High Metal Loading Research Articles

Dry‐Solid‐Electrochemical Synthesis: A General Method for Large Scale Synthesis of Single‐Atom Catalysts with High Metal loadings

AbstractSingle‐atom catalysts (SACs) with high metal loadings are highly desirable but still challenging for large scale synthesis. Here we report a new technique named as dry‐solid‐electrochemical synthesis (DSES) for a general large‐scale synthesis of SACs with high metal loadings in an energy‐conservation and environment‐friendly way. With it, a series of pure carbon‐supported metal SACs (Platinum up to 35.0 wt %, Iridium 21.2 wt %, Ruthenium 20.4 wt % and Iron 17.6 wt %) with high metal loadings were obtained. Particularly, a Pt SAC with Pt 23.9 wt % and remarkable oxygen reduction reaction (ORR) performance in fuel cells is synthesized on kilogram scale. Based on multiple control experiments, a unique redox mechanism for DSES process is proposed: metal precursors on conductive supports are reduced to metals via a homolytic cleavage of metal‐halogen bonds by the attacking of electrons flowing through the dry solid phase. Such versatile technique paves a new economical and environment‐friendly pathway for fabricating high‐metal‐loading SACs or atomic dispersion catalysts.

Dry-Solid-Electrochemical Synthesis: A General Method for Large Scale Synthesis of Single-Atom Catalysts with High Metal loadings.

Single-atom catalysts (SACs) with high metal loadings are highly desirable but still challenging for large scale synthesis. Here we report a new technique named as dry-solid-electrochemical synthesis (DSES) for a general large-scale synthesis of SACs with high metal loadings in an energy-conservation and environment-friendly way. With it, a series of pure carbon-supported metal SACs (Platinum up to 35.0 wt%, Iridium 21.2 wt%, Ruthenium 20.4 wt% and Iron 17.6 wt%) with high metal loadings were obtained. Particularly, a Pt SAC with Pt 23.9 wt% and remarkable oxygen reduction reaction (ORR) performance in fuel cells is synthesized on kilogram scale. Based on multiple control experiments, a unique redox mechanism for DSES process is proposed: metal precursors on conductive supports are reduced to metals via a homolytic cleavage of metal-halogen bonds by the attacking of electrons flowing through the dry solid phase. Such versatile technique paves a new economical and environment-friendly pathway for fabricating high-metal-loading SACs or atomic dispersion catalysts.

Ultrasonic-assistance influence on the impregnation method for high metal loading CoMo/Ti-HMS catalysts

Ultrasonic-assistance influence on the impregnation method for high metal loading CoMo/Ti-HMS catalysts

Reusable ReOx‐Pd/CeO2 Catalyst with Low Metal Surface Concentration for Efficient Consecutive Deoxydehydration and Hydrogenation of Vicinal OH Groups

A strategy is proposed to enhance the stability and reusability of the ReOx‐Pd/CeO2 catalyst for the consecutive deoxydehydration and hydrogenation (DODH + HG) of biomass‐derived vicinal diols. A remarkable result involving a simultaneous enhancement of activity, stability, and regeneration ability of the catalyst is obtained by lowering the surface concentration of metals. Using erythritol as a model compound, DODH + HG over a low‐loading ReOx‐Pd/CeO2 can be completed much faster with a higher turnover number compared to the high‐loading standard catalyst. Moreover, a three‐fold decrease in deactivation rate is also obtained when shifting from a 2 wt% Re‐containing catalyst to a 0.5 wt% one, confirming the enhancement of stability. The regeneration of a low‐loading ReOx‐Pd/CeO2 (0.5 wt% Re) can be completely achieved via heat‐treatment under air in milder conditions at a temperature as low as 353 K. Based on Raman spectroscopy, no sign of polymeric ReOx could be detected on the surface of a spent ReOx‐Pd/CeO2 (0.5 wt% Re) after a simple oven drying under air, confirming the complete redispersion of the inactive species, which was previously traced as the main cause of catalyst deactivation in the catalyst with a higher metal loading.

Enhanced fischer-tropsch synthesis performance on Co@SiO2 catalyst with core-shell structure

Energy is of great importance for the development of modern society, which is mostly dependent on crude oil. Due to the severe pollution caused by using crude oil and the diminishing of crude oil reserves, it is urgent to look for clean oil from alternative resource other than crude oil. Currently, Coal-to-Liquid (CTL) or Biomass-to-Liquid (BTL) technology is an important way to produce clean liquid fuels through Fischer-Tropsch Synthesis (FTS) of syngas. For FTS process, catalyst is a main factor for affecting on syngas conversion and product distribution. For traditional oxides-supported catalysts, the mutual constraint between active metal loading and dispersion at high metal loading is hard to overcome, which will hinder the synthesis of high-performance FTS catalysts. In this paper, a new type of Co@SiO2-T (CS-T) and Co@SiO2-X (CS-X) catalysts with core-shell structure were prepared by using polyvinyl pyrrolidone (PVP) as the structural stabilizer, hexadecyl trimethyl ammonium Bromide (CTAB) as the templating agent and tetraethyl orthosilicate (TEOS) as the silica source. The effects of hydrothermal temperature and pyrolysis temperature on the catalyst physical-chemical properties and FTS performance were investigated. The results showed that increasing the hydrothermal temperature favored the formation of the core-shell structure of the catalysts. With the increase of pyrolysis temperature, the catalyst particle size decreased from 0.54 μm to 0.23 μm. The FTS activities of the catalysts showed a volcano trend with hydrothermal and pyrolysis temperatures.

Salt template-assisted polymer tethering strategy to achieve high dispersed cobalt single atoms/clusters on porous carbon catalysts for effective Fenton-like reactions

The exploration of the synthesis of porous carbon-supported metal nanocatalysts with high metal loading and dispersion for the development of heterogenous catalysts is important. However, this remains a challenging subject. In this paper, a salt template-assisted polymer tethering strategy was proposed to prepare Co single atom and ultrafine cluster anchored on porous carbon (Co-NPC) with a high-loading of 16.9wt%, thereby exposing high density of reaction sites. The obtained Co-NPC catalyst exhibited excellent catalytic performance for almost 100% degradation of bisphenol A (BPA) within 20min, which is much faster than the CoSA-NPC catalyst with only single atom sites and Co-NC without salt template added. Radical quenching experiments and electron paramagnetic resonance tests verified that both the nonradical oxidation pathway by 1O2, the electron transfer and radical oxidation pathway by •OH, SO4•- appeared during the degradation process. After 3 cycles, the removal rate of BPA did not decrease significantly. The fixed bed experiment revealed that Co-NPC could realize the continuous degradation of methylene blue (MB) with almost 100% degradation efficiency. This research indicated that the strategy by pyrolyzing metal coordinated polymer is a potential method for the synthesis of high metal loading catalyst at gram scale, meeting the requirement of practical applications.

Tailoring ORR Activity in Fe-N-C Catalysts through Phosphorus Incorporation.

Atomically dispersed iron and nitrogen co-doped carbon materials (Fe-N-C) represent promising non-precious metal catalysts for the oxygen reduction reaction (ORR), offering potential alternatives to noble metal-based benchmarks. In our study, we investigated the influence of phosphorus doping on the catalytic activity of Fe-N-C. The experimental research demonstrate that the doping of phosphorus significantly enhances the ORR activity. Specifically, the resulting Fe-NPC exhibits high metal loading and excellent ORR activity in 0.1 M KOH with an onset potential of 1.00 V and a half-wave potential of 0.864 V. Density functional theory (DFT) simulations reveal that phosphorus improves the electrocatalytic activity by activating O2 molecules and reducing the energy barrier (the hydrogenation reaction *OH→H2O) of the rate-determining step. Furthermore, Fe-NPC exhibits promising application prospects as an air cathode in Zn-air batteries, delivering a high maximum discharge power density of 180.3 mW cm-2 and outstanding discharge specific capacity (758.8 mAh g-1 Zn) at a discharge current density of 10 mA cm-2.

A novel and facile strategy for the preparation of highly reactive NiMo/γ-Al2O3 hydrodesulfurization catalyst

Traditionally, the commercial Ni(Co)Mo(W)/Al2O3 hydrodesulfurization (HDS) catalysts were prepared with corresponding oxidation precursors and then sulfured with CS2 or H2S, which is complex and time-consuming. Herein, a novel “O-S exchanging” strategy was proposed to directly synthesize a series of highly efficient Ni-MoS2/Al2O3 HDS catalysts with various Mo loading using MoS42− solution as a novel active precursor, and their catalytic performances were evaluated for 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS. The experimental results showed that under the same reaction conditions, the catalyst with 15 wt% MoO3 (S-CAT-15) exhibited a HDS rate up to 99.8 % for 240 h, which was not only nearly two times higher than that of O-CAT-15 counterpart prepared by the conventional oxidation precursor with the same metal loading, but also even 1.6 times higher than that of O-CAT-20 with a higher metal loading, demonstrating its excellent HDS performance and outstanding stability. The deep characterization analyses unveiled that the superior HDS performance of S-CAT-15 was attributed to this novel strategy, which not only notably improved the sulfidation of Mo species, but also considerably promoted the decoration of Ni atoms onto the edges of MoS2 slabs forming more reactive Type-II Ni-Mo-S sites, thereby remarkably enhancing the HDS performances of S-CAT catalysts. This work may offer a novel protocol to guide the fabrication of more efficient industrial hydrogenation catalysts in the future.

Mechanistic Insights into the Formation and Growth of Supported Metal Nanoparticles By an Identical-Location Synthesis Approach

Electrocatalysts are key materials for the development of a wide range of renewable energy technologies, such as fuel cells, electrolyzers, and P2X devices. Often the best catalysts in terms of the activity and stability take the form of well-dispersed precious metal particles supported on a highly durable and conductive substrate. In particular, for high-temperature proton-exchange membrane fuel cells, the anode catalyst most desired by the industry is Pt-based nanoparticles of 4-5 nm with a high metal loading (e.g. 50 wt%) well dispersed on a graphitized carbon support. Unfortunately, synthesis of such catalysts on a sufficiently large scale has rarely been achieved.Recently, our group has developed a solid-state chemical process for the synthesis of supported electrocatalysts.1, 2 Regarding the particle formation mechanism, the classical nucleation theory provides a fundamental basis for understanding the synthesis process, but it is insufficient to predict the detailed mechanism when synthesis precursors of specific structures are involved. Herein, we report our recent progress in understanding the key processes governing the formation and growth of Pt nanoparticles on different carbon supports, through investigations using an identical-location synthesis approach. Figure 1 shows the TEM images of a synthesis precursor before and after the reduction step. Based on the insights gained, we have attempted to synthesize the much-anticipated catalyst, graphitized carbon supported Pt-based nanoparticles. We believe that the mechanistic insights obtained and the syntheses demonstrated will provide important guidance for the synthesis of various types of supported catalysts. Furthermore, we expect this method to be suitable for the synthesis of catalysts on a larger scale.

Baselining Unitized Reversible Fuel Cells with Low Catalyst Loadings: Performance and Durability Insights

Unitized Reversible Fuel Cells (URFCs) combines the functionality of hydrogen fuel cells and water electrolyzers into a single device, offering high energy density for energy conversion and storage. However, their commercial viability is deterred by the high precious group metal (PGM) loadings. Conventional URFCs utilize 1 mg/cm2 of Pt and 1 mg/cm2 of IrO2 in the oxygen electrode, posing economic and sustainability challenges.This study investigates the performance and durability implications of minimizing PGM loadings in oxygen electrode which utilizes a mixture of IrO2 and Pt black to facilitate oxygen evolution and oxygen reduction reaction respectively. We also examine the effect of the porous transport layer (PTL) morphology and wettability on the URFC performance and durability. Accelerated stress test (AST) protocol was developed to evaluate the performance loss across both fuel cell and water electrolyzer mode of URFC operation. Additionally, this research provides a detailed characterization of loss in active area, change in catalyst layer structural, and PTL wettability offering insights into the degradation mechanism in URFCs.This study not only establishes a foundational benchmark for understanding the URFC performance and durability at low catalyst loadings but also highlights the critical need for strategic component selection and activation methods to enhance the system's overall efficiency and durability, marking a significant step towards the realization of more sustainable energy solutions.

High-Loading Intermetallic PtCo Nanoparticles Supported on S-Doped Carbon for Oxygen Reduction Reaction Catalysts

Improving catalysts for the oxygen reduction reaction (ORR) is crucial for commercialization of proton exchange membrane fuel cells (PEMFCs) due to the sluggish kinetics of ORR at the cathode. Current ORR catalysts face challenges such as high costs associated with precious metals and poor durability. A common approach to improve catalyst activity is to alloy Pt with transition metals, such as cobalt and nickel, to control the d-band center. Instead of the disordered PtM, Pt intermetallic compounds show improved ORR intrinsic activity and enhanced stability. Also, doping carbon supports with heteroatoms such as nitrogen and sulfur is a feasible strategy to enhance the interaction between the metal nanoparticles of the catalyst and its support, which leads to improved performance and stability of the catalysts.In this study, we synthesized high-loading intermetallic PtCo nanoparticles supported on sulfur-doped carbon. High metal loading catalysts have significant advantages for practical PEMFC applications as they accelerate mass transport, leading to a reduction in voltage loss, especially under high current densities. To synthesize high-loading intermetallic PtCo nanoparticles, uniform sulfur doping on commercial carbon support is introduced, since sulfur sites can anchor metal nanoparticles even during a harsh heat treatment process. The sulfur sites not only minimize sintering, but also improve the electrochemical performance. Using this approach, high-loading (52.5 wt%) sub-5 nm PtCo intermetallic compounds with a Pt-rich shell (PtCo@Pt/S-BP) were successfully synthesized. The morphology and characteristics of the PtCo nanoparticles were confirmed through various techniques, including XRD, TEM, ICP-OES, HAADF-STEM, EDS mapping, and XPS analysis. In the half-cell test, PtCo@Pt/S-BP exhibited over 5-fold enhancement in mass activity and 6-fold increase in specific activity compared to commercial Pt/C. Additionally, the performance of PtCo@Pt/S-BP was maintained even after 50,000 cycles due to thermodynamically stable structure of the intermetallic phase and Pt-rich shell. This synthesis strategy provides a promising pathway for practical application of Pt-based catalysts in future PEMFCs.

Defect engineering induced high metal loading Co-single-atom catalyst on carbon dots for efficient H2O2 electrosynthesis

Co-single atom catalysts (Co-SACs) exhibit high selectivity and efficiency for H2O2 electrosynthesis via the two-electron oxygen reduction reaction (2e−ORR), with the catalytic activity as significantly influenced by the loading content of Co atoms. However, the loading of Co atoms is typically confined to a low level (<1.0 wt%), which restricts their overall catalytic performance. Herein, we proposed a defect engineering strategy that utilized the carbon dots (CDs) as a platform to capture Co atoms, and constructed a series of Co-SACs with high Co atoms loading (with a maximum of 6.16 wt%), representing a substantial improvement compared to existing benchmarks in the literature. Experimental and characterization results revealed that the defect sites on CDs allowed adequate spacing between the Co atoms, effectively preventing their aggregation and promoting the generation of highly loaded metal atoms. It is worth noting that ECDs-CoSA demonstrated remarkable efficacy and catalytic activity with 93.70 % H2O2 selectivity and an impressive H2O2 yield of 9.71 mol L−1 h−1 gcat.−1 in neutral condition. This study presents an effective route for the controlled prepared of Co-SACs with high metal loading, aiming at sustainable and the efficient H2O2 electrosynthesis.

Scalable Atomic‐Layer Tailoring of Abundant Oxide Supports Unlocks Superior Interfaces for Low‐Metal‐Loading Dehydrogenation

Liquid organic hydrogen carriers (LOHCs) offer a promising solution for global hydrogen infrastructure, but their practical application faces two key challenges: sluggish dehydrogenation processes and the reliance on catalysts with high noble metal loadings. This study presents a scalable approach to reduce noble metal usage while maintaining high catalytic activity. We synthesized an ultralow Pt content (0.1 wt%) catalyst using γ‐Al2O3‐based pellet support with atomic layer deposition (ALD) of TiO2. Advanced characterization techniques reveal that the thin ALD‐TiO2 shell provides a heterogeneous interface, confining electronically rich Pt‐nanoparticle ensembles. The catalyst outperforms both equivalent Pt‐content catalysts and a commercial 0.5 wt% Pt/γ‐Al2O3 catalyst in homocyclic LOHC dehydrogenation. This study provides insights into the beneficial role of ALD‐engineered interfaces for catalytic supports and offers an efficient approach for scalable production of low‐noble‐metal‐content catalysts, with implications for various catalytic processes.

Scalable Atomic-Layer Tailoring of Abundant Oxide Supports Unlocks Superior Interfaces for Low-Metal-Loading Dehydrogenation.

Liquid organic hydrogen carriers (LOHCs) offer a promising solution for global hydrogen infrastructure, but their practical application faces two key challenges: sluggish dehydrogenation processes and the reliance on catalysts with high noble metal loadings. This study presents a scalable approach to reduce noble metal usage while maintaining high catalytic activity. We synthesized an ultralow Pt content (0.1 wt %) catalyst using γ-Al2O3-based pellet support with atomic layer deposition (ALD) of TiO2. Advanced characterization techniques reveal that the thin ALD-TiO2 shell provides a heterogeneous interface, confining electronically rich Pt-nanoparticle ensembles. The catalyst outperforms both equivalent Pt-content catalysts and a commercial 0.5 wt % Pt/γ-Al2O3 catalyst in homocyclic LOHC dehydrogenation. This study provides insights into the beneficial role of ALD-engineered interfaces for catalytic supports and offers an efficient approach for scalable production of low-noble-metal-content catalysts, with implications for various catalytic processes.

Flower-like boron-doped zinc single-atom nanozymes for colorimetric sensing and smartphone-assisted detection of Cr(VI)

With the development of electronics, electroplating, printing, and dyeing industries, environmental pollution caused by hexavalent chromium (Cr(VI)) has become increasingly prominent. Skin contact with Cr (VI) can cause allergies or genetic defects, and inhalation can cause cancer, which is a lasting danger to the environment and the human body. Developing effective strategies to monitor Cr(VI) in environmental water or industrial wastewater can evaluate the degree of water pollution and risk warning, thus helping to prevent the spread of Cr(VI) pollution, promote the protection of water resources and the ecological environment, and ensure human safety and sustainable development. On the basis of the regulation of dopamine, boron-doped zinc single-atom nanozymes (Zn/B-NC SAzymes) with three-dimensional nanoflower morphology were controlled in this work. The introduction of B in Zn/B-NC SAzymes and the high metal loading of Zn (6.5 wt%) led to the formation of more active sites, resulting in the material showing excellent enzyme-like activity. H2O2 decomposed to generate superoxide radicals under the catalysis of Zn/B-NC SAzymes, which then oxidized the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to generate blue oxTMB. When Cr(VI) was introduced into the sensor system, the color of blue oxTMB is deepened, and the colorimetric method of Cr(VI) was constructed. The linear range is 0.2–40 μM, LOD is 59 nM, and the visual detection of Cr (VI) is performed with the aid of the smartphone. This work not only provides experimental and theoretical guidance for understanding the active centers of Zn-SAzymes and their catalytic processes, but also provides a promising and alternative detection strategy for the rapid and even visual on-site detection of Cr(VI) in aquatic environments, which is of great significance for the control of Cr(VI) pollution in the environment and industrial wastewater.

Ligand-Coordinated Pt Single-Atom catalyst facilitates Support-Assisted Water-Gas shift reaction

The water–gas shift (WGS) reaction (CO+H2O→CO2+H2,ΔH=-41.1kJ/mol) is an essential process in the production of hydrogen and has grown significantly in usage over time. In this study, we further explore a novel strategy that can create single-atom catalysts (SACs) from metal-ligand single-sites on high surface area oxide supports for catalyzing the WGS reaction. The metal–ligand approach results in high metal loading, exhibits an ultimate dispersion of metal species and maximizes atom efficiency. 1,10-phenanthroline-5,6-dione (PDO) was chosen as the ligand for its oxidative potential for stabilizing Pt metal cations via two different binding pockets. The single-atom nature of the Pt-ligand is characterized with extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and transmission electron microscopy (TEM) techniques. The catalytic activity is evaluated for the WGS reaction, revealing that Pt-ligand SACs supported on defective TiO2 show higher inherent catalytic activity than Pt NPs and a significantly lower activation energy. This characteristic is generally desirable for the redox mechanism. Density functional theory (DFT) calculations reveal that metal–ligand SACs allow CO interaction with oxygen atoms from the TiO2 surface. The redox mechanism of the WGS reaction demonstrates a lower effective activation barrier than the associative mechanism for Pt-ligand SAC. Moreover, the metal–ligand strategy, according to DFT results, facilitates the reaction redox mechanism by reducing the CO binding energy and promoting CO2 and H2 formation process.

Ammonia-regulated dynamic evolution of Ti precursor incorporating into dealuminized beta for efficient 1-Hexene epoxidation

Demetalation-metalation method has gained prominence for its higher metal loading, efficiency and shortened synthetic period, particularly in the incorporation of metal atoms with large radii into zeolite framework in recent years. An ammonia-regulated approach has been developed for selectively evolved deep-substituted Ti precursors in dealuminized beta zeolites, which enables a controlled promotion of metalation of Ti atoms. Additionally, this ammonia-regulated approach could also enhance 1-hexene kinetic adsorption by constructing mesopores, which is demonstrated by the lower reaction order of 1-hexene. The synthesized ammonia-regulated N-Ti-beta exhibits rich framework Ti species and a high specific surface area, leading to significantly improved 1-hexene epoxidation performance (conversion of 61%, selectivity of 98%, and a high H2O2 utilization efficiency of 93%). This study not only provides a new strategy to dynamically regulate evolution of Ti precursors by ammonia but also holds promise for advancing related industrial processes in demetalation-metalation methods.

Oceanic anoxic event 3 in Arctic Canada—Arc volcanism and ocean fertilization drove anoxia

The global extent of the Late Cretaceous oceanic anoxic event 3 (OAE 3) remains uncertain. It is not considered to have extended into the Boreal Realm. To test this, we examined Late Cretaceous organic- and metal-rich black mudstones of the Smoking Hills Formation in Arctic Canada. New high-precision U-Pb zircon ages indicate that deposition of the Smoking Hills Formation (88.535−78.230 Ma) was temporally coincident with OAE 3, indicating a much broader global expression of this event than previously thought. OAE 3 was likely manifest throughout the proto−Arctic Ocean (now Arctic Canada). Abundant bentonite layers and cryptotephra within the Smoking Hills Formation have rare earth element (REE) patterns that are consistent with ashfall derived from Cretaceous arc volcanism. Anomalously high organic matter content in the Smoking Hills Formation, as compared to underlying and overlying units, suggests that ocean fertilization led to enhanced productivity and metal drawdown. A peak in arc volcanism may have been a key driver of the OAE 3 event. We also explored the potential use of cadmium as a geochemical marker of volcanism and show that high volcanogenic metal loading could affect the use of Cd and other proxies for marine productivity (e.g., Zn, Cu).

Carboxylated albumin as a dual-purpose template for fabricating gadolinium oxide nanoprobe with high metal loading and exceptional relaxivity

Biomineralization is a highly efficient approach to synthesizing magnetic resonance imaging (MRI) probes but encounters two limitations: low metal loading and insufficient sensitivity. Herein, based on the Solomon-Bloembergen-Morgan theory and hard and soft acids and bases principle, we proposed the use of fully carboxylated albumin as a dual-purpose template for fabricating gadolinium oxide (BSA-COOH-Gd2O3) nanoprobe with high metal loading and exceptional relaxivity for the first time. The proposed nanoprobe was synthesized using a straightforward one-pot method under mild conditions, exhibiting excellent biocompatibility, good water solubility, high Gd content (6 %), and outstanding relaxivity (41.17 mM-1s−1). In vivo magnetic resonance angiography (MRA) demonstrated that the BSA-COOH-Gd2O3 nanoprobe (0.05 mmol Gd/kg, equivalent to half of the clinical dose) exhibited a sustained and significantly enhanced vascular enhancement effect for at least 2 h with exceptional resolution, enabling clear visualization of vessels as small as 0.3 mm at 3.0 T and 0.13 mm at 9.4 T. Both the severity and location of vascular narrowing can be accurately identified in a carotid artery stenosis model and the tumor can be sensitively detected in a tumor model via the nanoprobe-based MRI. Our study provides an upgraded biomineralization technique for synthesizing high-performance MRI nanoprobes for various applications.

Rational design of precious tetrametallic single-cluster catalysts for electrocatalytic nitrate reduction reaction

Single cluster catalysts (SCCs) with high metal loading can exhibit extraordinary catalytic activity in electrocatalytic reactions, but the rational design of active sites remains a challenge. Herein, we proposed a series of SCCs with pyramid-shaped precious tetrametallic clusters anchored on g-CN monolayer (M4/g-CN) as efficient catalysts for the electrochemical reduction of nitrate to ammonia (NO3RR). By means of first-principle computations, the stability, catalytic mechanism and activity, as well as selectivity of these SCCs are systematically investigated. The calculation results show that most SCCs (Ru4/g-CN, Rh4/g-CN, Pd4/g-CN, Os4/g-CN, Ir4/g-CN, Pt4/g-CN) are thermodynamically stable due to the strong binding energy and significant charge transfer behavior between tetrametallic clusters and g-CN support. More important, the volcano curve between limiting potentials and adsorption free energy of NO3‾ can be established, in which Ir4/g-CN can exhibit optimal NO3RR activity due to its location of volcano top. Further analysis of electronic structures reveals that the special pyramid configuration can significantly promote the enrichment of charge on active site and elevate its d-band center, and thus facilitates the NO3RR. This finding pours new vigor into the development of the SCCs family.