Advanced Catalysts Research Articles

Suppressing surface segregation by introducing lanthanides to enhance high-temperature oxygen evolution reaction activity and durability

Abstract Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a conventional anode material for solid oxide electrolysis cells (SOECs) to catalyze oxygen evolution reactions (OERs). However, the inferior chemical stability of BSCF results in severe surface segregation and performance degradation under high temperatures. A critical challenge lies in alleviating surface segregation and preserving the high OER performance of BSCF anodes. Herein, lanthanides are introduced to substitute the Ba in BSCF, labeled as Ln0.5Sr0.5Co0.8Fe0.2O3−δ (LnSCF, Ln = La, Pr, Nd, Sm), to regulate its stability and performance. The introduction of La and Pr effectively enhances stability, suppresses surface segregation and maintains high OER activity. Continuous lattice oxygen loss and Co ion oxidation of LnSCF are demonstrated upon annealing in oxidizing atmosphere; thus, we propose that surface segregation is a self-regulation mechanism of perovskite lattice to tolerant oxidizing atmosphere. Perovskite oxides maintain structurally stable via decreasing A-site valence state and forming surface segregation. SOECs with La0.5Sr0.5Co0.8Fe0.2O3−δ anodes deliver an optimal current density of 1.69 A cm−2 at 1.6 V and stability for CO2 electrolysis at 800 °C, shedding light on designing advanced catalysts for high-temperature OER.

Iron‐Nitrogen‐Carbon Aerogel for Enhanced Oxygen Reduction in Acidic Media: The Influence of Temperature

AbstractThe oxygen reduction reaction (ORR) in an acidic environment is crucial for fuel cell technology. Understanding its complex kinetics and developing advanced catalyst materials have the potential to drive significant improvements in energy efficiency, paving the way for sustainable, green energy solutions. In this work, Iron‐Nitrogen‐Carbon@aerogel (Fe(FcP)x‐N‐C@Aerogel) catalysts are developed by carbonizing polypyrrole (PPy) and ferrocene. The ORR performance of these catalysts is investigated across different annealing temperatures. The catalysts’ shape and structure are validated through scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS), revealing that changes in annealing temperature affect morphology and nitrogen‐containing functional groups of the catalyst. Linear sweep voltammetry (LSV) and rotating disk electrode (RDE) studies demonstrated that Fe(FcP)800‐N‐C@Aerogel catalysts exhibit excellent performance, with a half‐wave potential of 0.687 V and an average electron transfer number of 3.98 under acidic conditions. These findings suggest a near‐four‐electron reaction pathway, highlighting the catalyst's strong ORR activity, high efficiency, and durability, with only 17.4 mV LSV curve decay after 10,000 cycles. In conclusion, Fe(FcP)x‐N‐C@Aerogel advances ORR catalysis in acidic media by delivering exceptional performance and durability, driven by its innovative architecture and precisely engineered active sites, setting a new benchmark for high‐efficiency energy conversion.

Identifying the Bifunctional Mechanism in Alkaline Water Electrolysis by Lewis Pairs at the Single-Atom Scale.

The bifunctional mechanism, involving multiactive compositions to simultaneously dissociate water molecules and optimize intermediate adsorption, has been widely used in the design of catalysts to boost water electrolysis for sustainable hydrogen energy production but remains debatable due to difficulties in accurately identifying the reaction process. Here, we proposed the concept of well-defined Lewis pairs in single-atom catalysts, with a unique acid-base nature, to comprehensively understand the exact role of multiactive compositions in an alkaline hydrogen evolution reaction. By facilely adjusting active moieties, the induced synergistic effect between Lewis pairs (M-P/S/Cr pairs, M = Ru, Ir, Pt) can significantly facilitate the cleavage of the H-OH bond and accelerate the removal of intermediates, thereby switching the rate-determining step from the Volmer step to the Heyrovsky step. Moreover, the representative Ru-P Lewis pairs deliver an impressive 266 h durability at a high industrial current density of 2 A cm-2 without activity decay in anion-exchange membrane water electrolysis, and the concept can be extended to modify commercial noble-metal-based catalysts for performance enhancement. This work not only sheds light on the important effect of the bifunctional mechanism in alkaline water electrolysis at the single-atom scale but also offers a universal descriptor for the rational design of advanced catalysts.

Efficient amine-assisted CO2 hydrogenation to methanol co-catalyzed by metallic and oxidized sites within ruthenium clusters

Amine-assisted two-step CO2 hydrogenation is an efficient route for methanol production. To maximize the overall catalytic performance, both the N-formylation of amine with CO2 (i.e., first step) and the subsequent amide hydrogenation (i.e., second step) are required to be optimized. Herein, a class of Al2O3-supported Ru catalysts, featuring multiple activated Ru species (i.e., metallic and oxidized Ru), are rationally fabricated. Density functional theory calculations suggest that metallic Ru forms are preferred for N-formylation step, whereas oxidized Ru species demonstrate enhanced amide hydrogenation activity. Thus, the optimal catalyst, containing unique Ru clusters with coexisting metallic and oxidized Ru species, efficiently synergize the conversion of CO2 into methanol with exceptional selectivity (>95%) in a one-pot two-step process. This work not only presents an advanced catalyst for CO2-based methanol production but also highlights the strategic design of catalysts with multiple active species for optimizing the catalytic performances of multistep reactions in the future.

Local Symmetry-Broken Single Pd Atoms Induced by Doping Ag Sites for Selective Electrocatalytic Semihydrogenation of Alkynes.

Engineering the local coordination environment of single metal atoms is an effective strategy to improve their catalytic activity, selectivity, and stability. In this study, we develop an asymmetric Pd-Ag diatomic site on the surface of g-C3N4 for the selective electrocatalytic semihydrogenation of alkynes. The single Pd atom catalyst, which has a locally symmetric Pd coordination, was inactive for the semihydrogenation of phenylacetylene in a 1 M KOH and 1,4-dioxane solution at an applied potential of -1.3 V (vs RHE). In sharp contrast, doping Ag sites into single Pd atom catalyst to form paired Pd-Ag diatomic sites with asymmetric Pd coordination substantially enhanced the reaction, resulting in a high conversion (>98%) with exceptional time-independent selectivity to styrene under identical conditions. Characterization and theoretical calculations reveal that the introduction of a Ag site into single Pd atoms disrupts their symmetry coordination by forming Pd-Ag bonds with N2-Pd-Ag-N configuration, thereby modulating the electronic and geometric structures of Pd sites, which in turn benefits the adsorption and activation of substrate and lowers energy barrier for the rate-determining step of semihydrogenation, ultimately enhancing the electrocatalytic reaction. This work provides a facile and powerful strategy for the design of advanced catalysts by tuning the local coordination environment for selective catalysis.

Enhanced Cooperative Generalized Compressive Strain and Electronic Structure Engineering in W-Ni3N for Efficient Hydrazine Oxidation Facilitating H2 Production.

As promising bifunctional electrocatalysts, transition metal nitrides are expected to achieve an efficient hydrazine oxidation reaction (HzOR) by fine-tuning electronic structure via strain engineering, thereby facilitating hydrogen production. However, understanding the correlation between strain-induced atomic microenvironments and reactivity remains challenging. Herein, a generalized compressive strained W-Ni3N catalyst is developed to create a surface with enriched electronic states that optimize intermediate binding and activate both water and N2H4. Multi-dimensional characterizations reveal a nearly linear correlation between the hydrogen evolution reaction (HER) activity and the d-band center of W-Ni3N under strain state. Theoretically, compressive strain enhances the electron transfer capability at the surface, increasing donation into antibonding orbitals of adsorbed species, which accelerates the HER and HzOR. Leveraging both compressive strain and the modified electronic structure from W incorporation, the W-Ni3N catalysts demonstrate outstanding bifunctional performance, achieving overpotentials of 46mV for HER at 10mA cm-2 and 81mV for HzOR at 100mA cm-2. Furthermore, W-Ni3N catalyst achieves efficient overall hydrazine splitting at a low cell voltage of 0.185V for 50mA cm-2, maintaining stability for ≈450 h. This work provides new insights into the dual engineering of strain and electronic structure in the design of advanced catalysts.

Alloying effect modulated electronic structure of Mo-doped PdIn bimetallene nanoribbons for ambient electrosynthesis of urea.

Designing advanced catalysts for electrosynthesis of urea is of significance yet remains challenging. Herein, ultrathin two-dimensional Mo-doped PdIn bimetallene nanoribbons were synthesized via a one-pot method. Material characterization and electrochemical study revealed that the alloying effect enabled electron transfer from In to Pd and provided dual metal sites with regulated electronic structure for the adsorption and activation of NO3- and CO2, thus facilitating the generation of key active intermediates and promoting the C-N coupling reaction.

Hydrothermally Synthesized NiO-SnO2 Nanocomposite as an Efficient Electrocatalyst for Oxygen Evolution Reaction (OER) and Urea Oxidation Reaction (UOR)

This study presents the synthesis and electrochemical evaluation of a NiO-SnO2 nanocomposite as an advanced catalyst for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in an alkaline medium. The NiO-SnO2 composite, prepared via hydrothermal synthesis and subsequent annealing at different temperatures (400°C, 500°C, 600°C), demonstrated excellent catalytic performance, and attributed to its unique dual-phase structure comprising monoclinic NiO and tetragonal SnO2. XRD, SEM, and XPS analyses confirmed the material's crystallinity, morphology, and chemical states, highlighting the role of annealing temperature in optimizing structural properties. Electrochemical measurements revealed that the composite annealed at 600°C exhibited superior OER and UOR activities, with overpotentials of 320mV and 140mV, respectively, at a current density of 10mAcm⁻². This enhanced performance is attributed to the synergistic effects between NiO and SnO2, which improve electron transport, active site availability, and catalyst stability. The study underscores the potential of NiO-SnO2 composites for energy-efficient water splitting and urea-rich wastewater treatment.

Sulfurization of transition metal inorganic electrocatalysts in Li-S batteries.

Lithium-sulfur (Li-S) batteries have garnered significant attention for their exceptional energy density, positioning them as a promising solution for next-generation energy storage. A critical factor in their performance is the use of transition metal inorganic compound electrocatalysts, prized for their distinctive catalytic properties. Recently, increasing interest has focused on the sulfurization of these catalysts in polysulfide-rich environments, a process that holds great potential for enhancing their efficiency. This review analyzes the sulfurization reactions of various transition metal compounds in Li-S batteries and their profound impact on electrochemical performance. By elucidating the sulfurization process with the assistance of advanced characterization techniques, we aim to reveal the true active sites and intrinsic catalytic pathways of sulfur redox electrocatalysts, offering new insights into the design of advanced catalysts for more efficient lithium polysulfide conversion. These findings are expected to accelerate the development of high-performance Li-S battery technologies.

Synergic effect of a MoS2–V2O5 heterostructure as an advanced catalyst for photocatalytic degradation of methylene blue

The MoS2–V2O5 hetero-structure exhibits superior photocatalytic activity for the degradation of methylene blue due to the synergy as well as strong electronic interaction between MoS2 and V2O5 structures.

MoSSe-graphene hybrid material as an advanced catalyst for hydrogen evolution reaction in water splitting

Abstract Hydrogen, with its high energy density and environmentally friendly nature, holds great promise as a future energy. The development of efficient catalysts for the hydrogen evolution reaction (HER) in water splitting is necessary. In this study, we focused on synthesizing a hybrid material MoSSe-Graphene (MoSSe-Gr) as a catalyst for HER. The MoSSe-Gr hybrid catalyst was synthesized through a solvothermal method followed by calcination under an inert atmosphere at 800 °C. Morphology and structural analysis of the catalyst was analyzed using SEM, TEM, XRD and Raman spectroscopy. The MoSSe-Gr hybrid catalyst exhibited remarkable catalytic activity for HER, showing significantly lower overpotentials of 90 mV and 200 mV at current densities of 1 and 10 mA cm−2, respectively, comparable to the benchmark Pt/C catalyst. Furthermore, the MoSSe-Gr catalyst demonstrated long-term electrochemical stability during HER over a 24 h period in an acidic medium. Furthermore, the MoSSe-Gr catalyst demonstrated long-term electrochemical stability during HER in 24 h duration in an acidic medium. The MoSSe-Gr hybrid catalyst shows great potential as an efficient and stable catalyst for HER, promoting sustainable hydrogen production.

Size‐adjustable High‐Entropy Alloy Nanoparticles as an Efficient Platform for Electrocatalysis

The high entropy alloy (HEA) possesses distinctive thermal stability and electronic characteristics, which exhibits substantial potential for diverse applications in electrocatalytic reactions. However, accurately controlling the size of HEA still remains a challenge, especially for the ultrasmall HEA nanoparticles. Herein, we firstly calculate and illustrate the size impact on the electronic structure of HEA and the adsorption energies of crucial intermediates in typical electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), CO2 electroreduction (CO2RR) and NO3– electroreduction (NO3RR). Under the guidance of theoretical calculations, we synthesize a range of ultrasmall PtRuPdCoNi HEA nanoparticles with adjustable sizes (1.7, 2.3, 3.0, and 3.9 nm) using a one‐step spatially confined approach. Specifically, HEA nanoparticles with 1.7 nm size (HEA‐1.7) endows a 16 mV overpotential at current density of 10 mA cm−2, yielding a mass activity of 31.9 A mgNM‐1 of noble metal in HER, significantly outperforming commercial Pt/C catalyst. This strategy can also be easily applicable to other reduction reactions attributed to the richness of metal components and size adjustability, presenting a promising platform for various electrocatalytic applications as advanced catalysts.

Methanation of carbon dioxide over zirconium-tin oxide-based catalyst

An advanced catalyst, Ni/ZrSn[Formula: see text]Ce[Formula: see text]O4/[Formula: see text]-Al2O3, was synthesized for the methanation of CO2 under moderate conditions of atmospheric pressure and low H2 concentration (4 vol%). The use of scrutinyite-type ZrSn[Formula: see text]Ce[Formula: see text]O4 improved the catalytic activity, likely because of abundant oxygen vacancies for CO2 adsorption and good redox properties for cleavage of the C-O bond of adsorbed CO2. The CH4 yield of 18 wt.% Ni/20 wt.% ZrSn[Formula: see text]Ce[Formula: see text]O4/[Formula: see text]-Al2O3 reached 61.0% with high CO2 conversion (58.4%) at [Formula: see text]C using 1 vol% CO2-4vol% H2-95 vol% Ar at atmospheric pressure.

Size-Adjustable High-Entropy Alloy Nanoparticles as an Efficient Platform for Electrocatalysis.

The high entropy alloy (HEA) possesses distinctive thermal stability and electronic characteristics, which exhibits substantial potential for diverse applications in electrocatalytic reactions. The nanosize of HEA also has a significant impact on its catalytic performance. However, accurately controlling nanosize and synthesizing small HEA nanomaterials remains a challenge, especially for the ultrasmall HEA nanoparticles. Herein, we firstly calculate and illustrate the impact of size on the electronic structure of HEA as well as the adsorption energies of crucial intermediates involved in typical electrocatalytic processes, such as the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), CO2 electroreduction (CO2RR) and NO3 - electroreduction (NO3RR). Under the guidance of theoretical calculations, we synthesize a range of ultrasmall PtRuPdCoNi HEA nanoparticles with adjustable sizes (1.7, 2.3, 3.0, and 3.9 nm) using a one-step spatially confined approach, without any further treatment. Experimentally, the smaller size of HEAs is more favorable for the HER and ORR performances, aligning well with theoretical predictions. Specifically, HEA nanoparticles sized at 1.7 nm (HEA-1.7) endows a 16 mV overpotential at current density of 10 mA cm-2, yielding a mass activity of 31.9 A mgNM -1 of noble metal in HER, significantly outperforming commercial Pt/C catalyst. This strategy can also be easily applicable to other reduction reactions (e.g. CO2, NO3 -) attributed to the richness of metal components and size adjustability, presenting a promising platform for various electrocatalytic applications as advanced catalysts.

Toward synergetic reduction of pollutant and greenhouse gas emissions from vehicles: a catalysis perspective.

It is a great challenge for vehicles to satisfy the increasingly stringent emission regulations for pollutants and greenhouse gases. Throughout the history of the development of vehicle emission control technology, catalysts have always been in the core position of vehicle aftertreatment. Aiming to address the significant demand for synergistic control of pollutants and greenhouse gases from vehicles, this review provides a panoramic view of emission control technologies and key aftertreatment catalysts for vehicles using fossil fuels (gasoline, diesel, and natural gas) and carbon-neutral fuels (hydrogen, ammonia, and green alcohols). Special attention will be given to the research advancements in catalysts, including three-way catalysts (TWCs), NOx selective catalytic reduction (SCR) catalysts, NOx storage-reduction (NSR) catalysts, diesel oxidation catalysts (DOCs), soot oxidation catalysts, ammonia slip catalysts (ASCs), methane oxidation catalysts (MOCs), N2O abatement catalysts (DeN2O), passive NOx adsorbers (PNAs), and cold start catalysts (CSCs). The main challenges for industrial applications of these catalysts, such as insufficient low-temperature activity, product selectivity, hydrothermal stability, and poisoning resistance, will be examined. In addition, the future development of synergistic control of vehicle pollutants and greenhouse gases will be discussed from a catalysis perspective.

Manipulating Trimetal Catalytic Activities for Efficient Urea Electrooxidation-Coupled Hydrogen Production at Ampere-Level Current Densities.

Replacing the oxygen evolution reaction (OER) with the urea oxidation reaction (UOR) in conjunction with the hydrogen evolution reaction (HER) offers a feasible and environmentally friendly approach for handling urea-rich wastewater and generating energy-saving hydrogen. However, the deactivation and detachment of active sites in powder electrocatalysts reported hitherto present significant challenges to achieving high efficiency and sustainability in energy-saving hydrogen production. Herein, a self-supported bimetallic nickel manganese metal-organic framework (NiMn-MOF) nanosheet and its derived heterostructure composed of NiMn-MOF decorated with ultrafine Pt nanocrystals (PtNC/NiMn-MOF) are rationally designed. By leveraging the synergistic effect of Mn and Ni, along with the strong electronic interaction between NiMn-MOF and PtNC at the interface, the optimized catalysts (NiMn-MOF and PtNC/NiMn-MOF) exhibit substantially reduced potentials of 1.459 and -0.129 V to reach 1000 mA cm-2 during the UOR and HER. Theoretical calculations confirm that Mn-doping and the heterointerface between NiMn-MOF and Pt nanocrystals regulate the d-band center of the catalyst, which in turn enhances electron transfer and facilitates charge redistribution. This manipulation optimizes the adsorption/desorption energies of the reactants and intermediates in both the HER and UOR, thereby significantly reducing the energy barrier of the rate-determining step (RDS) and enhancing the electrocatalytic performance. Furthermore, the urea degradation rates of PtNC/NiMn-MOF (96.1%) and NiMn-MOF (90.3%) are significantly higher than those of Ni-MOF and the most reported advanced catalysts. This work provides valuable insights for designing catalysts applicable to urea-rich wastewater treatment and energy-saving hydrogen production.

Interplay Between Metal and Acid Sites Tunes the Catalytic Selectivity Over Pd/Nanodiamond Catalysts.

Metal and acid sites are two of the most crucial catalytically active components in heterogeneous catalysis. While variations in the size, morphology, and heterogeneity of metal species, or the manipulation of the strength, location, and density of acid sites, could significantly impact the catalytic performance, the combination and interplay between these sites are even more critical and have been a recent research focus. To achieve highly efficient and selective synergistic catalysis, it is desired to design a catalyst capable of orchestrating the sequential transformation of all reactants and intermediates at different active sites. In this study, we demonstrate that both acid and metal (Pd) sites can be introduced onto a nanodiamond@graphene (NDG) support particle through simple air oxidation and metal salt deposition-precipitation methods, respectively. The presence and assembly of these two catalytically active sites significantly alter the reaction network for the cyclohexanol conversion reaction. Under this strategy, the selectivity toward designated products─cyclohexene, phenol, and benzene─can be precisely tuned by the presence and patterning of these two sites on the nanodiamond particles. Specifically, we show that the catalyst with both acid sites and Pd ensemble sites, i.e., Pd/NDG, can efficiently convert cyclohexanol through consecutive dehydration and dehydrogenation reactions to form benzene with high selectivity (>80%). These findings underscore the potential of integrating metal and acid sites to design advanced catalysts with tailored reactivity and selectivity, paving the way for more efficient and versatile catalytic processes in industrial applications.

Integrating Interactive Ir Atoms into Titanium Oxide Lattice for Proton Exchange Membrane Electrolysis.

Iridium (Ir)-based oxide is the state-of-the-art electrocatalyst for acidic water oxidation, yet it is restricted to a few Ir-O octahedral packing modes with limited structural flexibility. Herein, the geometric structure diversification of Ir is achieved by integrating spatially correlated Ir atoms into the surface lattice of TiO2 and its booting effect on oxygen evolution reaction (OER) is investigated. Notably, the resultant i-Ir/TiO2 catalyst exhibits much higher electrocatalytic activity, with an overpotential of 240 mV at 10 mA cm-2 and excellent stability of 315 h at 100 mA cm-2 in acidic electrolyte. Both experimental and theoretical findings reveal that flexible Ir─O─Ir coordination with varied geometric structure plays a crucial role in enhancing OER activity, which optimize the intermediate adsorption by adjusting the d-band center of active Ir sites. Operando characterizations demonstrate that the interactive Ir─O─Ir units can suppress over-oxidation of Ir, effectively widening the stable region of Ir species during the catalytic process. The proton exchange membrane (PEM) electrolyzer, equipped with i-Ir/TiO2 as an anode, gives a low driving voltage of 1.63 V at 2 A cm-2 and maintains stable performance for over 440 h. This work presents a general strategy to eliminate the inherent geometric limitations of IrOx species, thereby inspiring further development of advanced catalyst designs.

Advancements in catalysts, process intensification, and feedstock utilization for sustainable biodiesel production

Advancements in catalysts, process intensification, and feedstock utilization for sustainable biodiesel production

Ordered Pt3Ni intermetallic compound: A high-performance oxygen reduction reaction catalyst for Zn-air batteries

The development of advanced catalysts for oxygen reduction reaction (ORR) is crucial for Zinc-air batteries (ZABs). In this study, we focus on the controlled synthesis of ordered Pt3Ni intermetallic compounds through impregnation and high-temperature annealing, aiming to enhance the ORR performance for ZABs. The ordered Pt3Ni (denoted as Pt3Ni) and conventional alloy Pt3Ni (denoted as A-Pt3Ni) are synthesized at 600 ℃ and 200 ℃, respectively. Detailed structural characterizations confirm the formation of both ordered and disordered structures. Pt3Ni demonstrates superior ORR catalytic activity and stability compared to A-Pt3Ni and commercial Pt/C catalyst, as evidenced by higher half-wave potentials, lower Tafel slopes, and enhanced electrochemical stability. Furthermore, Pt3Ni exhibits exceptional performance in ZABs, with higher power density, specific capacity, and longer cycle life than its counterparts. These findings highlight the potential of ordered Pt3Ni intermetallic compounds as efficient ORR catalysts in ZABs, offering a promising route for the development of advanced energy conversion and storage systems.