Nanoparticle Catalysts Research Articles

A “pre-constrained bimetallic” strategy for the preparation of efficient synergistic electrocatalytic hydrogen evolution catalysts

A micro-sized bimetallic nanoparticles (NPs) catalyst that anchors a mixture of Co and Pd atoms onto a porous nitrogen-doped carbon (NC) framework for electrocatalysis of hydrogen evolution reaction (HER). Programmable metal-porphyrin ligands serve as building blocks for attaching bimetallic sites (consisting of Co and Pd) in metal-organic frameworks for decentralized anchoring before pyrolysis. Experimental studies have shown the interaction between Pd and Co in Co20/Pd20-NC results in electron depletion near Co and electron accumulation near Pd, respectively. Therefore, there is an asymmetric local electron density distribution on the bimetallic site of Co20/Pd20-NC, which improves the activity of the catalyst. To achieve a current density of 10mA·cm-2 in both acidic and alkaline conditions, the Co20/Pd20-NC exhibits noteworthy HER characteristics with overpotentials of 23 and 52mV, respectively. The Co20/Pd20-NC prepares in this study which shows good characteristics in the process of electrocatalytic hydrogen evolution, and has a good application prospect.

Synthesis and optimization of Pt nanoparticle catalyst supported on heterogeneous composite Mo2C-N-C for acidic direct methanol fuel cell anodes

Molybdenum carbide (Mo2C) has similar d-band characteristics to platinum (Pt), so it has a similar catalytic activity to Pt. It can be used as a catalyst support or co-catalyst in the anode of direct methanol fuel cells (DMFC). The unique hexagonal crystal system structure of Mo2C is beneficial for improving the overall performance of the catalyst when combined with N-doped carbon (N-C). When Pt is loaded onto the Mo2C-N-C support, the synergistic effect between Mo2C-N-C and Pt makes the catalyst exhibit higher activity and stability in the methanol oxidation reaction. In this study, a high-quality Mo2C-N-C support was synthesized using stripped g-C3N4 as a self-sacrificing template, followed by the preparation of Pt/Mo2C-N-C catalyst via microwave-assisted glycol reduction. In acid media, the optimized Pt/Mo2C-N-C catalyst exhibited improved methanol oxidation reaction (MOR) activity and robust durability, the methanol oxidation current density reached 1.74 times that of commercial Pt/C, which was prepared under the same conditions, demonstrating the catalyst’s superior methanol oxidation activity.

Removal of bisphenol A through peroxymonosulfate activation with N-doped graphite carbon spheres coated cobalt nanoparticles catalyst: Synergy of nonradicals

Removal of bisphenol A through peroxymonosulfate activation with N-doped graphite carbon spheres coated cobalt nanoparticles catalyst: Synergy of nonradicals

Performance constraints of high temperature polymer electrolyte membrane fuel cells by varying the Pt/C ratio of the catalyst

Electrodes prepared from catalysts with Pt weight percentages on the carbon support (Pt/C nanoparticles) ranging from 10 up to 60 wt% are used as cathodes of membrane electrode assemblies (MEAs) and tested in high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). For each Pt/C percentage in the catalyst, the cathode Pt-loading (which become proportional to the thickness of the electrode formed by the catalyst nanoparticles) is stepwise scanned from low to high loadings. Results show that when the Pt load increases, the MEA performance (measured by its power density at 0.6 V) rises initially (due to the increase in the number of active sites in the cathode) up to a maximum value limited by the mass transport of oxygen, associated to an optimum Pt-loading (different for each Pt/C ratio). Noteworthy, the peak performance is significantly different depending on the catalyst used (60 > 40 >> 20 > 10 wt% Pt/C), a fact that restricts the catalyst choice according to the performance required by the application. Furthermore, higher amounts of Pt in the cathode lead to a large catalyst waste as the FC performance even decreases as the cathode thickness increases.

Experimental assessment of catalytic biofuel effect on performance and exhaust emission of diesel engine

The present experiment is to analyze the effect of blended biodiesel of chicken fat CF10 (10% chicken fat and 90% diesel), waste cooking oil WC10 (10% waste cooking oil and 90% diesel), and combined chicken fat with waste cooking oil CF&WC10 (5% chicken fat + 5% waste cooking oil and 90% diesel) on the performance of diesel engine. The experiment is conducted at a constant compression ratio of 17, mixing 50 ppm alumina alfa (Al2O3-α) catalyst nanoparticles in each blend. The performance of biodiesel is analyzed at 25%, 50%, 75%, and 100% load conditions and is compared with pure diesel. The results show that the brake torque (BT) and brake power of CF&WC10 were found to be 22.48 Nm and 3.58 kW at full load conditions. However, the indicated thermal efficiency and BTE of CF&WC10 are at full loading conditions of 52.45% and 26.78% respectively. Because the supply of A/F ratio is 18.81, at full load condition and also lowering the brake specific fuel consumption up to 0.32 kg/kWh. Therefore, optimization of both performance and exhaust emission of an engine depends on BTE and NOx as well as HC emissions. Hence, from the emissions reduction point of view, CF&WC10 has lower emissions while achieving brake thermal efficiency similar to diesel fuel. The novelty of research shows CF&WC10 leads to enhanced performance of diesel engine compared to pure diesel fuel.

Pt Nanoparticles on Multi-Walled Carbon Nanotubes with High CO Tolerance for Methanol Electrooxidation.

Anode catalysts are important for direct methanol fuel cells (DMFCs) of energy conversion. Herein, we report a novel strategy by ethylene glycol-based deep eutectic solvents (EG-DESs) for the fabrication of a multi-walled carbon nanotubes (MWCNTs)-supported Pt nanoparticles catalyst (referred to as Pt/CNTs-EG-DES). The Pt/CNTs-EG-DES catalyst provides an increased electrochemically active surface area (ECSA) and shows remarkably improved electrocatalytic performance towards methanol oxidation reaction compared to Pt/CNTs-W (fabricated in water) and commercial Pt/C catalysts. The improved performance is attributed to the generation of more Pt-O bonds which change the electronic states of the Pt atoms and the special node structure that obtains more active sites for a high CO resistance. This study suggests an effective synthesis strategy for Pt-based electrocatalysts with high performance for DMFC applications.

Engineering Chemical and Catalytic Activity of Metal Surface Sites by Controlling Strain and Ligand Effects in Nonmodel Nanoparticle Catalysts

Engineering Chemical and Catalytic Activity of Metal Surface Sites by Controlling Strain and Ligand Effects in Nonmodel Nanoparticle Catalysts

“Sunlight-driven catalytic degradation of MB dye and multi-cycle Re-usability analysis of Cu2-xSe nanoparticles”

One of the best ways to remove organic dyes based contaminant from water resources and industrial waste water is the sunlight driven photo-catalytic degradation method. The theme of the present investigation is the photocatalytic degradation of methylene blue (MB) dye using economically produced Cu2-XSe nanoparticles (NPs) catalyst under solar radiations. The Cu2-XSe NPs crystallized in the cubic structural phase with an average crystallite size around 19 nm. The direct band gap was found to be 2.1 eV. The PL spectra and corresponding CIE diagram show the Cu2-xSe NPs emitted yellow color. The SEM micrographs show that the small grains staked over others to form large grains or patches. The FTIR and EDX spectra confirmed the formation of Cu2-XSe NPs. The obtained optimum photocatalytic degradation efficiency for Cu2-XSe NPs is 90.3 %. For first cycle analysis. The pseudo-first order and second order models were used to analyze the kinetic data of Cu2-XSe NPs for varying concentrations. The multiple-cycle degradation analysis by catalyst of MB dye in one day spam for continuous four cycles were also analysed and discussed. The sun light driven multi-cycle catalytic degradation confirms the re-usability of Cu2-xSe NPs for the treatment of industrial waste water and other contaminated water bodies for the survival of aquatic life and for saving environment.

Electronic effect in bromide-modified noble metal catalysts promotes highly stable and selective hydrogenation

Halides with strong affiliation to metals are traditionally viewed as positions in heterogeneous catalysis. This study introduces a method to enhance the selective hydrogenation performance of noble metal nanoparticle catalysts (Pd, Pt, and Rh hosted on N-doped carbon, SiO2, and Al2O3) by gas-phase bromination with 1-bromooctane. Brominated Pd catalysts, particularly those supported on N-doped carbon, show significant improvements in total butene selectivity and stability in butadiene hydrogenation reactions, displaying >97.5 % selectivity to total butenes at complete conversion with 50 h stable performance even at excessive H2 (H2:butadiene = 50) and a high temperature of 473 K. Comprehensive characterizations coupled with density functional theory calculations reveal that bromide species enhance selective hydrogenation by preferentially adsorbing at stepped Pd sites, altering reaction kinetics and preventing over-hydrogenation. Bromination influences reactant and intermediate adsorption, leading to increased competitive adsorption compared to pristine catalysts. Chemisorption studies on butadiene and 1-butene support altered kinetic behaviors post-bromination. X-ray photoelectron spectroscopy analysis demonstrate an increase in surface Pdδ+ species, owing to the electron-pulling character of nearby adsorbed bromide. In situ diffuse reflection infrared Fourier transform spectroscopy with CO probe molecules confirms Br species adsorption at unsaturated Pd sites. Overall, the study provides an effective approach to tuning the electronic properties of metal catalysts and highlights the positive impact of bromination on improving the hydrogenation performance.

Highly stable and active catalyst in fuel cells through surface atomic ordering.

Shape-controlled alloy nanoparticle catalysts have been shown to exhibit improved performance in the oxygen reduction reaction (ORR) in liquid half-cells. However, translating the success to catalyst layers in fuel cells faces challenges due to the more demanding operation conditions in membrane electrode assembly (MEA). Balancing durability and activity is crucial. Here, we developed a strategy that limits the atomic diffusion within surface layers, fostering the phase transition and shape retention during thermal treatment. This enables selective transformation of platinum-iron nanowire surfaces into intermetallic structures via atomic ordering at a low temperature. The catalysts exhibit enhanced MEA stability with 50% less Fe loss while maintaining high catalytic activity comparable to that in half-cells. Density functional calculations suggest that the ordered intermetallic surface stabilizes morphology against rapid corrosion and improves the ORR activity. The surface engineering through atomic ordering presents potential for practical application in fuel cells with shape-controlled Pt-based alloy catalysts.

Fuel Cell Catalyst Layers with Platinum Nanoparticles Synthesized by Sputtering onto Liquid Substrates.

Platinum (Pt) nanoparticles are widely used as catalysts in proton exchange membrane fuel cells. In recent decades, sputter deposition onto liquid substrates has emerged as a potential alternative for nanoparticle synthesis, offering a synthesis process free of contaminant oxygen, capping agents, and chemical precursors. Here, we present a method for the synthesis of supported nanoparticles based on magnetron sputtering onto liquid poly(ethylene glycol) (PEG) combined with a heat-treatment step for attachment of nanoparticles to a carbon support. Transmission electron microscopy imaging reveals Pt nanoparticle growth during the heat-treatment process, facilitated by the carbon support and the reducing properties of PEG. Following the heat treatment, a bimodal size distribution of Pt nanoparticles is observed, with sizes of 2.5 ± 0.8 and 6.7 ± 1.8 nm, compared to 1.8 ± 0.4 nm after sputtering. Synthesized Pt nanoparticles display excellent specific and mass activities for the oxygen reduction reaction, with 1.75 mA/cm2 Pt and 0.27 A/mgPt respectively, measured at 0.9 V vs the reversible hydrogen electrode. The specific activities reported herein outperform literature values of commercial Pt/C catalysts with similar loading and are on par with values of bulk Pt and mass-selected nanoparticles of comparable size. Also, the mass activities agree well with the literature values. The results provide new insights into the growth processes of SoL-synthesized carbon-supported Pt catalyst nanoparticles, and most crucially, the high performance of the synthesized catalyst layers, along with the possibility of nanoparticle growth through a straightforward heat-treatment step at relatively low temperatures, offer a scalable new approach for producing fuel cell catalysts with more efficient material utilization and new material combinations.

Regulating the location relationship between Cu nanoparticles and Pt atoms to enhance the catalytic hydroisomerization performance: Together or apart?

Single atom catalysts have been recently reported as the efficient catalysts for hydroisomerization compared to the conventional nanoparticle catalyst. Despite the fascinating advantage in enhancing the metal activity or reducing the catalyst cost, the long-term stability of the single atom catalyst seemed not that satisfactory, especially when reacting under atmospheric pressure. Herein, Pt single atom catalysts were combined with Cu nanoparticles by different means to explore a new way to improve the catalytic performance. Cu nanoparticles were located away from Pt sites to form a binary catalyst, or acted as the support of Pt atoms to form a single atom alloy (SAA) catalyst. With the binary catalyst Pt1–0.1Cu@CS, the conversion of the n-heptane after time on stream of 50 h increased to 70.3 %, higher than Pt1@CS (47.3 %). Besides, excessive Cu nanoparticles in the binary catalyst were found rather harmful to the catalysis instead. However, the SAA catalyst Pt1Cu@SAPO-11 showed a poor activity in hydroisomerization compared to Pt1@CS, indicating that the alloy structure should go against the activation of reactant. The roles of Pt atoms and Cu nanoparticles in different catalysts were discussed in detail. The reaction mechanism of hydroisomerization was refined with the different functions of the dual metal sites. This work might be instructive for the design of single atom catalysts combined with metal nanoparticles.

Bioinspired Synthesis of Novel Different Nanoparticles and its Utility in Biodiesel and Animals Applications

Because of its ability to speed up the reaction, the catalyst is critical to its success. Most catalysts are either homogeneous or heterogeneous. It has been shown that utilizing a heterogeneous catalyst, which is easier to remove from the product after the reaction has been finished. Because of the large surface area of the Nano-catalyst results in high catalytic efficiency. To enhance the performance of catalysts a range of various types of support materials have been used. SO42--ZnO and So42-/TiO active acid catalyst was prepared and characterized. ZnO nanoparticles catalyst synthesized by precipitation of zinc nitrate for comparison with supported catalyst. Sulphated zinc oxide (SO42--ZnO) and sulphated titania (SO42-/TiO) catalysts were synthesized using impregnation methods, to test their efficacy in biodiesel production. Various waste oils from different wastes such as mutton or beef tallow, chicken fat, and methanol are preferred to use during the esterification of waste animal fat oils using solid acid catalysts to produce biodiesel. Biodiesel synthesis generates a substantial amount of glycerol as a byproduct. Effect of optimum parameters such as temperature 60 degree centigrade (°C) shown 90% yield, time 1 hour resulted in 85% yield, catalyst dose 2wt% resulted in 80% yield, stirring speed 250rpm resulted in 80% yield, methanol to oil ratio12:1 resulted as 85.5% yield for transesterification of waste fat oil. It is valuable that the supported acid catalysts showed more yield than simply synthesized ZnO nanocatalyst similarly sulphated zinc oxide showed more FAME yield than sulphated titania.

Ru Nanoparticles Encapsulated by Defective TiO2 Boost the Hydrogen Oxidation/ Evolution Reaction.

The development of efficient and durable electrocatalysts for the alkaline hydrogen oxidation/evolution reaction is crucial for anion exchange membrane fuel cells/water electrolyzers. However, designing such electrocatalysts poses a challenge due to the need for optimizing various adsorbates. Herein, highly dispersed Ru nanoparticles catalysts is reported encapsulated and supported by defective anatase phase of titanium dioxide (named as Ru NPs/def-TiO2(A)) for boosting hydrogen-cycle electrocatalysis with robust anti-CO-poisoning in alkaline conditions. The Ru NPs/def-TiO2(A) achieves a high-quality activity of 7.65 A mgRu -1, which is 23.2 and 9.5-fold higher than commercial Ru/C and Pt/C in alkaline HOR. Moreover, this catalyst exhibits an outstanding overpotential of 21mV at 10mAcm-2 in alkaline HER. Hydrogen underpotential deposition (Hupd) and CO stripping experiments demonstrate that Ru NPs/def-TiO2(A) has the optimized H*, OH*, and CO* adsorption strength, enabling the Ru NPs/def-TiO2(A) catalyst to display excellent and robust HOR/HER performance under alkaline conditions. Using density functional theory calculations, the enhanced HOR performance mechanism for the Ru NPs/def-TiO2(A) catalyst originates from the TiO2 step face in contact with the Ru nanoparticles, indicating that the kinetics of water formation are considerably more favorable at the Ru NPs/def-TiO2(A) interface.

Magnetic Induction Heating-Driven Rapid Cold Start of Ammonia Decomposition for Hydrogen Production.

The advantages of ammonia as a hydrogen carrier have led to proposals for on-site hydrogen production through its decomposition. Rapid cold start of ammonia decomposition is crucial for applications such as ammonia-powered vehicles, but conventional heating methods are challenged by the high decomposition temperature of ammonia. In this study, we successfully achieved the rapid cold start of ammonia decomposition using Co nanoparticle catalysts driven by magnetic induction heating, demonstrating excellent catalytic performance and stability. The magnetic induction heating-driven ammonia decomposition system was integrated with a hydrogen fuel cell, proving its ability to achieve the cold start of ammonia decomposition within 10 s, as demonstrated by comparative experiments using 75% H2-25% N2 from a gas cylinder as the control. This study provides a deeper understanding of hysteresis heating catalysis, promoting the practical use of ammonia as a hydrogen carrier for rapid hydrogen production in the energy industry.

Direct Synthesis of Artificial Esterase through Molecular Imprinting Using a Substrate-Mimicking Acylthiourea Template.

Most reported artificial esterases hydrolyze only activated esters. We here report a one-pot synthesis of artificial esterases via molecular imprinting. An acylthiourea template hydrogen bonds with 4-vinylbenzoic acid and coordinates to a polymerizable zinc complex inside a cross-linkable surfactant micelle. Double cross-linking of the micelle yields a polymeric nanoparticle catalyst that mimics a metalloenzyme to activate a water molecule for nucleophilic attack on the bound ester. The catalyst hydrolyzes both activated and unactivated esters under mild conditions with selectivity.

Hydrodeoxygenation of guaiacol over modified coconut carbon supported Ni nanoparticles catalysts under alkaline condition

The efficient utilization of lignin from the papermaking black liquor has attracted interest due to its carbon-neutral value and industrial application. This work illustrates a simple support-phosphate-pretreatment strategy to develop superdispersed Ni species in activated carbon (AC) to enhance the hydrodeoxygenation (HDO) reactions of the lignin model compound guaiacol into biohydrocarbons under alkaline conditions. For the first time, sodium polyphosphate was applied as a pretreatment agent for coconut carbon in the synthesis of carbon-supported Ni catalysts. Superdispersed Ni nanoparticles were achieved on Ni/NaPnOAC with a particle size of 2.5 nm, which was much smaller than that on unmodified Ni/C (13.1 nm). The characterization results and reactions revealed that the P−O that formed served as anchoring sites for the Ni species and strengthened the interaction between the Ni species and support (SMSI), which resulted in significantly improved dispersion of the Ni metal sites and, thus, a nearly 6-fold greater yield of hydrocarbons was obtained on Ni/NaPnOAC (58.1 %) than on Ni/C (10.1 %). In addition, compared with Ni2P/NaPnOAC and NiS/NaPnOAC, Ni/NaPnOAC exhibited higher HDO activity, especially higher direct deoxygenation (DDO) activity and higher benzene yield, reducing hydrogen consumption during the HDO reaction.

Boosting low-temperature NH3-SCR performance via mixed-valence cobalt dual active sites

Nitrogen oxides (NOx) have become a critical environmental concern, necessitating the development of highly efficient catalysts for temperature which is lower than 300 °C. Selective catalytic reduction with NH3 (NH3-SCR) is a process where ammonia is the reducing agent for selective catalytic reduction of nitrogen oxides in exhaust gases. The mechanism-property relationship between catalytic active sites and low-temperature denitrification efficiency, however, remains unclear. In this study, we synthesized a series of cobalt-modified nanoparticle catalysts using a scalable citric acid sol-gel method and conducted comprehensive characterizations. Our findings indicate that an optimal cobalt doping rate significantly enhances catalytic activity due to the synergistic effects of reduced nanoparticle size and the dual active sites of Co0/Co2+. Specifically, at a cobalt doping ratio of 1.0, the catalyst demonstrates peak SCR activity, achieving 85.5% NOₓ conversion at 120 °C and complete conversion at 150 °C. These cobalt-modified nanoparticle catalysts feature high deposition of doped Co ions on their surfaces, predominantly as metallic cobalt and CoOx nanoclusters. Compared to undoped samples, the cobalt-doped nanoparticle catalysts exhibit a greater specific surface area, increased acidity, enhanced chemisorbed oxygen, and improved redox properties, all contributing to superior denitrification efficacy. Additionally, Density Functional Theory (DFT) calculations provide assertive evidence into the reaction mechanism, showing that Co2+ sites effectively adsorb and activate NH₃, while Co0 sites are crucial for NO adsorption and activation. The synergistic interaction between Co2+ and Co0 facilitates NN coupling, enhancing overall reaction efficiency. These findings underscore the potential of cobalt-modified catalysts for practical industrial applications, offering robust performance over a wide temperature range and meeting stringent environmental regulations.

Alloying effects on the reactivity of Pd are ensemble dominated

In this paper the geometric (“ensemble”) and electronic (“ligand”) effects of alloying on surface reactivity and catalysis are considered. The effect of alloying on the behaviour of Pd, both in single crystal form, and as a nanoparticulate catalyst is discussed. The first case concerns Pd alloyed with Cu, and here the reactivity with formic acid and ethanol is modified by the presence of Cu. However, both Cu and Pd maintain their elemental integrity for the reactions, and it is shown that the main alloying effect is one of dilution of Pd atoms, rather than by global electronic factors such as d-band shifting and filling. Similarly, when Pd is alloyed with Au, then the adsorption characteristics (sticking probability and uptake) for CO, O2, ethene and acetaldehyde are dominated by changes in the surface arrangement of the two atoms. Au mainly acts as an adsorption blocker, but to different degrees depending upon the nature of the adsorbing molecule and its demand for particular ensemble sizes. Finally, nanoparticulate Pd is considered, and the effect of alloying on high pressure methanol synthesis from CO2 and H2 is outlined. Pd on its own is not very selective, instead it mainly produces CO and methane. However, by supporting on oxides such as ZnO, Ga2O3 and In2O3 and by reducing in hydrogen, the Pd forms alloys, which then results in high selectivity to methanol. Again, this is ascribed to the dilution of the Pd ensembles at the surface, which are the cause of methane production.

Precise Size Determination of Supported Catalyst Nanoparticles via Generative AI and Scanning Transmission Electron Microscopy.

Transmission electron microscopy (TEM) plays a crucial role in heterogeneous catalysis for assessing the size distribution of supported metal nanoparticles. Typically, nanoparticle size is quantified by measuring the diameter under the assumption of spherical geometry, a simplification that limits the precision needed for advancing synthesis-structure-performance relationships. Currently, there is a lack of techniques that can reliably extract more meaningful information from atomically resolved TEM images, like nuclearity or geometry. Here, cycle-consistent generative adversarial networks (CycleGANs) are explored to bridge experimental and simulated images, directly linking experimental observations with information from their underlying atomic structure. Using the versatile Pt/CeO2 (Pt particles centered ≈2nm) catalyst synthesized by impregnation, large datasets of experimental scanning transmission electron micrographs and physical image simulations are created to train a CycleGAN. A subsequent size-estimation network is developed to determine the nuclearity of imaged nanoparticles, providing plausible estimates for ≈70% of experimentally observed particles. This automatic approach enables precise size determination of supported nanoparticle-based catalysts overcoming crystal orientation limitations of conventional techniques, promising high accuracy with sufficient training data. Tools like this are envisioned to be of great use in designing and characterizing catalytic materials with improved atomic precision.