteries. However, the current galvanizing mode, where plating occurs separately below or inside the interface layer after its introduction, poses risks of detachment or swelling during cycling, limiting practical applications. In this study, we fabricate a three-dimensional porous NiO interface layer with enhanced anode dynamics that forms a Schottky contact with the zinc substrate. Through the synergistic effect of this excellent structure and Schottky barrier, zinc is rapidly and uniformly plated both inside and below the interface layer simultaneously. Symmetrical cells based on NiO@Zn exhibit exceptional stability over 10,000 cycles at an ultrahigh current density of 20 mA cm−2. Furthermore, NiO@Zn||MnO2 full cells deliver a capacity of 228 mAh g−1 and retain 94% of their initial capacities for 500 cycles at a density of 1 A g−1. This work not only presents highly reversible zinc anodes but also proposes an innovative galvanizing model.

MoNi4–NiO heterojunction encapsulated in lignin-derived carbon for efficient hydrogen evolution reaction

Molybdenum nickel alloy has been proved to be an efficient noble-metal-free catalyst for hydrogen evolution reaction (HER) in alkaline medium, but its electrocatalytic activity and stability need to be further improved to meet industrial requirements. In this study, carboxymethylated enzymatic hydrolysis lignin (EHL) was used as a biomacromolecule frame to coordinate with transition metal ions and reduced by pyrolysis to obtain the MoNi4–NiO heterojunction (MoNi4–NiO/C). The oblate sphere structure of MoNi4–NiO/C exposed a large catalytic active surface to the electrolyte. As a result, the hydrogen evolution reaction of MoNi4–NiO/C displayed a low overpotentials of 41 mV to achieve 10 mA cm−2 and excellent stability of 100 h at 100 mA cm−2 in 1 mol L−1 KOH, which was superior to that of commercial Pt/C. Lignin assisted the formation of NiO to construct the MoNi4–NiO interface and MoNi4–NiO heterojunction structure, which reduced the energy barrier by forming a more favorable transition states and then promoted the formation of adsorbed hydrogen at the heterojunction interface through water dissociation in alkaline media, leading to the rapid reaction kinetics. This work provided an effective strategy for improving the electrocatalytic performance of noble-metal-free electrocatalysts encapsulated by lignin-derived carbon.

Photoelectrochemical Hydrogen Evolution Using Dye-Sensitised Nickel Oxide

Photoelectrocatalysis offers a way to generate hydrogen and oxygen from water under ambient light. Here, a series of hydrogen evolving photocatalysts based on a ruthenium(II) bipyridyl sensitiser covalently linked to platinum or palladium catalytic centres were adsorbed onto mesoporous nickel oxide and tested for hydrogen evolution in a photoelectrochemical half-cell. The electrolyte buffer was varied and certain catalysts performed better at pH 7 than pH 3 (for example, PC3 with photocurrent density = 8 μA cm–2), which is encouraging for coupling with an oxygen evolving photoanode in tandem water splitting devices. The molecular catalysts were surprisingly robust when integrated into devices, but the overall performance appears to be limited by rapid recombination at the photocatalyst|NiO interface. Our findings provide further insight towards basic design principles for hydrogen evolving photoelectrochemical systems and guidelines for further development.

Highly efficient and simultaneous catalytic reduction of multiple toxic dyes and nitrophenols waste water using highly active bimetallic PdO\u2013NiO nanocomposite

Azo dyes and nitrophenols have been widely used in the various industry which are highly toxic and affecting the photosynthetic cycle of aquatic organism. The industry disposals increase the accumulation of azo compounds in the environment. In the present study, we synthesized the low cost, PdO-doped NiO hetero-mixture via simple hydrothermal combined calcination process. The morphology results proved that, the spherical PdO nanoparticles are evenly doped with NiO nanoparticles. The band gap values of metal oxides NiO, PdO and PdO–NiO composite were found to be 4.05 eV, 3.84 eV and 4.24 eV, respectively. The high optical bandgap (Eg) value for composite suggests that the PdO interface and NiO interface are closely combined in the composite. The catalytic activity of the PdO–NiO was analyzed for the reduction of different toxic azo compounds namely, 4-nitrophenol (NP), 2,4-dinitrophenol (DNP), 2,4,6-trinitrophenol (TNP), methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) separately and their mixture with the presence of a NaBH4. For the first time, the large volume of the toxic azo compounds was reduced into non-toxic compounds with high reduction rate. The proposed PdO–NiO catalyst exhibit excellent rate constant 0.1667, 0.0997, 0.0686 min−1 for NP, DNP and TNT and 0.099, 0.0416 and 0.0896 min−1 for MB, RhB and MO dyes respectively which is higher rate constant than the previously reported catalysts. Mainly, PdO–NiO completes the reduction of mixture of azo compounds within 8 min. Further, PdO–NiO exhibit stable reduction rate of azo compounds over five cycles with no significant loss. Hence, the proposed low cost and high efficient PdO–NiO catalyst could be the promising catalyst for degradation of azo compounds.

Atomic Heterointerface Boosts the Catalytic Activity toward Oxygen Reduction/Evolution Reaction

AbstractInterface engineering is an efficient strategy to enhance the electrocatalytic activity of hybrid materials by taking advantage of the synergistic effect of double or even multiple active sites. Here, the rational design of a Pd/NiO atomic interface with well patterned Pd arrays imbedded into NiO thin films are reported to boost the catalytic activity toward the oxygen reduction/evolution reaction. Theoretical analysis elucidates that the Pd (111)/NiO (111) interface with minimized lattice mismatch effectively adsorbs intermediates (OH*, LiO2*, Li2O2*, and Li2O*) and induces the growth/decomposition of electrochemical reaction products, which greatly lowers the Gibbs energy barrier of crucial steps and boosts the reaction kinetics. As expected, such hybrid thin films exhibit high catalytic activity for both the oxygen reduction reaction and oxygen evolution reaction, with performance comparable to the benchmarked Pt/C and RuO2 catalysts. Moreover, favorable performance is also achieved in both aqueous Zn–air batteries and aprotic Li–air batteries with an overpotential of only 0.69 and 0.50 V, respectively. This work suggests the great potential of such particularly morphological hybrid thin films in the development of high‐performance catalysts for energy storage and conversion.

Synergistic effects of α-Fe2O3 nanoparticles and Fe-doping on gas-sensing performance of NiO nanowires and interface mechanism

High surface area nickel oxide nanowires (NiO NWs), Fe-doped NiO NWs and α-Fe2O3/Fe-doped NiO NWs were synthesized with nanocasting pathway, and then the morphology, microstructure and components of all samples were characterized with XRD, TEM, EDS, UV–vis spectra and nitrogen adsorption–desorption isotherms. Owing to the uniform mesoporous template, all samples with the same diameter exhibit the similar mesoporous-structures. The loaded α-Fe2O3 nanoparticles should exist in mesoporous channels between Fe-doped NiO NWs to form heterogeneous contact at the interface of n-type α-Fe2O3 nanoparticles and p-type NiO NWs. The gas-sensing results indicate that Fe-dopant and α-Fe2O3-loading both improve the gas-sensing performance of NiO NWs sensors. α-Fe2O3/Fe-doped NiO NWs sensors presented the highest response to 100 ppm ethanol gas (55.264) compared with Fe-doped NiO NWs (24.617) and NiO NWs sensors (3.189). The donor Fe-dopant increases the ground state resistance and the absorbed oxygen content in air. α-Fe2O3 nanoparticles in electron depletion region result in the increasing resistance in ethanol gas and decreasing resistance in air. In this way, α-Fe2O3/Fe-doped NiO NWs sensor presents the excellent gas-sensing performance due to the formation of heterogeneous contact at the interface.

High performance acetaldehyde gas sensor based on p-n heterojunction interface of NiO nanosheets and WO3 nanorods

P-N heterojunction based chemi-resistive sensor is designed by incorporating NiO nanosheets (NSs) into WO3 nanorods (NRs) with high aspect ratio. The nanostructured NiO and WO3 were synthesized by facile hydrothermal chemical route and well-characterized by using XRD, FESEM, EDS, XPS, Raman, and elemental mapping. These two materials mixed in different weight ratio viz 5:95, 15:85, and 25:75 to fabricate the sensors named NW1, NW2, and NW3, respectively. The fabricated sensors were investigated for gas sensing properties at different operating temperatures. All the sensors revealed a high response towards acetaldehyde among various gases at 250 °C. Among these sensors, NW2 exhibited the highest response of 2184 % for 100 ppm acetaldehyde concentration at 250 °C and revealed a high response for 20–100 ppm acetaldehyde range. The NW2 sensor also showed excellent transient resistance response for different concentrations of acetaldehyde gas in real-time. The consistent response of the NW2 sensor for 100 ppm acetaldehyde was dynamically observed and confirmed remarkable repeatability in real-time. The high response and selectivity of the NW2 sensor are due to the p-n heterojunction formed at NiO and WO3 interface. The hypothesized acetaldehyde sensing mechanism was explored and the stability of the NW2 sensor was tested. This p-n heterojunction-based nanostructure can be promising to design high-performance acetaldehyde sensing application.

Construction of electron and grain boundary barrier in quantum dots light-emitting diodes: The role of NiO interface coating

NiO nanocrystals (NCs) thin film is applied as an electron barrier layer (EBL) for red quantum dot light-emitting diodes (QLEDs) to decrease the leakage current and balance the carrier transportation. The optimized NiO-based QLED exhibits the external quantum efficiency (EQE) of 5.85%, current efficiency (CE) of 6.9 cd A−1, with a maximum luminance of 31772 cd m−2, demonstrating that NiO is an effective EBL for QLEDs. The electron barrier height of 0.031 eV can effectively block 70% electron transport thanks to form the electron trap, grain boundary and depletion layer. The mechanism of the electron transport through NiO EBL is quantum tunneling, which is consistent to Richardson Schottky thermal injection model.

Multishelled NiO/NiCo2O4 hollow microspheres derived from bimetal-organic frameworks as high-performance sensing material for acetone detection

Recently, tremendous research interest was stimulated to obtain advanced function materials with hierarchical structure and tailored chemical composition from metal-organic frameworks (MOFs) based precursors. Herein, Bimetal-organic frameworks of Ni-Co-BTC solid microspheres synthesized through hydrothermal method were acted as template to induce multishelled NiO/NiCo2O4 hollow microspheres by annealing treatment. When evaluated as gas sensing material, the optimal hybrid of NiO/NiCo2O4 (the molar ration of NiCo=1.5) multishelled hollow microspheres endowed a high sensitivity (17.86) to 100 ppm acetone with rapid response/recovery time (11/13 s) under low working temperature (160 °C) and the low detection limit reached 25 ppb. The enhanced mechanism was originated from the following aspects: the multishelled hollow architecture provided efficient diffusion path for gas molecules and sufficient active site for gas sensing reaction; the nanoscale p-p heterojunction created at NiO and NiCo2O4 nanoparticles interface amplified the resistance variation by tuning the potential barrier; the potent combination of the “chemical catalytic” effect of NiO and the “electrical catalytic” effect of NiCo2O4 improved the selective acetone detection.

Effect of NiO interface coating on thermal and mechanical properties in Ba<sub>0.8</sub>Sr<sub>0.2</sub>TiO<sub>3</sub>/Cu matrix composites

Ba0.8Sr0.2TiO3 (BST) particles are an effective reinforcement to reduce the coefficient of thermal expansion of Cu composites because of their negative thermal expansion behavior during phase transformation. However, improving interface bonding is still the key point to further study. In this study, NiO interface coating is employed in the BST/Cu composite to improve interface bonding. NiO interface coating of the composite broadens the phase transformation temperature range of BST particles. Accordingly, the average thermal expansion of the composite in the temperature range of 30–250°C is reduced from 12.99×10−6 to 11.71×10−6 °C−1. In addition, the mechanical properties of the composite are considerably enhanced. In specific, the yield strength and the compressive strength are increased by 72.8% and 41.3%, respectively. This work verifies that NiO interface coating can effectively improve the interface bonding in the BST/Cu composite and further enhance the properties of the composite. The results imply that the NiO-BST/Cu composite has great potential for application in the future.

Effect of the Ni and NiO Interface Layer on the Energy Performance of Core/Shell CuO/Al Systems.

The interface layer is responsible for the outward migration of oxygen atoms, which subsequently leads to an adjustment in the energetic performance of nanothermite films. In this study, sandwich-structured CuO@Ni/Al and CuO@NiO/Al nanowire thermite films were successfully prepared to investigate the effects of the interface layer on the heat-release, ignition, and combustion performance. The effects of the Ni and NiO interface layers are extremely different on the heat-release performance and combustion properties of the CuO/Al nanowire thermite film. Herein, the introduced Ni layer decreased the heat release (1979.7 J/g), reactivity (Ea = 177.3 kJ/mol), and maximum pressure (2.32 MPa) compared with the CuO/Al composite. Al/Ni alloys can be formed at the interface to prevent oxygen from diffusing between CuO and Al. Moreover, the incorporation of the Ni interface layer into the CuO/Al systems results in a heat drop due to its heat-absorption capability as well as its blockage of heat transfer from the thermite reaction. The deposition of the NiO layer between CuO and Al leads to an increase in the heat release (3014.2 J/g) and a decrease in the activation energy (Ea = 178.6 kJ/mol). The NiO layer endows the CuO/Al system with a high energy-release rate and chemical reactivity. NiO can participate in a thermite reaction, which promotes the reaction of CuO/Al and induces the condensed phase.

Highly stable perovskite solar cells based on perovskite/NiO-graphene composites and NiO interface with 25.9 mA/cm2 photocurrent density and 20.8% efficiency

Perovskite solar cells (PSCs) demonstrated a record-high power conversion efficiency, but they have instability issues attributed to the degradation of materials and device performance. To overcome the instability problem and performance degradation, various methods have been proposed, but still need a comprehensive solution. Here, we propose an innovative way of insuring device performance and long-term stability by utilizing functional composites of perovskite, nickle oxide and graphene into device structures. We fabricated the PSCs based on MAPbI 3−x Cl x /NiO-graphene photoactive composite and NiO interface layer. Compared to the pristine perovskite cells, the champion device based on the photoactive composites with NiO interface showed remarkably high photocurrent density of 25.9 mA/cm 2 (i.e., 95.2% of theoretical maximum) and power conversion efficiency of 20.8% without J-V hysteresis. More impressively, unencapsulated cells showed significant improvement of thermal- and photo- and long-term air-stability with retaining 97–100% of the initial values of performance parameters over 310 days under ambient conditions. Schematic illustration of a perovskite solar cell structure based on MAPbI 3−x Cl x /NiO-rGO composite photoactive layer and NiO interface formed on the SrTiO 3 /Al 2 O 3 -graphene electron transfer layer, exhibiting the mechanism of charge carrier separation and conduction through graphene and connected NiO nanoparticles and blocking moisture and oxygen infiltration. • Highly stable and efficient composites-based perovskite solar cells. • Perovskite/NiO-graphene photoactive composite and NiO interface layer. • Remarkably high photocurrent density and power conversion efficiency without J-V hysteresis. • Significant improvement of thermal- and photo- and air-stability with retaining 97–100% of device performance over 310 days.

Aerobic oxidation of cyclohexane over metal-organic framework-derived Ce, Ni-modified Co3O4

The heterogeneous interface in materials, due to its crucial role in catalytic reactions, has attracted much attention. Herein, we report the facile synthesis of Co3O4 and Ce/Ni-modified Co3O4 catalysts derived from ZIF-67 and their application in the aerobic oxidation of cyclohexane. The catalytic performance of the catalysts was greatly affected by the calcination temperature and molar ratio of the second metal (Ce, Ni) to Co. The catalytic performance of Co3O4 improved with the increase of the calcination temperature and reached a plateau at 400 °C due to the small-sized Co3O4 crystallites and developed pore structures. The introduction of the second metal improved the dispersion of Co3O4 and induced the creation of the oxygen vacancies at Co3O4-CeO2/NiO interface. The highest catalytic activity with 12.8% conversion and 95.5% selectivity were achieved over the Ce-Ni-modified Co3O4 catalyst with the molar ratio of Ce/Ni/Co=0.11/0.21/1.00. The superior catalytic performance of the Ce-Ni-modified catalyst can be ascribed to the highly dispersed Co3O4 crystallites and the activation of the oxygen molecules by the oxygen vacancies.

Hierarchical WO3–NiO microflower for high sensitivity detection of SF6 decomposition byproduct H2S

In this work, hierarchical WO3–NiO microflowers have been designed and prepared through a controllable hydrothermal route for high sensitivity detection of H2S produced by SF6 decomposition. The hierarchical flower-like nanostructures assembled with numerous nanosheets were influenced by the introduction of WO3, which is regarded as a significant strategy for improving the gas sensing properties. The synthesized nanostructures were tested by various characterization to investigate the different microstructures of the nanocomposites. The H2S sensing performances of the sensors fabricated with these flower-like nanostructures were measured, which indicated that 3.0 at% WO3–NiO microflower based sensor possessed excellent properties such as higher gas responses and more prominent repeatability compared with those of other fabricated sensors. The enhanced performances might be mainly ascribed to the creation of the heterojunction at n-type WO3 and p-type NiO interface, which caused the improvement of the potential barrier and depletion layer. In addition, the larger specific surface area of flower-like nanostructures also possessed abundant sites for surface reaction.

One-step fabrication of 1D p-NiO nanowire/n-Si heterojunction: Development of self-powered ultraviolet photodetector

Even though there are reports on NiO-p/Si-n based photodetector, work along 1D NiO/Si self-powered photodetector remains unexplored. 1D materials offer better electron mobility and can provide ballistic transport channel, which helps in achieving high responsivity. In this work, direct single-step deposition of p-type NiO nanowires on n-type Si as a self-powered photodetector was successfully fabricated by engaging simple electrospinning technique. The structural properties as observed from XRD indicate highly crystalline NiO nanowires and FESEM images revealed 60-75 nm diameter with uniform distribution. Growth of nanowires by using stimuli polymer and its completely removal at high temperature was confirmed using TGA and XPS analysis. The responsivity of the fabricated photodetector was calculated to be 9.1 mA W−1 at zero bias, which can be attributed to the p-type NiO interface with the n-type Silicon, which creates an internal electrical field thereby assisting in the effective separation of the photogenerated carriers. Further, under illumination, at zero bias, the photogenerated current still exists suggesting a generation of internal voltage, which makes the fabricated device as self-powered. This fabrication method will enhance the photodetection properties, and it can be implemented in the fields of optoelectronic devices, sensors, and flexible electronics.

Tailoring the electronic structure by constructing the heterointerface of RuO2–NiO for overall water splitting with ultralow overpotential and extra-long lifetime

RuO2–NiO/NF, obtained through a dip-heating method, achieved continuous electrolysis for 2000 h at an ultrahigh current density. The RuO2–NiO interface promoted H2O dissociation and modulated chemisorbed O-containing intermediates, improving HER and OER activity.

Enhanced photocatalytic activity of ZnO–NiO nanocomposites synthesized through a facile sonochemical route

Formation of heterostructures with p-type oxides such as NiO and CuO is one of the effective methods for improving the photocatalytic performance of ZnO. Such systems are often synthesized through template-based growth techniques that involve many steps. We have prepared ZnO–NiO composites through a facile, template-free, low-temperature sonochemical route. High-resolution transmission electron microscopy analysis indicates the formation of ZnO–NiO heterostructures. Photocatalytic activity of ZnO–NiO nanocomposites in the decomposition of methylene blue dye under solar irradiation is found to be much larger than that of both pure ZnO (1.26 × 10−2 min−1) and NiO (0.31 × 10−2 min−1) establishing synergistic effects. The rate constant increases with increase in the percentage of NiO in the composite and is 6.00 × 10−2 min−1 for sample with the highest percentage of NiO. Rate constants for the second and third runs are estimated to be 4.4 × 10−2 and 4.2 × 10−2 min−1 which are promising. The main mechanism of enhancement of photocatalytic activity of the composites is identified as the more effective separation of the photogenerated free charge carries due to the internal electric field at the ZnO–NiO interface. Sharp decrease in the relative intensity of the band–band emission of ZnO at ~ 380 nm in the case of composite samples and analysis of the relative position of the conduction band and valence band edges of ZnO and NiO support the proposed mechanism.