Catalytic Active Sites Research Articles

Proton‐Conducting, Vacancy‐Rich HxIrOy Nanosheets for the Fabrication of Low‐Ionomer‐Dependent Anode Catalyst Layer in PEM Water Electrolyzer

The anode catalyst layer is composed of catalytically functional IrOx and protonic conducting ionomer, and largely dictates catalytic performance of proton exchange membrane water electrolyzer (PEMWE). Here, we report a new type of anode nanocatalysts that possesses both IrOx’s catalytic function and high proton conductivity that traditional anode catalysts lack, and demonstrate its ability to construct high‐performance, low‐ionomer‐dependent anode catalyst layer, the interior of which—about 85% of total catalyst layer—is free of ionomers. The proton‐conducting anode nanocatalyst is prepared via protonation of layered iridate K0.5(Na0.2Ir0.8)O2 and then exfoliation to produce cation vacancies‐rich, 1 nm‐thick iridium oxide nanosheets (labeled as □‐HxIrOy). Besides being a proton conductor, the □‐HxIrOy is found to have abundant catalytic active sites for the oxygen evolution reaction due to the optimization of both edge and in‐plane iridium sites by multiple cation vacancies. The dual functionality of □‐HxIrOy allows the fabrication of low‐iridium‐loading, low‐ionomer‐dependent anode catalyst layer with enhanced exposure of catalytic sites and reduced electronic contact resistance, in contrast to common fully mixed catalyst/ionomer layer in PEMWE. This work represents an example of realizing the structural innovation in anode catalyst layer through the bifunctionality of anode catalyst.

Proton-Conducting, Vacancy-Rich HxIrOy Nanosheets for the Fabrication of Low-Ionomer-Dependent Anode Catalyst Layer in PEM Water Electrolyzer.

The anode catalyst layer is composed of catalytically functional IrOx and protonic conducting ionomer, and largely dictates catalytic performance of proton exchange membrane water electrolyzer (PEMWE). Here, we report a new type of anode nanocatalysts that possesses both IrOx's catalytic function and high proton conductivity that traditional anode catalysts lack, and demonstrate its ability to construct high-performance, low-ionomer-dependent anode catalyst layer, the interior of which-about 85% of total catalyst layer-is free of ionomers. The proton-conducting anode nanocatalyst is prepared via protonation of layered iridate K0.5(Na0.2Ir0.8)O2 and then exfoliation to produce cation vacancies-rich, 1 nm-thick iridium oxide nanosheets (labeled as □-HxIrOy). Besides being a proton conductor, the □-HxIrOy is found to have abundant catalytic active sites for the oxygen evolution reaction due to the optimization of both edge and in-plane iridium sites by multiple cation vacancies. The dual functionality of □-HxIrOy allows the fabrication of low-iridium-loading, low-ionomer-dependent anode catalyst layer with enhanced exposure of catalytic sites and reduced electronic contact resistance, in contrast to common fully mixed catalyst/ionomer layer in PEMWE. This work represents an example of realizing the structural innovation in anode catalyst layer through the bifunctionality of anode catalyst.

Isolated and Paired Metal Sites in Zeolites using Solid-State Ion Exchange.

Isolated and paired extraframework transition metal cations in zeolites are emerging as top candidates for numerous applications not limited to selective methane oxidation to methanol, selective catalytic reduction of nitrogen oxides, propane dehydrogenation, propylene epoxidation, and direct air capture of carbon dioxide. Importantly, these well-defined heterogeneous catalysts offer parallels with molecular and metalloenzyme catalytic active sites. Aqueous-phase ion exchange (APIE) is the most common synthesis technique to obtain these catalysts. Solid-state ion exchange (SSIE) is an often-overlooked technique that offers synthetic advantages compared to APIE. Thus, recent advances in solid-state synthesis strategies merit contemporary contextualization. In this minireview we describe the basic principles, methods, mechanisms, challenges, and advances insolid-state ion exchange in the context ofwell-defined transition metal cationactive sites located in extraframework positions of the zeolite.

Isolated and Paired Metal Sites in Zeolites using Solid‐State Ion Exchange

Isolated and paired extraframework transition metal cations in zeolites are emerging as top candidates for numerous applications not limited to selective methane oxidation to methanol, selective catalytic reduction of nitrogen oxides, propane dehydrogenation, propylene epoxidation, and direct air capture of carbon dioxide. Importantly, these well‐defined heterogeneous catalysts offer parallels with molecular and metalloenzyme catalytic active sites. Aqueous‐phase ion exchange (APIE) is the most common synthesis technique to obtain these catalysts. Solid‐state ion exchange (SSIE) is an often‐overlooked technique that offers synthetic advantages compared to APIE. Thus, recent advances in solid‐state synthesis strategies merit contemporary contextualization. In this minireview we describe the basic principles, methods, mechanisms, challenges, and advances in solid‐state ion exchange in the context of well‐defined transition metal cation active sites located in extraframework positions of the zeolite.

Spatial Confinement of Pd Nanoclusters in Pyrene-Based Covalent Organic Frameworks for Boosting Photocatalytic CO2 Reduction.

Photocatalytic CO2 reduction offers a promising strategy to mitigate the greenhouse effect, yet it remains a challenging process due to the high energy barrier associated with the high stability of CO2. In this study, we synthesized Py-bTDC, a pyrene-based covalent organic framework (COF) enriched with nitrogen and sulfur atoms, and anchored palladium nanoclusters (Pd NCs) onto its structure to enhance CO2 reduction efficiency. The confined Pd NCs amplify the built-in electric field (IEF), enabling efficient photogenerated carrier migration and suppressing electron-hole recombination. Simultaneously, Pd NCs serve as catalytic active sites, optimizing CO2 adsorption and activation. Density functional theory (DFT) calculations reveal that Pd reduces the energy barrier for forming the critical intermediate (*COOH), thereby accelerating CO production. Under visible-light irradiation in a gas-solid system using water as a proton donor, the Pd3/Py-bTDC composite achieved a CO evolution rate of 17.75 μmol·h-1·g-1 with 86.0% selectivity. This study advances the design of COF-based photocatalysts by synergistically modulating IEF and the engineering active sites for efficient CO2 reduction.

The Fabrication of Mesoporous Palladium-Boron Alloy by a Dual-Force-Driven Self-Assembly Strategy for Enhancing the Electrocatalytic Formic Acid Oxidation Activity.

Pd-based catalysts are considered promising for the formic acid oxidation reaction (FAOR), whereas the toxic effect of poisoning intermediates greatly affects the stability and activity of the catalysts. Herein, a dual-force-driven self-assembly strategy is developed to synthesize mesoporous palladium-boron (meso-Pd-B) alloy using cationic polymer polyethyleneimine (PEI) as a pore-forming agent. In this strategy, PEI can interact with the Pd metal precursor via electrostatic and coordination interactions and self-assemble into stable organic-inorganic composites. Dimethylamine borane as a reducing agent together with boric acid enables the alloying of Pd with B, and the Pd-B alloy with mesoporous structure is obtained driven by dual forces. The strategy can be generalized to synthesize other mesoporous metal-B alloys (e.g., Pt-B, Ag-B, Ir-B, Ru-B, and Rh-B). The resultant meso-Pd-B alloy exhibits remarkable catalytic performance (1310 mA mg-1) in FAOR. Combined experimental results and density functional theory calculations indicate that the enhanced activity can be attributed to the electronic effect resulting from the alloying of Pd and B, which weakens the binding strength of toxic substances on the surface of the Pd catalyst. And the favorable mesoporous structure allows the catalyst to expose more catalytic active sites and accelerates the substance transfer efficiency.

Application of Molecular Ferroelectric in Photocatalytic Selective Oxidization of C(sp3)−H Bonds

Molecular ferroelectrics utilize metal nodes and organic groups as catalytic active sites, with the surrounding ferroelectric polarization significantly enhancing catalytic activity and showcasing tremendous application potential. However, their application in photocatalysis remains underexplored. This study presents the first investigation of the molecular perovskite ferroelectric CuCl4‐[R‐MPA] (MPA = β‐methylphenethylamine) as a photocatalyst for alkane oxidation. Under the combined effects of light and ultrasound, this catalyst exhibited a notable turnover number (TON) of 6286 ± 491, which is 10^4 times higher than that of inorganic ferroelectrics like barium titanate (BaTiO3). The molecular ferroelectric exhibits excellent recyclability, good functional group tolerance, and broad substrate applicability. Mechanistic studies indicate that the built‐in electric field within the molecular ferroelectric facilitates the separation of photo‐generated charge carriers, thereby enhancing its ferroelectric photocatalytic activity. Electron paramagnetic resonance (EPR) results further reveal that the synergistic effects of light and ultrasound effectively generate reactive oxygen species. These findings underscore the unique advantages of molecular ferroelectrics compared to rigid inorganic counterparts, including their distinctive structural features and finely tunable catalytic performance, highlighting their potential for developing homogeneous, precisely active sites and efficient photocatalysts. This research lays the foundation for the broader application of molecular ferroelectrics in the field of photocatalysis.

Application of Molecular Ferroelectric in Photocatalytic Selective Oxidization of C(sp3)−H Bonds

Molecular ferroelectrics utilize metal nodes and organic groups as catalytic active sites, with the surrounding ferroelectric polarization significantly enhancing catalytic activity and showcasing tremendous application potential. However, their application in photocatalysis remains underexplored. This study presents the first investigation of the molecular perovskite ferroelectric CuCl4‐[R‐MPA] (MPA = β‐methylphenethylamine) as a photocatalyst for alkane oxidation. Under the combined effects of light and ultrasound, this catalyst exhibited a notable turnover number (TON) of 6286 ± 491, which is 10^4 times higher than that of inorganic ferroelectrics like barium titanate (BaTiO3). The molecular ferroelectric exhibits excellent recyclability, good functional group tolerance, and broad substrate applicability. Mechanistic studies indicate that the built‐in electric field within the molecular ferroelectric facilitates the separation of photo‐generated charge carriers, thereby enhancing its ferroelectric photocatalytic activity. Electron paramagnetic resonance (EPR) results further reveal that the synergistic effects of light and ultrasound effectively generate reactive oxygen species. These findings underscore the unique advantages of molecular ferroelectrics compared to rigid inorganic counterparts, including their distinctive structural features and finely tunable catalytic performance, highlighting their potential for developing homogeneous, precisely active sites and efficient photocatalysts. This research lays the foundation for the broader application of molecular ferroelectrics in the field of photocatalysis.

Interlayer Expanded MXene Film Cathodes with Rich Defects for Flexible 2‐Electron Oxalate‐Based Li–CO2 Batteries: A New Path to Enhanced Energy Efficiency and Durability

AbstractAprotic Li–CO2 batteries have garnered significant attention owing to their high theoretical energy density and potential in zero‐carbon technology. However, their practical application remains hindered by sluggish CO2 reduction/evolution reaction (CRR/CER) kinetics and limited flexibility. While 2D graphene‐like materials are commonly employed to settle these issues, their four‐electron pathway limits efficiency and reversibility. Herein, a defect‐rich, interlayer‐expanded Ti3C2Tx (Ex‐Ti3C2Tx) film cathode is presented for flexible Li–CO2 batteries. The extended interlayer space, reduced ─OH groups, and additional uncoordinated titanium atoms of Ex‐Ti3C2Tx enable abundant catalytic active sites, enhance ion and CO2 transport, and these surface functionalizations suppress interfacial oxidation. Notably, Ex‐Ti3C2Tx stabilizes the bi‐electron product Li2C2O4 via Ti3+/Ti2+ coupling bridges, effectively preventing disproportionation into Li2CO3, thereby significantly improving CRR/CER reversibility and lowering overpotential. Benefiting from these properties, Li–CO2 batteries with Ex‐Ti3C2Tx deliver a remarkable discharge capacity of 3452.33 µAh cm−2, a low polarization potential of 0.39 V, an energy efficiency exceeding 88.9%, and an ultra‐long cycling life (>1600 h). Furthermore, the belt‐shaped flexible battery exhibits excellent flexibility and stable electrochemical performance under deformation highlighting its potential in wearable electronics. This work underscores the critical role of MXene‐based materials in bi‐electron electrocatalytic mechanisms, providing insights for advancing reversible Li–CO2 batteries and flexible energy storage technologies.

Regulating the catalytic active sites of Pd single atom to achieve efficient water splitting

Regulating the catalytic active sites of Pd single atom to achieve efficient water splitting

Graphdiyne based Zn0. 5Cd0. 5S and NiO dual S-scheme heterojunction boosting photocatalytic hydrogen evolution.

Graphdiyne based Zn0. 5Cd0. 5S and NiO dual S-scheme heterojunction boosting photocatalytic hydrogen evolution.

Catalytic Activation Function of Noble-Metal-Free High-Entropy Alloy for Enhancing SnO2 Acetone Detection Capability.

Enhancing the gas-sensing properties of metal oxide semiconductors using noble metals' electronic and chemical sensitization functions is a common approach to develop high-performance gas sensors. However, the high cost and scarcity of noble metals pose challenges to sustainability. In this study, a non-noble metal MnFeCoNiCu high-entropy alloy (HEA) was designed as an alternative to noble metals to enhance the sensitivity of SnO2 and enable efficient, stable, and rapid detection of acetone (C3H6O). The MnFeCoNiCu HEA-loaded SnO2 demonstrated improved performance in C3H6O detection, including high selectivity (κ > 3), a high sensitivity (Ra/Rg = 4.17 at 0.5 ppm), a low detection limit (30 ppb), fast response and recovery time (4.6 s/5 s), long-term stability (over 50 days), and resistance to humidity (stable at 90% RH). The enhanced performance of the HEA is attributed to the fact that it possesses more valence electrons and the electrons can transfer and redistribute among different atoms, which leads to an increase in active oxygen species and catalytic sites, promoting electron sensitization. This study provides insights into designing and developing a highly catalytic, non-noble metal HEA for gas-sensing applications.

Auxiliary Ligand‐Coordinated Nanoconfined Hydrophobic Microenvironments in Nickel(II)–Acetylide Framework for Enhanced CO2 Photoreduction

AbstractMetal–acetylide frameworks (MAFs), featuring metal‐bis(acetylide) linkages (─C≡C─M─C≡C─), are emerging as a new class of 2D nanomaterials with promise in catalysis. Here, we report a new 2D NiII–acetylide framework, TPA‐Ni(PR3)2‐GYs, that incorporates the NiII(PR3)2 moiety [R = CH3 (Me), CH2CH3 (Et), and CH2CH2CH2CH3 (Bu)] into tris(4‐ethynylphenyl)amine‐based graphdiyne framework (TPA‐GDY). As a result, TPA‐Ni(PBu3)2‐GY exhibits an exceptional photocatalytic CO2 reduction activity of 3807 µmol g−1 h−1 and a high selectivity of 99.4% for CO production upon visible light irradiation. Mechanistic investigations reveal a strong orbital matching effect between the d orbitals of NiII and the p orbitals of the alkynyl C atoms in organic ligands, which not only accelerates the transfer and separation of photogenerated charge carriers but also reduces the reaction potential barrier for the formation of *COOH intermediates. Furthermore, the high hydrophobicity of the auxiliary coordinated ligands (trialkylphosphines) to Ni center, particularly tributylphosphine, creates a nanoconfined space that enhances both the accessibility of CO2 and the utilization of NiII catalytic active sites while inhibiting hydrogen evolution. This study highlights the benefit of modulating the microenvironment around the coordinated metal center to enhance the performance of catalysts with direct metal–acetylide bonding.

Boosted photocatalytic activity via photothermal-assisted triphase photocatalysis over an electrospun interpenetrating mat.

Boosted photocatalytic activity via photothermal-assisted triphase photocatalysis over an electrospun interpenetrating mat.

Catalytic Performances of Carbon-Based Tetrel Bond Catalysis by Density Functional Theory and Machine Learning.

The non-covalent interaction catalysis has been widely developed and applied in organocatalysis for its green and economical characteristics in the past decade. In recent years, the carbon-based tetrel bonds have been successfully applied in organocatalysis. In this work, the structure-property relationship of carbon-based tetrel bond catalysts is established by utilizing density functional theory (DFT) and machine learning (ML) techniques. Taking the Michael addition reaction as an example, the reaction mechanism is investigated and new insight into the catalytic active site is introduced based on the DFT-calculated results. The bowl-like 1,1-dicyano-3,3-dicarbonylcyclopropane (DCDC) unit based σ-hole is much more important than the 1,1,2,2-tetracyanocyclopropane (TCCP) unit in tetrel bond catalysts. Moreover, introducing electron-withdrawing groups into carbon-based tetrel catalysts significantly enhances the catalytic activity, which also provides a new strategy for designing efficient catalysts from the perspective of theoretical calculations. Furthermore, the construction and evaluation of ML models demonstrate their potential in predicting the catalyst performance, offering a new protocol for fast prediction of the catalytic performance of tetrel bond catalysts.

Auxiliary Ligand-Coordinated Nanoconfined Hydrophobic Microenvironments in Nickel(II)-Acetylide Framework for Enhanced CO2 Photoreduction.

Metal-acetylide frameworks (MAFs), featuring metal-bis(acetylide) linkages (─C≡C─M─C≡C─), are emerging as a new class of 2D nanomaterials with promise in catalysis. Here, we report a new 2D NiII-acetylide framework, TPA-Ni(PR3)2-GYs, that incorporates the NiII(PR3)2 moiety [R=CH3 (Me), CH2CH3 (Et), and CH2CH2CH2CH3 (Bu)] into tris(4-ethynylphenyl)amine-based graphdiyne framework (TPA-GDY). As a result, TPA-Ni(PBu3)2-GY exhibits an exceptional photocatalytic CO2 reduction activity of 3807µmol g-1h-1 and a high selectivity of 99.4% for CO production upon visible light irradiation.Mechanistic investigations reveal a strong orbital matching effect between the d orbitals of NiII and the p orbitals of the alkynyl C atoms in organic ligands, which not only accelerates the transfer and separation of photogenerated charge carriers but also reduces the reaction potential barrier for the formation of *COOH intermediates. Furthermore, the high hydrophobicity of the auxiliary coordinated ligands (trialkylphosphines) to Ni center, particularly tributylphosphine, creates a nanoconfined space that enhances both the accessibility of CO2 and the utilization of NiII catalytic active sites while inhibiting hydrogen evolution. This study highlights the benefit of modulating the microenvironment around the coordinated metal center to enhance the performance of catalysts with direct metal-acetylide bonding.

Exploring the Mechanisms of Charge Transfer and Identifying Active Sites in the Hydrogen Evolution Reaction Using Hollow C@MoS2-Au@CdS Nanostructures as Photocatalysts.

Plasmonic metal-semiconductor nanocomposites are promising candidates for considerably enhancing the solar-to-hydrogen conversion efficiency of semiconductor-based photocatalysts across the entire solar spectrum. However, the underlying enhancement mechanism remains unclear, and the overall efficiency is still low. Herein, a hollow C@MoS2-Au@CdS nanocomposite photocatalyst is developed to achieve improved photocatalytic hydrogen evolution reaction (HER) across a broad spectral range. Transient absorption spectroscopy experiments and electromagnetic field simulations demonstrate that compared to the treated sample, the untreated sample exhibits a high density of sulfur vacancies. Consequently, under near-field enhancement, photogenerated electrons from CdS and hot electrons generated by intra-band or inter-band transitions of Au nanoparticles are efficiently transferred to the CdS surface, thus significantly improving the HER activity of CdS. Additionally, in situ, Raman spectroscopy provided spectral evidence of S─H intermediate species on the CdS surface during the HER process, which is verified through isotope experiments. Density functional theory simulations identify sulfur atoms in CdS as the catalytic active sites for HER. These findings enhance the understanding of charge transfer mechanisms and HER pathways, offering valuable insights for the design of plasmonic photocatalysts with enhanced efficiency.

Binding interaction of acetylcholinesterase with steroidal pregnanes: insight from machine learning and atomistic simulation

Acetylcholinesterase (AChE) inhibition is a key strategy in the treatment of Alzheimer’s disease and other neurodegenerative disorders. While pregnane-based compounds have been suggested as AChE inhibitors, their mechanism of action remains unclear. This study employed machine learning (ML) and molecular modeling to probe the molecular interaction of AChE with steroidal pregnanes. The ML models were trained and validated on AChE bioactivity datasets to predict pIC50 and pKi values of small-molecule compounds. Among the models tested, the Random Forest Regressor demonstrated superior performance and was used to identify pregnanes with pIC50 ≥ 5 and pKi ≥ 7 as promising inhibitors. Molecular docking revealed strong molecular interactions between AChE and several pregnanes, particularly 21-[(3-Hydroxy-2-naphthyl)oxy]pregnane-2-one. This compound interacted with critical sub-sites within the AChE binding gorge, including the catalytic active site, peripheral anionic site, oxyanion hole, and anionic sub-site, through multiple hydrogen bonds and hydrophobic interactions. Molecular dynamics simulations over 100 ns indicated structural stability and conformational flexibility of representative AChE-pregnane complexes as indicated by the dynamic parameters and cluster patterns. The Molecular Mechanics with Generalized Born Surface Area free energy analysis confirmed strong binding affinities, while residual energy decomposition provided insights into key residue contributions. Additionally, the pregnanes demonstrated favorable blood-brain barrier permeability and other drug-like properties, suggesting their potential as neurotherapeutic agents. Given their predicted bioactivity, strong interactions with AChE, and drug-like properties, the identified pregnanes warrant further optimization and experimental evaluation for the development of safe and effective AChE inhibitors.

Bio‐Inspired In Situ Tuning of the Hydrophobic Environment Around Catalytically Active Organic Ligand‐Stabilized Ruthenium Nanoparticles

AbstractThe organic ligand environment surrounding enzymatic and homogeneous catalytic active sites often determines catalytic activity. Ruthenium nanoparticles, ≤1 nm in diameter, are synthesized using monodentate thiol, monodentate phosphine, and bidentate bisphosphine ligands. Even though some of the ruthenium surface is blocked by the ligands, catalytic activity is still observed for CO oxidation and H2O2 decomposition. All three ligand‐stabilized ruthenium nanoparticles have similar CO oxidation rates; however, the bisphosphine‐stabilized Ru nanoparticles are approximately 2.5 times less active than the monothiol‐stabilized and monophosphine‐stabilized ruthenium nanoparticles for H2O2 decomposition. It is observed that the organic ligand environment is modulated in situ during nanoparticle synthesis via partial oxidation of the bisphosphine as confirmed by 31P NMR measurements. We hypothesize that bisphosphine‐bound Ru nanoparticles consist of a Ru core with some of the ligands bound in a monodentate manner where the other P atom is oxidized and not bound to the Ru surface leading to a thicker hydrophobic layer around the Ru nanoparticles. The increase in hydrophobicity is confirmed via contact angle and zeta potential measurements. H2O2 decomposition rates are known to decrease with increasing hydrophobicity, and this work illustrates a pathway for increasing hydrophobicity in situ using ligand‐bound metallic nanoparticles.

Nanoarchitectonics of Palladium Nanoparticles Supported on Carbon‐Based Heterogeneous Catalysts for C─H Activation Reaction

AbstractOrganic reactions involving the direct functionalization of non‐activated C─H bonds represent a valuable class of transformations, enhancing atom, and step economy while streamlining chemical synthesis. However, the high stability of C─H bonds often necessitate harsh reaction conditions, significantly limiting their application in synthesizing complex organic molecules. In order to break the inert C─H bond and convert it into the useful C─C, C─O, C─X, and C─N conversion under benign conditions, several active and selective catalytic systems have been designed. Metal (Pd)‐supported carbon‐based heterogeneous catalysts offer a promising approach in this context. Different type of support such as graphene oxide, reduced graphene oxide and carbon nanotubes are used as a support material. Pd(II) species activates the C─H bond, and involved in an oxidation and reduction cycle involving insertion to the substrate and regeneration of catalytic active site. The activation of C─H bonds in hydrocarbons involves the insertion of a metal into the C─H bond resulting in the formation of an organometallic complex which then reacts with another substrate (reaction partner) to yield the final product. Sometime the efficiency of Pd metal can be increased by using another metal which helps to reduce the HOMO–LUMO gap and stabilize the catalyst. Therefore, this minireview discuss the most recent advancement of Pd supported on carbon based heterogeneous catalyst for C─H bond activation.