Ni-Co Bimetallic Catalyst Research Articles

Fabrication of lignin-MOF derived spherical carbon supported NiCo-bimetallic catalysts for selective hydrogenolysis lignin derived ether.

The conversion of abundant lignin was of great significance for the utilization of biomass resources. In this study, lignin sulfonate (LS) was selected as a carbon-based support, which was successfully introduced into the NiCo-MOF structure. A series of lignin and MOF hybrid catalysts (NinCo-MOF-LS) with varying metal ratios of Ni and Co were synthesized via the hydrothermal method. Subsequently, the catalytic hydrogenolysis of lignin-derived dimers was conducted over a range of NinCo-MOF-LS, with the impact of calcination temperature and lignin addition in the catalysts taken into account. The selective conversion of benzyl phenyl ether (BPE) and other lignin dimers was achieved over the NinCo-MOF-LS catalyst with isopropanol serving as the hydrogen donor solvent in a nitrogen atmosphere. The Ni/Co metal ratio and calcination temperature were found to have a significant impact on the catalytic performance. Through a comprehensive investigation of various reaction parameters, including temperature, pressure, reaction time, and reaction solvent, it was determined that the catalyst exhibited excellent catalytic activity in the selective hydrogenolysis of BPE to cycloalkane and cyclohexanol. The optimal reaction conditions (240°C, 4h, 3MPaN2) were found to be conducive to the effective conversion of BPE into methylcyclohexane and cyclohexanol. The combination of lignin and metal-organic framework represented a novel approach to the utilization of lignin resources and the upgrading of biomass-derived chemicals.

Ni-Co Bimetallic Catalysts Supported on Mixed Oxides (Sc-Ce-Zr) for Enhanced Methane Dry Reforming.

Dry methane reforming (DRM) presents a viable pathway for converting greenhouse gases into useful syngas. Nevertheless, the procedure requires robust and reasonably priced catalysts. This study explored using cost-effective cobalt and nickel combined into a single catalyst with different metal ratios. The reaction was conducted in a fixed reactor at 700 °C. The findings indicate that the incorporation of cobalt significantly enhances catalyst performance by preventing metal sintering, improving metal dispersion, and promoting beneficial metal-support interactions. The best-performing catalyst (3.75Ni+1.25Co-ScCeZr) achieved a good conversion rate of CH4 and CO2 at 46.8 %, and 60 % respectively after 330 minutes while maintaining good stability. The TGA and CO2-TPD analysis results show that the addition of Co to Ni reduces carbon formation, and increases the amount of strong basic sites and isolated O2- species, and the total amount of CO2 desorbed. These results collectively highlight the potential of cobalt-nickel catalysts for practical DRM applications and contribute to developing sustainable energy technologies.

Formate and CO* Radicals Intermediated Atmospheric CO2 Conversion over Co-Ni Bimetallic Catalysts Assembled on Diatomite.

There exists an imperative exigency to ascertain catalysts of cost-effectiveness and energy efficiency for the facilitation of industrial CO2 methanation. In this area, the dual metal synergistic enhancement of the metal-support interaction emerges as a highly promising strategy. Here, Diatomite (Dt) was used as the support, and a series of CoyNi/Dt (Co as the first component and Ni as the second component) composite catalysts were constructed using an ultrasound-assisted coimpregnation method. Different Co/Ni molar ratios had a significant impact on the phase structure, chemical properties, morphological characteristics, and NiCo crystal structure of the xCoyNi/Dt materials. When the Co/Ni molar ratio was set to 2.0, a Ni-Co alloy was obtained, which is the key to improve the catalytic activity. Compared to the other xCoyNi/Dt catalysts, the bimetallic catalyst 2Co1Ni/Dt exhibited superior CO2 catalytic performance and stability, achieving a 76% CO2 conversion and 98% CH4 selectivity at 425 °C. The in situ DRIFTS results indicated that CO2 methanation over the 2Co1Ni/Dt catalyst followed the reaction pathway with formate and CO* radicals as the intermediates.

Highly efficient selective hydrogenation of furfural to tetrahydrofurfuryl alcohol over MOF-derived Co-Ni bimetallic catalysts: The effects of Co-Ni alloy and adsorption configuration

The targeted conversion of furfural (FA) over inexpensive catalyst is a critical and challenging project. Herein, CoNi alloy catalysts (xCoyNi/C) were prepared through one-step pyrolysis of metal–organic frameworks and used in furfural (FA) hydrogenation to tetrahydrofurfuryl alcohol (TFOL). The formation of CoNi alloy leads to a reconfiguration of the electronic structure on the metal surface, which affects the adsorption of functional groups on FA and furfuryl alcohol (FOL). In situ FT-IR analysis and DFT calculations verify that bimetallic CoNi alloy catalyst exhibits more suitable reactants adsorption and hydrogenation rate in comparison with the monometallic Co and monometallic Ni catalysts. Meanwhile, CoNi alloy significantly reduces the activation barrier from FOL to TFOL. Hence, the 1Co1Ni/C catalyst gives the highest TFOL yield of > 99 %. This study provides a simple strategy for the preparation of alloy catalysts for tuning product selectivity and presents practical potential for upgrading biomass-derived platform molecules.

Comparison between the structural characteristics and process activity of bulk and mesoporous Ni-Co-Ce/Al2O3 catalysts in the dry reforming of methane

Dry reforming of methane (DRM) is a potential way to exploit greenhouse gases and generate hydrogen. Catalyst deactivation is the biggest DRM commercialization obstacle. Lately, Ni-Co bimetallic catalysts have demonstrated improved carbon resistance over Ni-based catalysts. The aim of this research is not just to investigate the impact of Ni-Co catalysts on the DRM activity, but also to evaluate the Ni-Co alloy creation effect on the catalyst characteristics and activity. Mesoporous alumina (MA) was used as a catalyst support for Ni-Co particles in this process and its structure and activity were compared to those of bulk alumina (BA) supported catalysts. In addition, cerium was included into all of the catalysts developed as a suitable promoter for reducing the amount of deposited coke. The results obtained from the XRD and nitrogen adsorption/desorption analysis indicated the formation of a mesoporous structure and nanocrystalline morphology in the Ni-Co/MA samples, as compared to the Ni-Co/BA ones. The results showed that the bimetallic 2Ni-1Co-1Ce/MA sample had the best catalytic activity, with a CH4 conversion of 98.30 %, CO2 conversion of 96.35 %, and H2 yield of 96.30 % at 700 °C.

Response optimisation of TiO2-supported bimetallic NiCo catalyst for the cracking and deoxygenation of waste cooking oil into jet-fuel range hydrocarbon fuels under non-hydrogen environment

Waste cooking oil is a sustainable feedstock that can be utilised to produce biojet fuel via the hydrodeoxygenation process. However, the need for hydrogen for the hydrodeoxygenation process incurs high cost. In the present work, a type of bimetallic catalyst that can deoxygenate and selectively crack free fatty acids under hydrogen-free conditions was developed. The NiCo/TiO2 catalyst was prepared via the impregnation of varying amounts of Ni and Co salts onto TiO2. Optimisation of the production conditions was performed via response surface methodology based on the Box-Behnken experimental design to maximise the deoxygenation and biojet fuel yield. A maximum deoxygenation yield of 83.13 % with 44.5 % biojet fuel selectivity was obtained from the experiment and optimisation based on Box-Behnken design (R2 > 0.9). Incorporation of Ni and Co onto TiO2 reduced the surface area of the catalyst, but active metal dispersion significantly improved the deoxygenation performance and biojet fuel selectivity. The viscosity, flash point, freezing point and net heat of combustion value of the liquid product were within the jet fuel standard specifications. Overall, the study shows the potential of bimetallic NiCo/TiO2 catalyst in waste cooking oil deoxygenation for biojet fuel production.

Unraveling the mechanistic interplay between CO and CO2 hydrogenation over Ni, Co, and NiCo catalysts

Although CO and CO2 hydrogenation reactions have been extensively studied, there is still significant controversy regarding the mechanism of methane formation and the routes for byproducts, especially when both carbon sources are simultaneously present. This work combines kinetic, operando-spectroscopic, isotopic techniques and DFT calculations to elucidate the relationships between CO and CO2 hydrogenation over mono Ni, Co and bimetallic NiCo catalysts with similar metal dispersion. The bimetallic catalysts showed a slight synergistic effect for methane formation from CO, while from CO2 the effect was opposite, showing a negative shift of activity as compared with those observed on the monometallic catalysts. The kinetic analysis shows similar apparent order with respect to H2 (∼0.5) and an inverse secondary isotope kinetic effect (<1) for both methanation reactions, suggesting that CH4 formation proceeds via C-O bond breaking in an H*-assisted mechanism, where the rate-determining step was not shown to be sensitive to the carbon source. The anti-synergistic effect observed on the bimetallic catalysts during CO2 hydrogenation is explained by the formation of unreactive HCOO* species (spectator), which generate a lower density of methane intermediates. On the other hand, the formation of the undesired products, i.e., CO or CO2 during CO2 or CO hydrogenation, respectively, shows relevant differences since the CO formation during CO2 hydrogenation proceeds through the desorption of the carbonyl species adsorbed on weak sites, meanwhile the CO2 formation from CO hydrogenation is due to a minority route of direct dissociation of CO, allowing the rejection of O* with CO* to produce CO2. This study contributes to elucidate the routes that determine the selectivity and reactivity for CO and CO2 hydrogenation and their mechanistic relationship. This information is valuable for the rational design and development of new materials with high performance during hydrogenation processes.

Chemocatalytic Oxidation of 5‐hydroxymethylfurfural into 2,5‐furandicarboxylic Acid Over Nickel Cobalt Oxide

AbstractThe present study reports the synthesis, characterization, and application of NiCo bimetallic catalysts to produce 2,5‐furandicarboxylic acid (FDCA) via the oxidation of bio‐renewable 5‐hydroxymethylfurfural (HMF). FDCA is a biopolymer precursor and a potential replacement for terephthalic acid (TPA). The catalysts were synthesized via the co‐precipitation method in different molar ratios of NiCo, followed by calcination in a muffle furnace. As a result, the complete conversion of HMF and a maximum 84.89 % FDCA yield was measured at 50 °C in 50 minutes in the presence of NiCo(3 : 1) catalyst. In addition, effect reaction parameters, including catalyst amount, temperature, time, base, and oxidant amount on the FDCA yield, were studied, and the process was optimized. The NiCo(3 : 1) catalyst showed a negligible loss in activity for at least five cycles. The higher catalytic activity and stability are attributed to the synergistic effect of bimetallic catalysts, such as higher lattice oxygen. Accordingly, the catalyst was characterized using BET, XRD, H2‐TPR, CO2‐TPD, HR‐TEM, and XPS to correlate their properties and activity. The reaction products were analyzed quantitatively using HPLC and qualitatively using HR‐MS.

Bimetallic Ni-Co catalyst for improving selectivity in transfer hydrogenation of phenolic compounds

The study investigated the transfer hydrogenation of guaiacol, anisole, phenol, and positional isomers of dimethoxybenezene using 2-PrOH as the H-donor over Ni, Co, and Ni-Co catalysts. The catalysts, which contained 5 wt% metal, were prepared by the deposition-precipitation method. The results showed that the catalysts had developed a pore structure and fine metal particles. The Ni and Ni-Co catalysts demonstrated exceptional activity in the transfer hydrogenation of phenolic compounds with a substrate to metal molar ratio of 100 to 1. Furthermore, the addition of Co to Ni significantly impacted the selectivity of transfer hydrogenation promoting hydrodeoxygenation of anisole and guaiacol.

Insight into role of Co species on NiCo/CeMgAl for ethanol steam reforming: Enhanced activity and resistance to coke

Bimetallic catalysts with unique geometric and electronic structure exhibit high performance compared to that of monometallic counterparts in the ethanol steam reforming (ESR). Herein, NiCo bimetals supported on CeO2 doped MgAl2O4 (NiCo/CeMgAl) with different ratio of Ni/Co were prepared for ESR. The synergies between Ni and Co in catalytic activities and ability to anti-coking were focused. The results demonstrate Co atoms trend to segregate toward the surface and are oxidized synchronously, forming the Ni-CoO hybrid surface. The reduced Ni particles are beneficial to maintain a stable catalytic activity for the C-C bonds scission, and the CoO particles formed by segregation and irreversible oxidation of Co0 are more conducive to activation of H2O, the resulting OH promotes the transformation of CHx species, which significantly reduces the selectivity of CH4 and prevents the formation of filamentous carbon. Controlling Co content and maintaining a stable M/Mδ+ are critical to balance the C-C bond scission reaction and the CH3* conversion reaction on the NiCo bimetallic catalysts. The optimal catalyst 9Ni1Co/CeMgAl shows the ethanol conversion of 93.9 % at TOS of 100 h, and the average rate of coke formation is 0.50 mgc·gcat-1·h−1.

Catalytic evaluation of Pd-promoted Ni-Co/Al2O3 catalyst for glycerol dry reforming: Assessing hydrogen-rich syngas production, kinetics and mechanisms

The Pd-promoted Ni-Co bimetallic catalysts were prepared using ultrasonic-assisted impregnation, and their performance was subsequently assessed in a fixed-bed reactor. The catalyst's performance was evaluated in glycerol dry reforming (GDR) over a range of temperatures, from 873 K to 1173 K and reactant partial pressures ranging from 10 kPa to 40 kPa. The results indicated that as the temperature was raised from 873 K to 1073 K, there was a noticeable rise in both reactant conversion and product yield. However, beyond 1173 K, catalytic performance declined due to glycerol thermal cracking and sintering of the support at high temperatures, resulting in increased carbon formation. The presence of excessive CO2 was found to suppress glycerol adsorption on the catalyst surface, causing a decline in catalytic activity with a CO2 partial pressure of more than 20 kPa, regardless of reaction temperature. Additionally, excess CO2 were found to enhance the side reaction, particularly reverse water-gas shift (RWGS) that related to produce intermediate H2O. Similarly, the glycerol partial pressure was found to impact catalytic performance, with a decrease in performance beyond 20 kPa due to competing reactants between glycerol and CO2. According to the Langmuir-Hinshelwood kinetic mechanism, a dual molecular adsorption site for glycerol and CO2 was appropriate for this GDR reaction, with an associated activation energy of 47.3 kJ mol−1. The GDR reaction was identified as a kinetically controlled process due to its high activation energy, more than 25 kJ mol−1. The plausible mechanism of GDR over Pd-Ni-Co/Al2O3 occurred through the dissociative-type of adsorption of on active metallic sites of the catalysts for both reactant (glycerol and CO2). This was further facilitated by the bifunctional mechanisms based on H2 generated from dissociative adsorption involving both catalyst's basic sites and metallic active sites. This was ascribed to the highly dispersed and strong interaction between metal-support in Pd-promoted Ni-Co bimetallic catalysts.

Pd+Al2O3-Supported Ni-Co Bimetallic Catalyst for H2 Production through Dry Reforming of Methane: Effect of Carbon Deposition over Active Sites

Dry reforming of methane (DRM) is gaining global attention due to its capacity to convert two greenhouse gases together. It proceeds through CH4 decomposition over active sites (into CH4−x) followed by CH4−x oxidation by CO2 (into syngas). Furthermore, CH4−x oligomerization into coke cannot be neglected. Herein, xNi(5−x)Co/Pd+Al2O3 (x = 5, 3.75, 2.5, 1.25, 0) catalysts are prepared, investigated for DRM, and characterized with X-ray diffraction, UV-Vis, transmission electron microscopy, temperature-programmed reduction/desorption techniques, and thermogravimetry. Fine-tuning among stable active sites, graphitic carbon deposits, and catalytic activity is noticed. The total reducibility and basicity are found to decrease upon increasing the Co proportion up to 2.5 wt% in the Ni-Co bimetallic Pd+Al2O3-supported catalyst. The active sites derived from strong metal–support interaction species (NiAl2Ox or dispersed CoOx) are found to be promising in higher levels of activity. However, activity is, again, limited by graphitic carbon which is increased with an increasing Co proportion in the Ni-Co bimetallic Pd+Al2O3-supported catalyst. The incorporation of 1.25 wt% Co along with 3.75 wt% Ni over Pd+Al2O3 results in the generation of fewer such active sites, extensive oxidizable carbon deposits, and inferior catalytic activity compared to 5Ni/Pd+Al2O3. The 2.5Ni2.5Co/Pd+Al2O3 catalyst has lower crystallinity, a relatively lower coke deposit (than the 3.75Ni1.25Co/Pd+Al2O3 catalyst), and a higher number of stable active sites. It attains a 54–51% H2 yield in 430 min TOS and 0.87 H2/CO (similar to 5Ni/Pd+Al2O3)

Effect of Ni-Co addition on Pd promoted Al2O3 catalysts for dry reforming of methane

This study investigates the effectiveness of x Ni – (5 – x) Co / 5 Pd – Al2O3 (where x=0, 1.25, 2.5, 3.75, and 5) bimetallic catalysts and the influence of the Pd on their activity in the dry reforming of methane. Comprehensive characterization techniques including XRD, TPR, TPD, SEM, TGA, and Raman analysis are employed to examine the catalysts. XRD analysis of the calcined catalysts reveals the presence of multiple oxides such as NiO, CoO, Co3O4, and PdO. The metal-support interaction and the particle sintering of the catalysts depend on the amount of Co loading, for higher Co loadings (> 2.5 wt%) resulted in weakened metal-support interaction as indicated by TPR analysis. Also, the particle sintering was observed with an increase in Co loading observed from SEM and TEM analysis. The activity analysis demonstrates that the 5 Ni / 5 Pd – Al2O3 catalysts exhibit superior performance in terms of both CH4 (59%) and CO2 (64%) conversions, as well as stability, compared to the Ni-Co bimetallic catalyst. The addition of Co leads to decreased activity, Furthermore, TGA analysis indicates minimal carbon deposition on the 5 Ni / 5 Pd – Al2O3 catalyst during the 7-hour activity study. Notably, Raman analysis reveals a lower presence of graphitic carbon on the catalyst, which contributes to its stable catalytic activity. The presence of Pd in the 5 Ni catalyst reduces carbon deposition and enhances its activity. However, in the case of the Ni-Co bimetallic catalyst, the promotional effect of Pd appears to be negligible. Overall, these findings emphasize the promising potential of the 5 Ni / 5 Pd – Al2O3 catalyst for efficient and stable dry reforming of methane.

Lignite-char-supported highly dispersed ultrasmall Ni-Co alloy for stably dry reforming of methane at low temperature

Lignite, abundant in oxygen-containing functional groups, can disperse metal ions through an ion-exchanging method to prepare highly dispersed metal catalysts. Herein, we prepared the Ni-Co bimetallic catalysts using this method and tested their activity and stability in the dry reforming of methane reaction. The Ni0.05-Co0.1 with Ni/Co mass ratio of 1:10 exhibited superior performance due to its higher specific surface area (386 m2/g), smaller metallic particle size (4.85 nm), better dispersion and moderate basicity (0.023 mmol/g), showing the best activity at 650 °C, 2400 mL.h−1.g−1 and atmospheric pressure, with a conversion of 71.5% for CH4, 82.8% for CO2, and a molar ratio of H2/CO of 0.73. Additionally, the catalyst maintained a stable activity throughout a continuous 30 h test at 650 °C, 7200 mL.h−1.g−1 and 0.3 MPa. Overall, this study demonstrates that lignite-char-supported Ni-Co alloy catalysts show great potential for DRM reaction particularly at relatively low temperature and elevated pressure.

Cobalt Nickel Bimetallic Nanocatalyst Supported on g‐C3N4 for Selective Hydrogenation of α,β‐Unsaturated Carbonyls and Nitroarenes

AbstractDesigned CoNi bimetallic catalysts on various supports were synthesized and tested for selective hydrogenation reactions. Amongst these, the newly developed CoNi@gC3N4 nanocatalyst demonstrated a unique reactivity profile. It was found to be most effective for selective hydrogenation of various chalcone derivatives and nitroarenes in the presence of other reducible functional groups such as halo, carbonyl, benzyl ether, cyclopropane, and isolated alkenes. The prepared bimetallic catalyst has advantages over the reported methods in terms of catalytic activity under mild conditions, selectivity, and reusability. The catalyst CoNi@gC3N4 has ability to selectively reduce nitro functional group to amine and allows formation of quinolines.

Selective hydrodeoxygenation of monophenolics from lignin bio-oil for preparing cyclohexanol and its derivatives over Ni-Co/Al2O3-MgO catalyst

It is of significance to efficiently convert renewable and sustainable lignin bio-oil into cyclohexanol and its derivatives by selective hydrodeoxygenation to alleviate excessive dependence on fossil resources. However, the complicated components of lignin bio-oil hindered its application as bulk chemicals. A bimetallic Ni-Co catalyst supported on MgO-modified γ-Al2O3 was constructed for the catalytic hydrodeoxygenation of monophenolics from lignin bio-oil. The bimetallic catalyst with adding Co increased active centers and acid sites, improving the catalytic activity to the hydrodeoxygenation, compared to the Ni-based catalyst. The proper addition of MgO into the catalyst carrier increased the interplay among the Ni, Co particles and the catalyst carrier owing to the electron transfer from MgO into Ni and Co species. The enhanced interplay between active metal particles and the catalyst carrier benefited the dispersion of Ni, Co particles, and the average Ni and Co particle size decreased from 14 nm to 10 nm. Furthermore, MgO increased the basic sites, which effectively inhibited the elimination of the hydroxyl groups in phenols and preserved hydroxyl groups, resulting in a significant improvement in the selectivity of cyclohexanol and its derivatives. Ni-Co/Al2O3-MgO with good cycling stability contributed to a 65.6 wt% yield of cyclohexanol and its derivatives when the hydrodeoxygenation of monophenolics (such as guaiacol, 2,6-dimethoxyphenol and their alkyl substitutes) was pursued in isopropanol at 300 ℃ and 2 MPa H2 for 5 h. It was found that excessive dosage of the catalyst, higher temperature and hydrogen pressure, as well as longer reaction time, caused the excessive hydrodeoxygenation of monophenolics and hence decreased the selectivity to cyclohexanol and its derivatives. This work might provide a new idea for the high-value utilization of lignin bio-oil.

Bimetallic Ni-Co Alloy Derived from Perovskite as Precursor on SiO2 as Catalysts for CO Methanation

The supported bimetallic Ni-Co alloy catalysts modified with La2O3 were prepared by using the perovskite composite oxide of LaNi[Formula: see text]Co[Formula: see text]O3/SiO2 as the precursor, which were obtained by the impregnation method combined with the citrate complex method. The samples were characterized through using XRD, BET, H2-TPR, CO-TPD, TG and XPS, and the catalytic performances for CO methanation was investigated. The component among the bimetallic (Ni-Co) alloy-La2O3/SiO2 catalyst would be mutually diluted, consequently exhibiting pretty good resistance to metal sintering. The carbon deposition on the catalyst surface mainly depends on the adsorption form of CO, the doping of Co changed the adsorption form and adsorption strength of Co, thereby, the bimetallic Ni-Co catalyst showed strong resistance to carbon deposition. Comparing with the mono-metallic nickel catalyst, the supported bimetallic Ni-Co alloy catalysts exhibited good catalytic activity, selectivity and stability for CO methanation, especially excellent resistance to carbon deposition and metal sintering.

Selective hydrogenation of diphenyl ethers over NiCo bimetallic catalyst

The selective cleavage of ether bonds by non-noble metal catalysts is crucial for the valorization of lignin. Bimetallic catalysts were prepared by wet impregnation using SiO2-Al2O3 as the supports and Ni and Co as the active metal sites. The prepared bimetal catalysts possess higher catalytic activity than single Ni or Co catalysts and could efficiently cleave the CO bonds of diphenyl ether (DPE), under relatively mild conditions (160 °C, 1 MPa H2, 2 h). The XPS characterization suggested the interactions between Ni and Co in the bimetal catalysts, which could bring synergy effects between metals and increase the catalytic activity. The H2-TPR analysis confirmed that the presence of Ni lowered the reduction temperature of Co oxides in the bimetallic xNiyCo/SA catalyst compared to the monometallic Co/SA catalyst, which would increase the amount of metallic Co. Based on the product distribution, it could be proposed that the hydrogenation of DPE over catalyst 15Ni15Co/SA was mainly via the reaction path of “partial hydrogenation-hydrogenolysis-hydrogenation" process. The catalytic activity of catalyst15Ni15Co/SA could be recovered after regeneration. It also exhibited versatility for the cleavage of other CO bonds.

Two-dimensional carbon nanosheets loaded with NiCo bimetallic catalysts for efficient electrocatalytic reduction of nitrogen to ammonia

Ammonia, one of the most produced chemicals, is mainly produced by the Haber Bosch process, under high-temperature, high-pressure, and energy-intensive conditions. Therefore, electrocatalytic nitrogen reduction is an attractive alternative method under ambient conditions. In this paper, two-dimensional carbon nanosheets (CNS) are firstly prepared by a modified Hummer method, and then Co and Ni bimetal load on CNS are prepared by a hydrothermal method to investigate their electrocatalytic nitrogen reduction reaction (NRR) properties. CNS has a porous sheet structure, and the NiCo oxide nanoflower structure with zigzag folding grows on the surface of CNS, which is beneficial to improve the contact area of the catalyst with N2, increasing the number of active sites, and better improve the performance of N2 reduction NH3 synthesis. At −0.34 V, the NH3 yield reaches a maximum of 22.18 μg·h−1·mg−1, and the Faradaic efficiency (FE) is 4.50 %, both of which are about twice as high as that of pure CNS, which is superior to other metal-doped electrocatalysts used for N2 reduction. This study provides an effective method for the design of electrocatalysts with high N2 reduction performance for ammonia synthesis. The catalytic mechanism is further explored by the theoretical calculations of DFT.

Improvement of electrocatalytic properties of copper nanofoam modified by coral reef-like nickel-cobalt electrocatalyst for water splitting

Synthesis of a stable and efficient electrocatalyst for hydrogen evolution reaction (HER) using earth-abundant elements and inexpensive regents is essential to produce green H2 as an alternative to fossil fuels. In this study, a novel electrocatalyst has been developed using a Cu-foam substrate with a large surface area and electrochemically modified by Ni-Co bimetallic catalyst. A simple and effective two-step electrodeposition method has been applied using a solution of Ni and Co precursors to form NiCo@Cu-foam electrode. The SEM results indicated a porous structure for Cu-foam substrate with numerous active sites for the electrodeposition of Ni-Co electrocatalyst. The synergistic effect of Ni, Co, and Cu atoms with high conductivity and low overpotential has made NiCo@Cu-foam an excellent electrocatalyst. Remarkably, in 0.5 M H2SO4 acidic media, NiCo@Cu-foam electrode showed increased electrocatalytic activity to provide a current density of 100 mA.cm−2 compared to the corresponding values for Co@Cu-foam and Ni@Cu-foam electrodes at − 0.12, − 0.16, and − 0.19 V vs. RHE. Moreover, the fabricated catalyst showed a low Tafel slope of 67 mV.cm−1 and outstanding long-term stability for H2 evolution without considerable decrease at different overpotentials and current densities. The present study introduced an attractive candidate with improved performance for water splitting and clean energy production fabricated by inexpensive starting materials.