Nanosheet Catalyst Research Articles

The controllable synthesis of NiO/Ni/C nanosheets via pulsed plasma in ethylene glycol solution for oxygen evolution electrocatalysis.

NiO-based composites exhibit high catalytic activity for the oxygen evolution reaction (OER). Herein, high-performance NiO/Ni/C nanosheet catalysts were obtained by liquid-phase pulsed plasma (LPP), which was generated between two nickel electrodes in ethylene glycol (EG) solution by a homemade high-voltage pulse power supply. Melted nickel nanodrops were ejected from nickel electrodes which were bombarded by the energetic plasma. Simultaneously, high-temperature nickel nanodrops promoted the decomposition of the organics which were converted in the EG solution by the catalysis of LPP and formed hierarchical porous carbon nanosheets. Due to the high surface energy of the hierarchical porous carbon nanosheets, the spherical particles of Ni/NiO were adsorbed on the surface to compose the NiO/Ni/C composites. The pore size distribution of the composites could be controlled with different EG concentrations. When the EG concentration was 10 vol% (EG30), the composites possessed a H2 + H2 + H3 type pore size distribution and maximum active site area, leading to an exceptional OER activity (289.2 mV overpotential at 10 mA cm-2).

Ultralow ruthenium modification of cobalt metal-organic frameworks for enhanced efficient bifunctional water splitting.

Hydrogen economy has emerged as a promising alternative to the current hydrocarbon economy. It involves harvesting renewable energy to split water into hydrogen and oxygen and then further utilising clean hydrogen fuel for various applications. The rational exploration of advanced non-precious metal bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical for efficient water splitting. Herein, an ultralow Ru-modified cobalt metal-organic framework (CoRu0.06-MOF/NF) two-dimensional nanosheet array bifunctional catalyst was fabricated through a strategy under mild experimental conditions. The obtained CoRu0.06-MOF/NF exhibited excellent bifunctional electrocatalytic activity and stability in alkaline media, with low overpotentials of 37 and 181 mV and significant durability for more than 95 and 110 h toward the HER and OER at 10 mA cm-2, respectively. The experimental results showed that the two-dimensional nanoarray structure had a large specific surface area and abundant exposed active sites. Additionally, ultralow Ru modification optimized the electronic structure and improved the conductivity of the cobalt metal-organic frameworks, thereby reducing the energy barrier of the rate-limiting step and accelerating the water splitting reaction.

Massively synthesizable nickel-doped 1T-MoS2 nanosheet catalyst as an efficient tri-functional catalyst.

In this study, a nickel (Ni)-doped 1T-MoS2 catalyst, an efficient tri-functional hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) catalyst, was massively synthesized at high pressure (over 15 bar). The morphology, crystal structure, and chemical and optical properties of the Ni-doped 1T-MoS2 nanosheet catalyst were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ring rotating disk electrodes (RRDE), and the OER/ORR properties were characterized using lithium-air cells. Our results confirmed that highly pure, uniform, monolayer Ni-doped 1T-MoS2 can be successfully prepared. The as-prepared catalysts exhibited excellent electrocatalytic activity for OER, HER, and ORR owing to the enhanced basal plane activity of Ni doping and formidable active edge sites resulting from the phase transition to a highly crystalline 1T structure from 2H and amorphous MoS2. Therefore, our study provides a massive and straightforward strategy to produce tri-functional catalysts.

Electronic modulation of CoP nanosheets array by Zn doping as an efficient electrocatalyst for overall water splitting

A zinc-doped CoP nanosheet catalyst (Zn-CoP/CF) grown in situ on a cobalt foam substrate with a three-dimensional array structure, can effectively improve the electrocatalytic overall water splitting performance due to the gradual dissolution of Zn.

Fluorine and phosphorus atoms cooperated on an N-doped 3D porous carbon network for enhanced ORR performance toward the zinc–air batteries

A three-dimensional N-doped porous carbon nanosheet catalyst cooperated by fluorine and phosphorus atoms was prepared in this work, which showed high oxygen reduction performance in 0.1 M KOH and a power density of 138 mW cm−2 in zinc–air battery.

A highly loaded, excellent recyclable nanosheet catalyst Au@mesoporous SiO2

Gold@mesoporous silica nanosheet (Au@MSNS) catalyst was synthesized by one‐pot reduction of HAuCl4 with formaldehyde. Subsequent SiO2 recoating procedure was shown to reduce the average size of the loading Au nanoparticles, resulting in significantly improved catalytic activity of the modified Au@MSNSs against reduction of 4‐nitrophenol. Moreover, this procedure improves mechanical properties and reusability of the catalyst demonstrating superior turnover frequency of 91.954 × 10−3 mol g−1 h−1 in cyclic reaction.

Trace Mn-doped on highly dispersed Fe/Mn-SNC ultrathin carbon nanosheets for efficient oxygen reduction reaction

The design and development of non-noble metal carbon-based catalysts with efficient oxygen reduction activity remains a difficult problem. Here, Ultrathin two-dimensional carbon nano sheet catalyst Fe/Mn-SNC with rich pore structure doped with trace manganese was synthesized by simple sodium chloride template cracking method and freeze-drying method. Citric acid containing a large number of OH and COOH groups can provide multiple coordination sites for metal ions. In 0.1 M KOH solution, the Fe/Mn-SNC catalyst performed better than Pt/C in terms of ORR performance (E1/2 was 0.920 V vs RHE) and endurance (E1/2 fell roughly 5 mV after 10,000 cycles). The reaction path of the Fe/Mn-SNC was calculated through DFT calculation. It was found that a small amount of Mn doping would reduce the adsorption energy of OH*, the last step in ORR reaction, which was conducive to OH* falling off from the catalyst surface, reducing the potential barrier required for the reaction, and improving its ORR activity. This research offers fresh perspectives on the development of enhanced energy conversion as well as the design and synthesis of high-performance ORR catalysts.

Novel core–shell heterojunction photocatalytic wire mesh for efficient ciprofloxacin degradation under visible light

In order to solve the problems of easy recombination of electron–hole pairs, low solar energy utilization efficiency and difficult reuse of catalyst, a core–shell α–Fe2O3/Bi2MoO6@304SS heterojunction photocatalytic was synthesized and successfully immobilized on the 304 stainless steel (304SS) wire mesh. The result featured a flower–like particles assembled by a nanosheet catalyst uniformly distributed on the surface of the α–Fe2O3 shell, and showed high adsorption and visible–light photocatalytic activity towards ciprofloxacin (CIP). The CIP degradation efficiencies of 96 % and 92 % in the presence of visible light from a 40 W LED lamp and direct sunlight, respectively. Moreover, the photocatalytic mesh exhibited good structure stability and recycling performance. As determined, a built–in the electric field generated by the heterojunction reduced the recombination probability of electron–hole pairs, and significantly improved photocatalytic activity. Additionally, the possible electron migration mode in the heterojunction interface is proposed, the photocatalytic mechanism is elucidated, and possible degradation pathways of CIP are analyzed. With these unique features, the synthesis of photocatalytic mesh could be easily applied in water environment restoration and wastewater treatment systems.

Rationally designed hierarchical carbon supported CuO nano-sheets for highly efficient electroreduction of CO2 to multi-carbon products

Electrochemical reduction of CO2 to value-added products is a promising path to mitigate CO2 emissions and achieve renewable energy conversion and storage. Cu-based electrocatalysts can catalyze electrochemical conversion of CO2 to multi-carbon products, however, low catalytic activity and selectivity have hindered the practical applications of this technology. Rationally designing the structure of catalysts for an improved catalytic performance is of vital importance. Here, we reported a hierarchical phenol formaldehyde resin carbon supported CuO nano-sheets (CuO/PFRC) catalyst for enhanced CO2 electroreduction to multi-carbon products. Compared with CuO nano-sheets (CuO) and commercial VXC-72r carbon black supported CuO nano-sheets (CuO/XVC), CuO/PFRC showed an enhanced catalytic activity towards multi-carbon products (mainly ethylene). The electrochemical measurements exhibited an ethylene Faradaic efficiency of 47.2 % at − 0.64 V (vs. RHE) with a high partial current density of 599 mA cm−2, which outperformed most previously reported studies. We proposed that the 3D hierarchical structure of CuO/PFRC could facilitate electron transfer process, thus promoting the catalytic activity. Further study uncovered that the hierarchical CuO/PFRC had higher CO2 adsorption capacity than control samples, which may favor to form a higher local CO2 concentration environment during CO2 electroreduction reaction and further facilitate catalytic activity promotion.

Photocatalytic Degradation of Tetracycline Using Visible-light-driven Porous g- C3N4 Nanosheets Catalyst

Photocatalytic Degradation of Tetracycline Using Visible-light-driven Porous g- C3N4 Nanosheets Catalyst

Ni-Fe-Al LDH derived Ni[sbnd]Fe nanosheet for green diesel production from lipid hydrotreatment

In order to deal with the deficiency of active sites in Ni catalyst, NiFe nanosheet (Ni-Fe/Al2O3-NS) catalyst was synthesized by using Ni-Fe-Al LDH as the precursor. The catalyst was further utilized in the lipid hydrotreatment for green diesel production. With a lamellar structure and large Ni loading (more than 60%), the Ni-Fe/Al2O3-NS catalyst possessed abundant Ni sties with high dispersion, large surface area, and strong acidity. Moreover, in Ni-Fe/Al2O3-NS the highly active Ni3Fe phase was formed, which promoted the decarbonylation route in hydrotreatment. The Ni-Fe/Al2O3-NS catalyst achieved 98.7% conversion with 98.1% alkane yield in oleic acid hydrotreatment under very mild conditions (220 °C, 2 MPa of hydrogen pressure, 3 h). The catalytic performance of Ni-Fe/Al2O3-NS was much higher than traditional Ni-Fe/Al2O3 and other catalysts reported in current related studies.

High-Performance Ternary NiCoMo Electrocatalyst with Three-Dimensional Nanosheets Array Structure.

Oxygen evolution reaction is a key process in hydrogen production from water splitting. The development of non-noble metal electrode materials with high efficiency and low cost has become the key factor for large-scale hydrogen production. Binary NiCo-layered double hydroxide (LDH) has been used as a non-noble metal electrocatalyst for OER, but its overpotential is still large. The microstructure of the catalyst is tuned by doping Mo ions into the NiCo-LDH/NF nanowires to form ternary NiCoMo-LDH/NF nanosheet catalysts for the purpose of enhancing the active sites and reducing the initial overpotential. Only 1.5 V (vs. reversible hydrogen electrode (RHE), ≈270 mV overpotential) is required to achieve a catalytic current density of 10 mA cm-2 and a small Tafel slope of 81.46 mV dec-1 in 1 M KOH solution, which manifests the best performance of NiCo-based catalysts reported up to now. Electrochemical analysis and micro-morphology show that the high catalytic activity of NiCoMo-LDH/NF is attributable to the change of the microstructure. The interconnected nanosheet arrays have the obvious advantages of electrolyte diffusion and ion migration. Thus, the active sites of catalysts are significantly increased, which facilitates the adsorption and desorption of intermediates. We conclude that NiCoMo-LDH/NF is a promising electrode material for its low cost and excellent electrocatalytic properties.

Ni2P Nanoparticle-Inserted Porous Layered NiO Hetero-Structured Nanosheets as a Durable Catalyst for the Electro-Oxidation of Urea.

The electro-oxidation of urea (EOU) is a remarkable but challenging sustainable technology, which largely needs a reduced electro-chemical potential, that demonstrates the ability to remove a notable harmful material from wastewater and/or transform the excretory product of humans into treasure. In this work, an Ni2P-nanoparticle-integrated porous nickel oxide (NiO) hetero-structured nanosheet (Ni2P@NiO/NiF) catalyst was synthesized through in situ acid etching and a gas-phase phosphating process. The as-synthesized Ni2P@NiO/NiF catalyst sample was then used to enhance the electro-oxidation reaction of urea with a higher urea oxidation response (50 mA cm−2 at 1.31 V vs. RHE) and low onset oxidation potential (1.31 V). The enhanced activity of the Ni2P@NiO/NiF catalyst was mainly attributed to effective electron transport after Ni2P nanoparticle insertion through a substantial improvement in active sites due to a larger electrochemical surface area, and a faster diffusion of ions occurred via the interactive sites at the interface of Ni2P and NiO; thus, the structural reliability was retained, which was further evidenced by the low charge transfer resistance. Further, the Ni2P nanoparticle insertion process into the NiO hetero-structured nanosheets effectively enabled a synergetic effect when compared to the counter of the Ni2P/NiF and NiO/NiF catalysts. Finally, we demonstrate that the as-synthesized Ni2P@NiO/NiF catalyst could be a promising electrode for the EOU in urea-rich wastewater and human urine samples for environmental safety management. Overall, the Ni2P@NiO/NiF catalyst electrode combines the advantages of the Ni2P catalyst, NiO nanosheet network, and NiF current collector for enhanced EOU performance, which is highly valuable in catalyst development for environmental safety applications.

Hierarchical leaf-like alumina-carbon nanosheets with ammonia water modification for ethanol dehydration to ethylene

A hierarchical leaf-like alumina-carbon nanosheet catalyst was prepared by a chelate-assisted co-assembly method to improve the catalytic behavior of ethanol dehydration reaction, based on the chemical etching effect of ammonia water. The uniformly dispersed leaf-like nanosheet structure possessed a relatively large specific surface area and exposed more active sites, which could promote the ethanol dehydration reaction. This catalyst was promising to obtain a higher catalytic behavior (conversion of 98.3 % and ethylene selectivity of 97.0 %) than the sample without ammonia water modification (conversion of 63.2 % and ethylene selectivity of 46.7 %) at 450 ℃. The addition of ammonia water played an essential role in influencing the formation of the leaf-like nanosheet structure and the generation of Brönsted acid active sites, which remarkably promoted the proceed of ethanol dehydration. Importantly, a direct relationship was observed between the nanosheet thickness and the alumina content. The best catalytic activity with TOF of 361.8 h−1 was obtained when the Al loading of 13.9 wt%, attributed to the suitably balanced weak/moderate acidic active sites ratio of ∼ 4.37. In-situ FTIR spectra of ethanol dehydration reaction clearly confirmed that ethanol was first converted to the intermediate product diethyl ether and then subsequently decomposed to ethylene at a higher temperature. The catalyst also maintained a good recyclability upon time on stream of 144 h at 450 ℃. This work provides an alternative way of developing non-noble metal catalyzing ethanol dehydration to ethylene.

Interfacial oxidation using potassium ferrate to fabricate self-supported hydrophilic NiFe-LDH nanoarrays for overall water splitting at high current density

The preparation of NiFe layered double hydroxide (NiFe-LDH)-based efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through eco-friendly and convenient methods remains challenging. To overcome this, herein, we employed a novel one-step hydrothermal synthesis strategy by exploiting the strong oxidisability of potassium ferrate, which allows the oxidisation of the Ni foam (NF) surface, to obtain self-supporting, oversized, and hydrophilic NiFe-LDH nanosheet arrays. Because of the advantageous self-supporting structure, satisfactory hydrophilicity, excellent conductivity of the NF substrate as well as the strong interaction and synergistic optimisation of Ni and Fe bimetallic active centres, the catalytic performance of the NiFe-LDH was significantly enhanced. The optimised NiFe layered double hydroxide nanosheet array catalyst grown on nickel foam with 3.5 mmol K2FeO4 added [NiFe-LDH/NF-3.5] required overpotentials of only 75 and 223 mV (for the HER) and 249 and 303 mV (for the OER) to achieve 10 and 100 mA cm−2, respectively. An alkaline electrolyser based on NiFe-LDH/NF-3.5 achieved these current densities at battery voltages as low as 1.57 and 1.75 V. At a high current density (500 mA cm−2), the catalyst was also successfully operable for 230 h, demonstrating its remarkable stability. Furthermore, DFT calculation results verified that the adsorption energy of NiFe-LDH/NF-3.5 was suitable for H and OH. Thus, this study not only proposes an efficient strategy for NiFe-LDH synthesis but also promotes the development of non-precious-metal catalysts for practical applications.

The role of Ce doping on the activity of La2O2CO3 nanosheets catalysts in synthesis of dimethyl carbonate from propylene carbonate and methanol

Dimethyl carbonate (DMC) production from the transesterification reaction of propylene carbonate (PC) and methanol is an eco-friendly and economical process with propylene glycol (PG) as the high value-added co-product. We report herein the synthesis of Ce-doped La2O2CO3 nanosheets (La1Cex) with varying Ce contents through a solvothermol method. La1Ce0.15 catalyst exhibits superior catalytic performance in the production of DMC by the transesterification of methanol and PC. A remarkable improvement in PC conversion (> 85%) and DMC selectivity (> 98%) can be attributed to an increase in surface O2− base sites caused by increased oxygen interstitials and vacancies through Ce doping.

Catalytic degradation of benzene over non-thermal plasma coupled Co-Ni binary metal oxide nanosheet catalysts

Non-thermal plasma (NTP) has been demonstrated as one of the promising technologies that can degrade volatile organic compounds (VOCs) under ambient condition. However, one of the key challenges of VOCs degradation in NTP is its relatively low mineralization rate, which needs to be addressed by introducing catalysts. Therefore, the design and optimization of catalysts have become the focus of NTP coupling catalysis research. In this work, a series of two-dimensional nanosheet Co-Ni metal oxides were synthesized by microwave method and investigated for the catalytic oxidation of benzene in an NTP-catalysis coupling system. Among them, Co2Ni1Ox achieves 60% carbon dioxide (CO2) selectivity (SCO2) when the benzene removal efficiency (REbenzene) reaches more than 99%, which is a significant enhancement compared with the CO2 selectivity obtained without any catalysts (38%) under the same input power. More intriguingly, this SCO2 is also significantly higher than that of single metal oxides, NiO or Co3O4, which is only around 40%. Such improved performance of this binary metal oxide catalyst is uniquely attributed to the synergistic effects of Co and Ni in Co2Ni1Ox catalyst. The introduction of Co2Ni1Ox was found to promote the generation of acrolein significantly, one of the key intermediates found in NTP alone system reported previously, suggest the benzene ring open reaction is promoted. Compared with monometallic oxides NiO and Co3O4, Co2Ni1Ox also shows higher active oxygen proportion, better oxygen mobility, and stronger low-temperature redox capability. The above factors result in the improved catalytic performance of Co2Ni1Ox in the NTP coupling removal of benzene.

A new aminobenzoate-substituted s-triazin-based Zr metal organic frameworks as efficient catalyst for biodiesel production from microalgal lipids

In order to solve problems that large molecules of microalgal lipids were difficult to access active sites in micropore structures of traditional metal organic frameworks (MOF), a novel two-dimensional nanosheet catalyst (aminobenzoate-substituted s-triazin-based Zr metal organic frameworks, Zr-TATAB) that exposed more active sites with stronger acidity was synthesized through replacement of trimesate linker in water/acid-resistant Zr-based MOF-808 with 4,4 ́,4 ́ ́-s-triazine-1,3,5-triyltri-p-aminobenzoate (H3TATAB) to promote catalytic conversion efficiency of microalgal lipids to biodiesel. The binding energy of Zr increased by 0.2 eV due to electronic shift caused by triazine ring and imine groups in H3TATAB ligand, which led to more exposed Zr4+ active sites in Zr-TATAB catalyst. Due to increase of charge on crystal edges, dissociation of terminal hydroxyl groups was inhibited and Coulomb repulsion was increased. Therefore, Zr-TATAB catalyst possessed higher dispersion to avoid from pore blocking and catalytic deactivation, which enhanced recycling performance of catalyst. Compared with MOF-808, the total number of acid and base sites in Zr-TATAB catalyst increased from 6.0 mmol g−1 to 8.0 mmol g−1, while strength of acid sites increased with an increased ammonia desorption temperature by 150 °C, which led to an increased catalytic conversion efficiency of microalgal lipids to biodiesel to 98.2%.

Enhanced oxygen reduction of porous N-doped carbon nanosheets with graphitic N and defects obtained from coal-based graphene quantum dots

Metal-free carbon-based electrocatalysts for oxygen reduction reaction (ORR) have received considerable attention owing to their abundance and low cost. However, designing carbon-based electrocatalysts with excellent performance in a facile manner remains a challenge. In this work, porous nitrogen-doped carbon nanosheet (PNCNs) catalysts with high contents of graphitic N and defects were readily prepared via a simple self-doping method, in which coal-based graphene quantum dots (GQDs) were used as the carbon and nitrogen resource. Based on the results, PNCNs-900 (obtained at 900 °C) displayed good ORR performance, with a half-wave potential (E1/2) of 0.80 V. It also exhibited high stability and methanol tolerance compared with commercial Pt/C. Experimental investigations and theoretical calculations prove that the increased ORR electrocatalytic activity of PNCNs-900 is due to the synergistic effect of a large number of defects and graphitic N. Furthermore, its higher electrocatalytic activity for ORR also benefits from the porous lamellar structure, which facilitates the mass transfer process. This study offers a novel approach for developing effective ORR catalysts and for the high value-added utilization of coal resources.

Heterogeneous cobalt-iron phosphide nanosheets formed by in situ phosphating of hydroxide for efficient overall water splitting

Transition metal phosphides (TMPs) have emerged as one of the most promising electrocatalysts toward water decomposition because of exceptional catalytic properties and abundant reserves. Herein, we successfully construct an unique CoP3/Fe2P nanosheet catalyst grown on Ni foam (CoP3/Fe2P@NF NSs) via a successive solvothermal-phosphating strategy for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It should be emphasized that abundant heterointerfaces and lots of nanopores are formed by in-situ phosphating CoFe layered double hydroxides (CoFe-LDHs) precursor. Specifically, the redistribution of electrons at heterogeneous interfaces provides more active sites for reactant molecules or intermediates, and abundant nanopores on the nanosheets facilitate escape of resulting gas, thus releasing active sites in time. Density functional theory (DFT) calculation also proves that CoP3-Fe2P heterointerfaces can further optimize hydrogen adsorption energy (ΔGH*) to effectively reduce free energy barrier. Thus, the CoP3/Fe2P@NF-2 catalyst presents extraordinary electrocatalytic performance towards HER and OER with overpotentials of 81 mV and 236 mV at 10 mA cm−2. As an encouraging result, it provides a low voltage of 1.53 V at 20 mA cm−2 and satisfactory cycling stabilization of over 28 h, comparable to most reported catalysts. This work affords a promising approach for synthesis of binary and above transition metal phosphides.