Ni Surface Research Articles

Eggshell membrane-derived electrocatalysts for water electrolysis

Green H2 (GH2) holds significant promise as a renewable energy resource, particularly in addressing the escalating energy demands sustainably. The imperative for economically viable GH2 technologies, primarily via water electrolysis, has spurred extensive research into suitable electrocatalytic materials. Eggshell membrane (ESM) is typically considered a biowaste material obtained from eggs, which are among the most widely consumed foods both domestically and industrially. Many countries legally require the effective treatment of ESM before disposal to prevent environmental contamination. Therefore, we propose upcycling ESM as an electrocatalytic support, forming transition metal-based active sites through chemical and thermal treatment, followed by doping highly reactive Fe sites electrochemically. ESM’s nanofibrous morphology and porous structure confer catalytic advantages. X-ray photoelectron spectroscopy analysis reveals that certain chemical functional groups in the ESM are involved in the spontaneous electrochemical charge transfer and the adsorption of metal ions, contributing to the formation of metal nanoparticles. Furthermore, various anionic chemical elements such as P, O, N, and S, which originate from intrinsic ESM, can participate in electrocatalysis. The Fe sites electrochemically induced on the Ni and Co nanoparticle surfaces in the ESMs demonstrate excellent electrocatalytic activity and durability toward the oxygen and hydrogen evolution reactions, respectively. This study provides a strategy to utilize ESM as an electrocatalytic material for the development of commercially viable electrocatalysts to produce GH2 by transforming biowaste into value-added materials. Moreover, it promotes the investigation of the (electro)chemical functionalities of biomaterials and the correlation between their functions and electrocatalytic activities.

The importance of long range Fe–Fe interactions in magnetically ordered 2D Fe0.2Ni0.8/Ni(001) and Fe0.3Ni0.7/Ni(001) alloy systems

We develop a theoretical approach to study the magnonic properties of the 2D ordered surface Fe–Ni alloys with 20% and 30% Fe on a face-centered cubic Ni(001) surface substrate. The surface alloy nanostructures in stable equilibrium are determined by computing the lowest energy configurations of constitutive supercells of the ordered alloys. The magnetic exchange constants of the ground state of the stable systems are calculated to define their Heisenberg Hamiltonians using the DFT Spin-Polarized Relativistic Korringa–Kohn–Rostoker (SPRKKR) method and considering Fe–Fe interactions up to third nearest neighbors. To determine the propagating exchange spin-wave modes, evanescent modes, and the consequent magnonic properties, the spin dynamics of the magnetic surface alloy nanostructures are solved using the phase field matching theory (PFMT). Our results indicate that the Fe–Fe exchange interactions up to third nearest neighbors are vital for accurately describing their magnonics. In particular, the exchange interactions influence the form of dispersion branches for the high-energy spin-wave modes of the Fe–Ni surface alloys considered. Appropriate Green’s functions are also derived from the PFMT method to compute the local densities of states (LDOS) for the atomic sites at the surface boundary. For the case of 20% Fe surface alloy, the Fe–Fe exchange interactions shift the Fe LDOS peaks to lower frequency intervals. We also distinguish the emergence of remarkable LDOS peaks for the he case of the 30% Fe surface alloy at specific Ni sites. These peaks change positions under second and third nearest neighbor Fe–Fe interactions, heralding new accessible spin-wave channels. Our results contribute to establishing a systematic understanding of the magnonics of the magnetic surface alloys of transition metal (TM) materials. This new knowledge will enable the study of the quantum transport of spin waves at interfacial alloy nanojunctions composed of such materials. The present DFT-PFMT theoretical approach is general and can be applied to other surface TM alloy magnetic nanostructures.

Theoretical insight into the sulfurated poisoning process of rhenium-doped nickel catalyst

Three rhenium-doped nickel catalyst surfaces including Re-Ni(111), Re-Ni(200) and Re-Ni(220) were built via Re atom substituting one atom of upper layer Ni surfaces. The sulfurated poisoning process involving H2S adsorption and subsequent splitting steps (H2S→HS+H, HS→S+H) on the three surfaces was investigated and further compared using density functional theory (DFT) to understand the crystal-plane effect. For H2S adsorption, the H2S molecule is preferentially adsorbed on the Re top and bridge ReNi1 sites. Re-Ni(200) surface possessed lower H2S adsorption energy compared to Re-Ni(111) and Re-Ni(220) surfaces, due to its smaller coordination number and higher d-orbital intensity at Fermi level. For splitting steps, transition state search showed that the two processes on the three surfaces are all calculated as exothermic while the energy barrier is basically in the range of 0.23 eV∼0.44 eV, which signifies that the poisoning process is favorable both kinetically and thermodynamically. The splitting steps can be described as a dynamic procedure that contains intimate HS fragment activation, S–H bond stretching accompanied by H atom departure and final dissociation into HS+H or S+H co-intermediates. The valence bond changes during dissociation deduced from projected density of states (PDOS) analysis also proved the above procedure.

Comparative Studies on Full Dehydrogenation of Dodecahydro-N-Ethylcarbazole on Pd(111) and Ni(111) Surfaces: Mechanism and Catalytic Enhancement.

Dodecahydro-N-ethylcarbazole (12H-NEC) is regarded as the most promising liquid organic hydrogen carrier for hydrogen storage and transportation. Understanding the mechanism of 12H-NEC dehydrogenation and developing cost-effective catalysts are significant. Pd is a high-performance catalyst for 12H-NEC but is not cost-effective, and Ni is just the opposite. How to understand the whole process of full dehydrogenation and improve the performance of Ni become two key questions. Herein, we systematically investigated the mechanism of the full dehydrogenation of 12H-NEC on Pd(111) and Ni(111) for the first time. By calculating all the barriers in the whole dehydrogenation process, we identified that 3H-NEC to 2H-NEC is the rate-determining step and Ni is catalytically less effective than Pd, which is attributed to its narrower d-band distribution and a 0.32 eV higher d-band center than that of Pd. To improve the performance of Ni, we further introduced dopants of Au, Ag, Cu, Pd, Pt, Ru, Rh, Zn, and Al. We found that Ag doping brings a downshift of the d-band center from -1.29 to -1.67 eV and reduces the barrier of 4H-NEC to NEC from 0.94 to 0.76 eV. This study provides new insights into the catalytic mechanism and performance-tuning strategy to help future experimental synthesis.

Enhanced Hydrodeoxygenation performance through novel Al-Doped radial channel Silica-Supported Carbon-Encapsulated nickel catalysts

Hydrodeoxygenation (HDO) plays a crucial role in upgrading pyrolysis-oil derived from biomass. Here we describe a method for fabricating a carbon-encapsulated nickel metal–acid bifunctional catalyst (Ni@C/RCS-Al) supported on aluminum-doped radial channel silica (RCS-Al). This catalyst exhibits a large surface area and highly dispersed accessible active sites, achieved through a combination of salicylate- and MOF-assisted strategies. The RCS-Al was prepared by a one-pot salicylate-assisted hydrothermal method in an aqueous phase containing an Al source, which is simple, has a high yield, and saves time. The results show that Ni@C/RCS-Al displays a well-defined radial channel pore structure with a mesopore diameter of 31.1 nm, which can significantly increase the number of accessible active sites and accelerate mass transfer. The MOF-assisted strategy leads to the formation of highly dispersed smaller carbon-encapsulated nickel nanoparticle active sites, and Al doping contributes to the adjustable acid sites, demonstrating that Ni@C/RCS-Al is a metal–acid bifunctional catalyst. Importantly, the kinetics study revealed a high reaction constant for the constructed Ni@C/RCS-Al catalyst. Ni@C/RCS-Al demonstrates remarkable performance in HDO, achieving complete m-cresol conversion and 100 % selectivity to the target product methylcyclohexane within a brief period of 75 min (T = 250 °C p = 2 MPa, m-cresol/catalyst (g) = 7.5). This exceptional performance stems from its radial channel pore structure and optimization of metal–acid sites. The thin carbon layer on the Ni surface contributes to its superior stability and water resistance, as verified by an experimental study and DFT calculations. This work opens up a new idea for the application of radial channel silica-supported catalysts in various reactions.

Calculation of Surface Binding Energy in NixPdy Alloys Using Density Functional Theory

In the study, surface binding energies for pure Ni and Pd metals were calculated using density functional theory. The values obtained were 5.32 eV and 4.65 eV, respectively, which represents good accuracy for ab initio calculations. The work also included calculations of surface binding energy for different configurations of NiPd alloys with nickel and palladium concentrations of 66%, 50%, and 33%. Calculations were performed for each type of lattice for both Ni and Pd surface binding energies. Several types of lattices were simulated, and it was found that the average surface binding energies for Ni and Pd are: 5.02 eV and 4.36 eV respectively in the alloy with a Ni concentration of 50%; 4.89 eV and 4.22 eV respectively in the alloy with a Ni concentration of 66%; 5.12 eV and 4.40 eV respectively in the alloy with a Ni concentration of 33%.

Regulate the adsorption of oxygen-containing intermediates to promote the reduction of CO2 to CH4 on Ni-based catalysts

The introduction of oxophilic metals can enhance the selectivity of CO2 reduction reactions (CO2RR) by modulating the adsorption of oxygen-associated active substances on the catalyst surface. Alloying lanthanide atoms into metals has been shown to improve CH4 selectivity by breaking the linear relationship between the adsorption energies of CO* and HxCO*. In this work, a series of oxophilic transition metals (Fe, Mo, Co, Mn) are introduced to explore the influence on the CO2RR. DFT results demonstrate that the doping of oxophilic metals regulates the adsorption strength between the catalyst surface and intermediates, thereby affecting the CH4 and H3COH pathways. Notably, COOH* formation is enhanced on Ni surfaces, leading to increased H3COH production. Ni-Fe and Ni-Mo exhibit significant H3CO* and CO2* binding energies, which reduces the barrier for H3CO*. Meanwhile, the bond energy of M−O is higher than that of C-O in H3CO*, promoting the generation of CH4. The addition of Co and Mn makes the desorbed of HCOOH smaller than the hydrogenation energy barrier, which accelerates the synthesis of formic acid. This research provides a new pathway for the development of inexpensive and resource-rich catalysts.

Water–Gas Shift Activity over Ni/Al2O3 Composites

The water–gas shift (WGS) performance of 10%Ni/Al2O3, 20%Ni/Al2O3 and 10%Ni/CaO-Al2O3 catalysts was studied to reduce CO concentration and produce extra hydrogen. Ni was added onto the Al2O3 support by an impregnation method. The physicochemical properties of nickel catalysts that influence their catalytic activity were examined. The most influential factors in increasing the CO conversion for the water–gas shift reaction are Ni dispersion and surface acidity. Ni metal sites were identified as the active sites for CO adsorption. The main effect of nickel metal was reducing the adsorbed CO amount by reducing the active site concentration. The 10%Ni/Al2O3 catalyst was more active for the WGS reaction than other catalysts. This catalyst presents a high CO conversion rate (75% CO conversion at 800 °C), which is due to its high Ni dispersion at the surface (6.74%) and surface acidity, thereby favoring CO adsorption. A high Ni dispersion for more surface-active sites is exposed to a CO reactant. In addition, favored CO adsorption is related to the acidity on the catalyst surface because CO reactant in the WGS reaction is a weak base. The total acidity can be evaluated by integrating the NH3-Temperature-Programmed Desorption curves. Therefore, an enhancement of surface acidity is identified as the favored CO adsorption.

Ni coarsening under humid atmosphere in the electrode of solid oxide cells: A combined study of density-functional theory and phase-field modeling

Ni coarsening in solid oxide cell (SOC) electrodes is known to be significantly faster under a humid atmosphere. The underlying mechanisms, though, have not been fully understood. In this work, we examine the surface diffusion of Ni(OH)x by a combination of density-functional theory and phase-field modeling. Density-functional theory is used to evaluate the adsorption and diffusion of the Ni(OH)x species on Ni (111) surface, and the results are used to obtain the effective surface diffusivity of Ni versus steam and hydrogen gas partial pressures. This diffusivity is used as an input for a phase-field model to investigate the Ni coarsening in SOC electrodes. It is found that Ni(OH)x formed through chemical reaction cannot accelerate coarsening unless an extremely high steam to hydrogen ratio is reached. However, if Ni(OH)x is formed through electrochemical reactions near triple phase boundaries (TPBs), surface diffusion of Ni(OH)x may cause faster Ni coarsening in fuel cell mode under a large overpotential. Specifically, surface diffusion of Ni(OH) may be comparable to or faster than that of Ni under an overpotential that is large but still possible under fuel cell operating conditions.

Adsorption Properties of Au−Ni Surface Alloys with a Nonstoichiometric Moiré Structure: A Density Functional Theory Study

Adsorption Properties of Au−Ni Surface Alloys with a Nonstoichiometric Moiré Structure: A Density Functional Theory Study

Density functional theory analysis of the stability of H[formula omitted]O and CO[formula omitted]-derived surface species over low-index Ni facets

Analysis of stability of chemical species over catalytic surfaces is crucial for understanding the surface-specific effects to reach optimal catalyst composition. With reference to CO2 hydration, we undertook the task of unravelling the same over Ni surfaces, and examined the effect of exposed surface facets on the stability of relevant surface species. By examining H2O and CO2-derived surface species over Ni(100), Ni(110), and Ni(111) surface facets, we investigated the adsorption and dissociation of H2O and CO2-derived surface, enabling a thorough comparison of facet effects. A linear scaling relationship between the adsorption energy of the adsorbates and Bader charges was observed, providing an evidence that the binding energy of surface species originating from H2O and CO2 was closely correlated to the degree of electron transfer from Ni to the adsorbed species. Understanding of the binding and stability of H2O and CO2-derived species over Ni surfaces was furthered by the analysis of the charge density iso-surfaces. Stability plots and reaction paths highlighted Ni(100) and Ni(110) to be superior to Ni(111). Ni(110) exhibited the lowest H2O dissociation barrier, while Ni(100) showed favourable CO2 dissociation barriers citing Ni(110) surface facet as the most suited plane for selective CO2 hydration.

Bacterial adhesion and corrosion behavior of different pure metals induced by sulfate reducing bacteria

The corrosion behaviors of four pure metals (Fe, Ni, Mo and Cr) in the presence of sulfate reducing bacteria (SRB) were investigated in enriched artificial seawater (EASW) after 14-day incubation. Metal Fe and metal Ni experienced weight losses of 1.96 mg cm−2 and 1.26 mg cm−2, respectively. In contrast, metal Mo and metal Cr exhibited minimal weight losses, with values of only 0.05 mg cm−2 and 0.03 mg cm−2, respectively. In comparison to Mo (2.2 × 106 cells cm−2) or Cr (1.4 × 106 cells cm−2) surface, the sessile cell counts on Fe (4.0 × 107 cells cm−2) or Ni (3.1 × 107 cells cm−2) surface was higher.

Deciphering the stability mechanism of Pt-Ni/Al2O3 catalysts in syngas production via DRM

Deactivation induced by coke deposition remains the foremost challenge in using Ni-based catalysts for the production of syngas via dry reforming of methane (DRM) reaction. Herein, highly dispersed Pt-Ni/Al2O3 bimetallic catalysts prepared by atomic layer deposition (ALD) displayed remarkable stability at 650 ℃ in the DRM reaction. The Pt-Ni catalysts underwent an activation process within the initial 10 h and maintained its activity without deactivation throughout the subsequent aging testing up to 48 h. In contrast, the Ni/Al2O3 rapidly deactivated over time. Despite its high CH4 conversion rates, the Pt-Ni bimetallic catalyst produced a substantial quantity of carbon nanotubes (CNTs) analogous to the Ni/Al2O3 catalyst. The discrepancy in stability performance between two catalysts derived from disparities in the carbon sites and structural defects evolving over reaction time. Regarding the catalysts with Pt decoration on the Ni surface, CNTs exhibited increasing structural defects and gradually deposited on the Al2O3 support without fully encapsulating the metal active sites, as evidenced by CH4-TPD experiments. In the case of Ni nanoparticles on Al2O3, crystalline CNTs with fewer defects accumulated, leading to rapid deactivation. These findings enhance our understanding of coke resistance in DRM catalysts and help the development of more robust bimetallic catalyst systems.

CO2 reforming of ethane using Ni-La intermetallic sites within a nanocapsule framework

CO2 reforming of light alkanes from unconventional gas resources (shale gas/coalbed gas) presents an attractive route to achieve CO2 utilization and valuable chemical production. However, it remains challenging in both high stability and product selectivity due to the inevitable strong competition between dry reforming and oxidative dehydrogenation pathways. We report here a La modified Ni@SiO2 nanocapsule as the thermal-catalyst for CO2 reforming of ethane, achieving complete ethane conversion and remarkable CO2 conversion of 86.5 %, with stability for more than 200 h experiencing no carbon deposition. Detailed kinetic study, in situ characterizations and DFT calculation results revealed that the formation of NiLa intermetallic sites improved the adsorption of active oxygen species and activation of C2H6, which stabilized the key intermediate CH3CH2O* as well as the subsequent C2* cracking to CHx(O)*, leading to high selectivity toward syngas. Meanwhile, the removal of carbon deposits on Ni-La2O3 interfaces are faster than Ni surface. The synergism of spatial confinement structure provided by the nanocapsule with sufficient mechanical strength together with the chemical Ni-La2O3 interface of the enwrapped Ni-La mixed metal (oxide) NPs can timely eliminate C2* intermediates, which results in the most effective anti-coking ability during ethane reforming. This work highlights a tangible process towards unconventional (C2+) gas utilization with fine-tunable nanoreactor catalysts.

Bond-selective effect for the dissociative chemisorption of HOD on the Ni(100) surface revealed at the full-dimensional quantum dynamical level.

We present a comprehensive investigation into the dissociative chemisorption of HOD on a rigid Ni(100) surface using an approximate full-dimensional (9D) quantum dynamics approach, which was based on the time-dependent wave-packet calculations on a full-dimensional potential energy surface obtained through neural network fitting to density functional theory energy points. The approximate-9D probabilities were computed by averaging the seven-dimensional (7D) site-specific dissociation probabilities across six impact sites with appropriate relative weights. Our results uncover a distinctive bond-selective effect, demonstrating that the vibrational excitation of a specific bond substantially enhances the cleavage of that excited bond. The product branching ratios are substantially influenced by which bond undergoes excitation, exhibiting a clear preference for the product formed through the cleavage of the excited bond over the alternative product.

New evidence on the electroprecipitation of ceria

The electroprecipitation of ceria onto Ni electrodes from Ce(NO3)3 solutions has been studied by comparing deposits obtained with potentiostatic electrolysis of variable durations. The dependence on the deposition charge of (i) ceria layer thickness, (ii) apparent layer density, (iii) coverage of the Ni surface by CeO2 and (iv) layer resistance was determined. These quantities were respectively assessed using (i) cross-sectional SEM images, (ii) gravimetric measurements, (iii) cyclic voltammetry in alkaline solution and (iv) electrochemical impedance spectroscopy. Experimental data showed that a porous low-density oxide precipitated initially, leaving a substantial part of the Ni electrode surface in direct contact with the electrolyte. During successive phases of the film growth, the formation of new solid material at the layer|solution interface was progressively replaced by its formation within the layers’ pores and at the Ni|layer interface.

A Blyholder mechanism in the chemisorption of N2O on Ni(111) – studied with Auger-photoelectron coincidence spectroscopy

In heterogeneous catalysis the surface-adsorbate bond strength is critical for the function of the system. Here we study a series consisting of multilayer, bilayer and monolayer N2O on Ni(111) and employ Auger-photoelectron coincidence spectroscopy (APECS) to study the interaction between the molecule and the substrate directly. We observe intensity in the nitrogen Auger spectra that arise from the interaction between molecule and surface (not observed in free molecules) whereas the oxygen spectra are thickness-independent. Since the two nitrogen atoms of N2O are chemically inequivalent we can assign the intensity present in the bilayer and monolayer cases to orbitals centered on the terminal nitrogen which is closest to the Ni(111) surface. Using ab initio, molecular dynamics and solid-state density functional theory calculations we infer a Blyholder model of the surface bond as consisting of donation from the terminal nitrogen lone-pair valence orbital with back-donation from the metal into the unoccupied orbitals on that nitrogen. This coincidence technique can readily be used to study substrate–adsorbate interactions directly with chemical and orbital specificity — this opens up prospects to study fundamental steps of molecular adsorption and heterogeneous catalysis with unprecedented detail.

Highly efficient selective hydrogenation of adiponitrile to hexamethylene diamine over barium and melamine formaldehyde resin-modified nickel–cobalt-based zeolitic imidazolate framework-derived catalyst

In the present study, the catalyst modified with alkaline oxide can enhance the selectivity to primary amines. However, the addition of alkaline oxide inevitably reduces catalytic activity. In this study, NiCo-NC@BaO-MFC catalyst derived from zeolitic imidazolate framework-67, Ba(CH3COO)2, and melamine formaldehyde (MF) resin was prepared and used for the hydrogenation of adiponitrile (ADN) to hexamethylene diamine (HDMA). The carbon layer obtained from the MF resin effectively prevents the interaction between barium (Ba) and the active center, thus improving target product selectivity without decreasing catalytic activity. The results of the density functional theory (DFT) calculation and characterization indicated that the effect of synergy between nickel (Ni) and cobalt (Co) bimetals induces an electron density growth on the Ni surface, bringing the d-band center toward the Fermi surface. Meanwhile, the high electron density of the active center compensates for the electron-deficient state of the carbon atom in –CN, thus improving the catalytic activity. Furthermore, it was found that the introduction of Ba promotes the formation of nucleophilic hydrogen anions, which facilitates the hydrogenation of 6-aminohexylimine (AHIM) to HDMA and inhibits the intramolecular condensation of AHIM, hence improving the selectivity to HDMA. The NiCo-NC@BaO-MFC catalyst gives 98.6 % ADN conversion and 97.2 % selectivity to HDMA in an alkali-free system.

Two birds with one stone: A “needle-like” structure constructed on multifunctional PET fabric surface for flame retardancy and electromagnetic interference shielding

Here, a facile method is reported to prepare multifunctional PET fabrics with high flame retardancy, hydrophobicity and ideal electromagnetic shielding. PET fabric was firstly modified via polydopamine with mussel-like structure, and then DOPO@ZnO was constructed. A new type of composite PET fabric was prepared by simple, low-cost electroless Ni process and surface PDMS treatment (PpDPNP). The resulting composite fabric was extensively investigated for its stability and applicability in a complicated environment. The conductive interconnection network of modified fabric made it have excellent electrical conductivity and mechanical properties. Even after solution corrosion and washing, the prepared composite fabric could maintain a relatively stable electrical conductivity. The conductivity, tensile and elongation at break of composite fabric were 144.62 S/cm, 78.48 MPa and 167.49 %, respectively. The average electromagnetic interference shielding effectiveness (EMI SE) of PpDPNP reached 58.83 dB with 0.18 mm thickness and electroless Ni only 20 min at X-band, which was mainly due to large dielectric loss and multiple reflections. The modified PET fabric had self-extinguishing performance, and peak heat release rate (PHRR) and total heat release rate (THR) were 60.7 % and 59.8 % lower than pure PET fabric, respectively, indicating that the composite fabric had excellent flame retardancy.

Ring–Opening Mechanism of O‐heterocycles into α,ω‐Diols over Ni−La(OH)3: C−O Bond Hydrogenolysis of THFA to 1,5‐Pentanediol as a Case Study

AbstractThe elucidation of the ring–opening reaction mechanism is a critical step towards improving the catalytic performance for the conversion of biomass into value–added chemicals. Herein, we focused on the stepwise C−O bond hydrogenolysis mechanism of oxygen–containing heterocycles (O‐heterocycles) into α,ω‐diols, in particular THFA to 1,5‐PeD, over selective Ni−La(OH)3 in hydrogen–donor isopropanol. A mechanistic study was carried out on a structurally well–defined Ni−La(OH)3, where the mechanism was elucidated using a combination of kinetic and 13C NMR isotope labeling experiments. It was suggested that both Ni nanoparticles and La(OH)3 support play a critical role in the reaction mechanism, where basic hydroxide species of the support initially deprotonate the CH2OH and −OH modified furan, tetrahydrofuran and tetrahydropyran rings, adsorbing them chemically on the catalyst surface. This step is followed by a direct hydride attack on the second carbon atom of these rings, which is proposed to be the key step for ring cleavage, as indicated by the increased deuteration at this position. In addition to the direct hydrogenolysis using gaseous H2, it is assumed that a catalytic transfer hydrogenolysis reaction (CTH) reaction of THFA is proposed to proceed via the dehydrogenation of isopropanol over isolated Ni species, forming hydrogen species that can be adsorbed on the Ni surface or desorb as H2 molecules.