Catalyst Architecture Research Articles

Porous N-Doped Carbon-encapsulated Iron as Novel Catalyst Architecture for the Electrocatalytic Hydrogenation of Benzaldehyde.

Carbon porous materials containing nitrogen functionalities and encapsulated iron-based active sites have been suggested as electrocatalysts for energy conversion, however their applications to the hydrogenation of organic substrates via electrocatalytic hydrogenation (ECH) remain unexplored. Herein, we report on a Fe@C:N material synthesized with an adapted annealing procedure and tested as electrocatalyst for the hydrogenation of benzaldehyde. Using different concentrations of the organic, and electrolysis coupled to gas chromatography experiments, we demonstrate that it is possible to use such architectures for the ECH of unsaturated organics. Potential control experiments show that ECH faradaic efficiencies >70 % are possible in acid electrolytes, while maintaining selectivity for the alcohol over the pinacol dimerization product. Estimates of product formation rates and turnover frequency (TOF) values suggest that these carbon-encapsulated architectures can achieve competitive performance in acid electrolytes relative to both base and precious metal electrodes.

Step-Scheme SnO₂/Zn₃In₂S₆ Catalysts for Solar Production of Hydrogen Peroxide From Seawater.

Photocatalytic generation of H₂O₂, involving both oxygen reduction and water oxidation without sacrificial agents, necessitates maximized light absorption, suitable band structure, and efficient carrier transport. Leveraging the redox capacity this study designs and constructs a step-scheme heterostructured SnO₂/Zn₃In₂S₆ catalyst for H₂O₂ production from seawater under ambient conditions for the first time. This photocatalyst demonstrates a remarkable H₂O₂ production rate of 43.5µmol g⁻¹ min⁻¹ without sacrificial agents, which can be increased to 80.7µmol g⁻¹ min⁻¹ with additional O₂ injection. Extensive in situ and ex situ characterizations, supported by theoretical calculations, reveal efficient carrier transport and robust redox ability, enabling complete photosynthesis of H₂O₂ at the oxidation and reduction sites in the S-scheme SnO₂/Zn₃In₂S₆ heterojunction. Furthermore, it is hypothesized that substituting SnO₂ with other semiconductors such as TiO₂, WO₃, and BiVO₄ can all form S-scheme and the results confirm the feasibility of such catalyst design. Additionally, it demonstrates the recycling and further utilization of the H₂O₂ produced. These findings offer new insights into the design of heterostructure catalyst architectures and present new opportunities for H₂O₂ production from seawater at ambient conditions without sacrificial agents.

Synergistic Interactions of Bulk Polarization and Built-In Electric Field Inducing 2D/2D S-Scheme Homojunction Toward Enhanced Photocatalytic Performance.

The rational design of S-scheme photocatalysts, achieved by serially integrating two different semiconductors, represents a promising strategy for efficient charge separation and amplified photocatalytic performance, yet it remains a challenge. Herein, ZnIn2S4 (ZIS) and oxygen-doped ZnIn2S4 (O-ZIS) nanosheets are chosen to construct a homojunction catalyst architecture. Theoretical simulations alongside comprehensive in situ and ex situ characterizations confirm that ZIS and O-ZIS with noncentrosymmetric layered structures can generate a polarization-induced bulk-internal electric field (IEF) within the crystal. A robust interface-IEF is also created by the strong interfacial interaction between O-ZIS and ZIS with different work functions. Owing to these features, the O-ZIS/ZIS homojunction adopts an S-scheme directional charge transfer route, wherein photoexcited electrons in ZIS and holes in O-ZIS concurrently migrate to their interface and subsequently recombine. This enables spatial charge separation and provides a high driving force for both reduction and oxidation reactions simultaneously. Consequently, such photocatalyst exhibits an H2 evolution rate up to 142.9µmol h-1 without any cocatalysts, which is 4.6- and 3.4-fold higher than that of pristine ZIS and O-ZIS, respectively. Benzaldehyde is also produced as a value-added oxidation product with a rate of 146.9µmol h-1. This work offers a new perspective on the design of S-scheme systems.

In situ construction of sequential nanoreactor with built-in catalyst as self-supporting cathode for lithium–sulfur batteries

Architecture design and optimization are essential in improving the performance of lithium–sulfur batteries. Herein, an all-in-one sequential architecture of CoSe catalysts confined in MOF-derived nanoreactors (NRs) interfacially welded on carbon cloth (CC) is constructed using an in situ strategy (abbreviated: S@CoSe-NRs/CC). NRs with built-in CoSe (CoSe-NRs) have special microenvironments and domain-limited catalysis for efficient adsorption, catalysis, and deposition. The weld interface between the CoSe-NRs and the CC forms a continuous and robust all-in-one conductive network. Both experiments and theoretical calculations demonstrate that the S@CoSe-NRs/CC offers stable interconnectivity and efficient space utilization for high sulfur loads and rapid ion transport supply, providing a high initial discharge capacity of 1320 mA h g−1 at 0.1 C with a capacity decay rate as low as 0.003% per turn after 1000 cycles. This study offers unique insights and revelations for realizing the rational design of high-performance energy storage devices.

Controlled Catalyst Layer Architectures for Fuel Cell Applications

The catalyst layer composition and architecture play a pivotal role in bridging the gaps between ex situ and in situ catalyst activities in fuel cells.1 The catalyst-support architecture strongly influences the catalyst distribution, ionomer distribution and mass transport losses, occurring at high current density.2 Herein, a novel architecture based on self-standing fiber-network has been fabricated and characterized.3 The resulting porous structure of such catalyst layer is expected to control mass transport limitation across both the interface of catalyst layer by increasing the number of Triple Phase Boundaries. Further platinum catalyst is deposited onto this fibrous support as well as the ionomer. The full electrode is characterized for its morphology and electrochemically verified in both ex situ as well as in situ configurations. References (1) Jiantao Fan, Ming Chen, Zhiliang Zhao, Zhen Zhang, Siyu Ye, Shaoyi Xu, Haijiang Wang & Hui Li, “Bridging the Gap between Highly Active Oxygen Reduction Reaction Catalysts and Effective Catalyst Layers for Proton Exchange Membrane Fuel Cells”, Nature Energy, 6, 475–486, (2021).(2) Nagappan Ramaswamy, Wenbin Gu, Joseph M. Ziegelbauer and Swami Kumaraguru, “Carbon Support Microstructure Impact on High Current Density Transport Resistances in PEMFC Cathode”, Journal of The Electrochemical Society ,167, 064515, 2020.(3) Giorgio Ercolano, Filippo Farina, Sara Cavaliere, Deborah J. Jones and Jacques Rozière, “Towards Ultrathin Pt Films on Nanofibers by Surface-Limited Electrodeposition for Electrocatalytic Applications”, Journal of Materials Chemistry A , 5, 3974–3980, 2017.

Role of morphology in improving the catalytic performance of ZnCo2O4 for soot oxidation

The extent of interaction between carbon and catalyst profoundly shapes soot oxidation results. The catalyst configuration notably influences the frequency of contact points in solid–solid interactions. This investigation studies the impact of three distinct ZnCo2O4 catalyst morphologies and their redox property on soot oxidation. The formation of the cubic phase of ZnCo2O4 via three distinct methods was revealed during XRD analysis. SEM analysis unveiled varying morphologies, including rod-shaped, rose petal-shaped, and bead-like structures. Notably, ZnCo2O4 exhibiting bead-like morphology demonstrated heightened levels of chemisorbed oxygen species which was observed during XPS analysis. The presence of Co2+ and Co3+ occupied at octahedral site ZnCo2O4 acted as the active sites for soot oxidation. With continuous redox property (Co 3+ → Co 2+) leading to the generation of active oxygen species and with an added advantage of surface morphology, the M2 sample (with bead-like morphology) exhibited superior soot oxidation activity, which is evident by its T50% value of 402 °C. This study underscores the essential role of catalyst morphology in influencing soot oxidation activity. Through a comprehensive array of structural, morphological, and catalytic analyses, this work sheds light on the correlation between catalyst architecture and enhanced soot oxidation performance.

Tailoring Cu-SiO2 Interaction through Nanocatalyst Architecture to Assemble Surface Sites for Furfural Aqueous-Phase Hydrogenation to Cycloketones.

In this contribution, nanocatalysts with rather diverse architectures were designed to promote different intimacy degrees between Cu and SiO2 and consequently tune distinct Cu-SiO2 interactions. Previously synthesized copper nanoparticles were deposited onto SiO2 (NPCu/SiO2) in contrast to ordinarily prepared supported Cu/SiO2. NPCu@SiO2 and SiO2@Cu core-shell nanocatalysts were also synthesized, and they were all bulk and surface characterized by XRD, TGA, TEM/HRTEM, H2-TPR, XANES, and XPS. It was found that Cu0 is the main copper phase in NPCu/SiO2 while Cu2+ rules the ordinary Cu/SiO2 catalyst, and Cu0 and electron-deficient Cuδ+ species coexist in the core-shell nanocatalysts as a consequence of a deeper metal-support interaction. Catalytic performance could not be associated with the physical properties of the nanocatalysts derived from their architectures but was associated with the more refined chemical characteristics tuned by their design. Cu/SiO2 and NPCu/SiO2 catalysts led to the formation of furfuryl alcohol, evidencing that catalysts holding weak or no metal-support interaction have no significant impact on product distribution even in the aqueous phase. The establishment of such interactions through advanced catalyst architecture, allowing the formation of electron-deficient Cuδ+ moieties, particularly Cu2+ and Cu+ as unveiled by spectroscopic investigations, is critical to promoting the hydrogenation-ring rearrangement cascade mechanism leading to cycloketones.

Iso‐Elemental ZnIn2S4/Zn3In2S6 Heterojunction with Low Contact Energy Barrier Boosts Artificial Photosynthesis of Hydrogen Peroxide

AbstractArtificial photosynthesis emerges as a strategic pathway to produce hydrogen peroxide (H2O2), an environmentally benign oxidant and a clean energy carrier. Nonetheless, in many heterojunction‐based artificial photosynthetic systems, the H2O2 productivity is significantly hindered by poor carrier transport, narrow spectral light absorption, and a lack of adequate active sites for the two‐electron oxygen reduction reaction. Herein, a catalyst architecture with an iso‐elemental heterojunction formed by interfacing Zn3In2S6 nano‐flowers and ZnIn2S4 nanosheets is proposed. This catalyst exhibits a H2O2 production rate as high as 23.47 µmol g−1 min−1 under UV–vis light irradiation, which is attributed to the minimized contact energy barrier and enhanced lattice match at the ZnIn2S4/Zn3In2S6 interface thanks to the iso‐elemental catalyst architecture which aids in enhanced efficient separation and transfer of photogenerated carriers. Theoretical simulations alongside comprehensive in‐situ and ex‐situ characterizations confirm the photo‐redox sites for H2O2 generation and effective carrier dynamics across the catalyst surface. Moreover, substituting one reduction‐type catalyst ZnIn2S4 with other non‐iso‐elemental catalysts like CdIn2S4, TiO2, and CdS further confirms the feasibility and superiority of the proposed iso‐elemental configuration. This work offers a new perspective on designing heterojunction catalysts for artificial photosynthesis of H2O2.

SEM Image Processing Assisted by Deep Learning to Quantify Mesoporous γ-Alumina Spatial Heterogeneity and Its Predicted Impact on Mass Transfer.

The pore network architecture of porous heterogeneous catalyst supports has a significant effect on the kinetics of mass transfer occurring within them. Therefore, characterizing and understanding structure-transport relationships is essential to guide new designs of heterogeneous catalysts with higher activity and selectivity and superior resistance to deactivation. This study combines classical characterization via N2 adsorption and desorption and mercury porosimetry with advanced scanning electron microscopy (SEM) imaging and processing approaches to quantify the spatial heterogeneity of γ-alumina (γ-Al2O3), a catalyst support of great industrial relevance. Based on this, a model is proposed for the spatial organization of γ-Al2O3, containing alumina inclusions of different porosities with respect to the alumina matrix. Using original, advanced SEM image analysis techniques, including deep learning semantic segmentation and porosity measurement under gray-level calibration, the inclusion volume fraction and interphase porosity difference were identified and quantified as the key parameters that served as input for effective tortuosity factor predictions using effective medium theory (EMT)-based models. For the studied aluminas, spatial porosity heterogeneity impact on the effective tortuosity factor was found to be negligible, yet it was proven to become significant for an inclusion content of at least 30% and an interphase porosity difference of over 20%. The proposed methodology based on machine-learning-supported image analysis, in conjunction with other analytical techniques, is a general platform that should have a broader impact on porous materials characterization.

Charge Redistribution of Lattice-Mismatched Co─Cu3P Boosting pH-Universal Water/Seawater Hydrogen Evolution.

Practical applications of the hydrogen evolution reaction (HER) rely on the development of highly efficient, stable, and low-cost catalysts. Tuning the electronic structure, morphology, and architecture of catalysts is an important way to realize efficient and stable HER electrocatalysts. Herein, Co-doped Cu3P-based sugar-gourd structures (Co─Cu3P/CF) are prepared on copper foam as active electrocatalysts for hydrogen evolution. This hierarchical structure facilitates fast mass transport during electrocatalysis. Notably, the introduction of Co not only induces a charge redistribution but also leads to lattice-mismatch on the atomic scale, which creates defects and performs as additional active sites. Therefore, Co─Cu3P/CF requires an overpotential of only 81, 111, 185, and 230mV to reach currents of 50, 100, 500, and 1000mA cm-2 in alkaline media and remains stable after 10 000 CV cycles in a row and up to 110h i-t stability tests. In addition, it also shows excellent HER performance in water/seawater electrolytes of different pH values. Experimental and DFT show that the introduction of Co modulates the electronic and energy level structures of the catalyst, optimizes the adsorption and desorption behavior of the intermediate, reduces the water dissociation energy barrier during the reaction, accelerates the Volmer step reaction, and thus improves the HER performance.

Bifunctional Mo4O11 Nanosheets-Engineered Co-Ni alloy nanowires enable High-Efficiency seawater electrolysis and Zn-Seawater battery

This study reports an electrocatalyst derived from multi-valent Mo4O11 nanosheets coupled Co-Ni (CN) nanowires (NW) (denoted as CN@Mo4O11) with improved catalytic coherency for both high-performance seawater splitting and Zn-seawater battery. The CN@Mo4O11 material significantly enhances the catalytical activity with a low overpotential of 63 mV/69 mV for hydrogen evolution and 100 mV/120 mV for oxygen evolution, respectively, to attain 10 mA⋅cm−2 in alkaline freshwater/seawater. An electrolyzer cell of CN@Mo4O11(+,-) exhibits a low cell voltage of 1.40 V/1.44 V at 10 mA‧cm−2 during alkaline freshwater/seawater splitting with an excellent performance retention of 98.6 %/97.6 % after a long-term operation for 50 h. The solar cell coupled electrolyzer also delivers a high solar to hydrogen conversion efficiency of 15.54 %/16.1 % in alkaline freshwater/seawater. A Zn-seawater battery based on CN@Mo4O11 cathode also delivers high current and power densities of 82 mA‧cm−2 and 27.6 mW‧cm−2, respectively, with a stable discharge time of 40 h. The CN@Mo4O11 heterostructure imparts favorable density of states and optimized adsorption energy for HER and OER, as deduced from DFT calculations, leading to improved overall catalytic performance and corrosion resistance in seawater. Results of this work clearly prove that this proposed catalyst architecture indeed has a huge potential for both seawater splitting and Zn-seawater battery fabrication.

Unravelling the Influence of Binder Typology during the Additive Manufacturing of Hybrid Multi-Channel Cylinders for Catalytic Purposes

In this work, a 3D printing methodology based on the robocasting of catalytic ink pastes was applied to obtain structured matrix-like cylinders as innovative materials for an effective utilization of carbon dioxide. The influence of three different binders (i.e., PEI, HPMC and MC) on the physio-chemical, mechanical and catalytic properties of multi-channel monoliths was studied against a reference binder-free powdered system in order to envisage the effectiveness of the printing procedure in realizing hybrid advanced materials at a higher control and reproducibility than from traditional preparation techniques. In terms of textural and structural properties, the micro-extruded 3D cylinders only evidenced a slight difference in terms of relative crystallinity, with minor effects on the surface area exposure in relation to the specific binder used during the direct ink writing process. More importantly, the typology of binder significantly affected the rheological properties of the catalytic ink, with the need of a controlled viscosity to ensure a suitable thixotropic behaviour of the extrudable pastes, finally determining an optimal mechanical resistance of the final 3D monolith. The experimental validation of the hybrid multi-channel cylinders under conditions of CO2 hydrogenation demonstrated the great potential of additive manufacturing in the realization of catalyst architectures characterized by unique features and fidelity scarcely reproducible via conventional synthetic techniques.

Synergistic Effect of CNT-TiO2 Catalyst and 3D Electrode Architecture for Electrochemical Performance in Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are a potential electrochemical storage system for the future with high capacity (1675 mAh g−1) and energy density (∼2600 Wh kg−1). The poor conductivity of sulfur, polysulfide shuttle effect, and volume expansion of the sulfur cathode are the main hurdles to their commercialization. To mitigate these issues, this work represents a rational composite of hybrid multiwalled carbon nanotubes (MWCNT) -TiO2 high surface area carbon-sulfur composite (CTHS) onto a 3D carbon fiber (CF) based free-standing electrode (CTHS@CF) architecture. TiO2 can effectively anchor the polysulfides by chemical bonding and improve cyclability. MWCNTs and CFs are the effective electron transport materials that accelerate the redox kinetics of polysulfides. The electrochemistry of CTHS@CF reveals an excellent discharge capacity of 910 mAh g−1 (1st cycle) at 100 mA g−1 compared to the conventional aluminum-coated (CTHS@Al) of 532 mAh g−1. The CTHS@CF (at 300 mA g−1) displays 514 mAh g−1 (initial discharge) capacity with 83% capacity retention up to 100 cycles, whereas CTHS@Al shows 394 mAh g−1 with 44% capacity retention. Combining 3D electrode architecture with the metal oxide (TiO2) plays a vital role in the electrochemistry of LSBs by improving the stability of the battery’s cycle life and overall energy density.

Catalyst architecture for metal–support interactions and its effects on heterogeneous reactions

Metal nanoparticles supported on various metal oxides play vital roles in numerous industrial catalytic reactions.

High-density accessible Ru[sbnd]O[sbnd]Co moieties with accelerated formation of activated oxygen species for freshwater and seawater electrolysis

Promoting the activated oxygen formation and the accessible site density is crucial for boosting the mass and price activity of Ru in water/seawater electrolysis. However, a rational catalyst architecture is lacking to satisfy the above requirements. Herein, Ru was intentionally embedded into few-layer Co3O4 (Ru-Co3O4) to construct high-density accessible RuOCo moieties for water/seawater splitting. The moiety structure accelerates the generation and dissociation of activated H2O during hydrogen evolution reaction (HER), and ensures the rapid evolution of key “activated oxygen” species in oxygen evolution reaction (OER), thus improving HER/OER intrinsic kinetics. Besides, these moieties embedded within few-layer structure effectively promote site formation and utilization. Consequently, compared with Ru/C and Pt/C, an order of magnitude increase in mass and price activity was achieved for bifunctional HER/OER. When applied in an anion-exchange-membrane (AEM) electrolyzer, this catalyst realizes industrial-level current densities for freshwater and seawater electrolysis, more than twice than Ru/C(+)||Pt/C(−), and robust durability.

Dual-active-component assembly catalyst based continuous flow system for organic reactions with high processing rate

Designing and fabricating suitable packing catalyst with high activity and low flow resistance for continuous flow system is highly desirable but remains a grand challenge. Here we report a facile one-pot strategy to synthesize a dual-active-component assembly catalyst (DACAC) with N-doped holey graphene (NHG) anchored single-atom Pd (Pd1) self-assembled on fibrous aluminum silicate cluster (FASC) skeleton. The resultant Pd1/NHG–FASC DACAC possesses dual-active-components (i.e., Pd atoms and NHG) and hierarchical architecture and can be easily integrated into a fixed-bed platform to construct a catalytic continuous flow system. This fixed-bed system based on the assembly catalyst architecture effectively drives continuous flow reactions with excellent catalytic efficiency for nitroarene reduction and phenylboronic acid oxidative hydroxylation reactions. The processing rate for catalytic reduction of 4-nitrophenol is 1.5 × 10–3 mmol·mg−1·min−1, which is much higher than that of other previously reported packing catalysts based fixed-bed systems. The activity enhancement strategy of dual-active-component provides a new approach to design highly efficient catalytic materials.

Enzyme-mimetic catalyst architectures: the role of second coordination sphere in catalytic activity

Abstract Enzymes with well-defined three-dimensional structure have in-built information for molecular organization in the near vicinity of the active sites—popularly known as enzyme architecture. Over the past few years, molecular assembly has been exploited in creating artificial enzyme or catalyst architectures. Emergent spatiotemporal structure and catalytic activity can be achieved through controlled assembly of suitable molecular building blocks. The programmed molecular assembly governed by the scheme of molecule architectonics can generate enzyme-mimetic catalyst assembly architecture. Apart from the conventional ligand-metal interaction in the first coordination sphere of a catalyst, a second coordination sphere plays a key role in the catalytic activity of enzymes. This review attempts to unravel the balancing act between molecular architectonics and second coordination spheres in catalyst assembly architecture development. Judicious design and exploitation of state-of-the-art biomimetic catalyst architecture derived from small molecules, sugars, nucleic acids, peptides, and proteins are discussed under the above-mentioned framework. Metal-coordinated molecular assembly architectures of specific catalytic properties are considered with respect to the nature of molecular assembly and experimental conditions. The concise and critical discussion provides a holistic view of enzyme-mimetic architectures and their second coordination spheres through a reductionistic approach based on the molecular architectonics of simple and modular molecular building blocks.

Enzyme-mimetic Catalyst Architectures: The Role of Second Coordination Sphere in Catalytic Activity

Enzyme-mimetic Catalyst Architectures: The Role of Second Coordination Sphere in Catalytic Activity

Tailoring high-performance catalyst architectures via ‘accessional ionomer coatings’ for anion exchange membrane water electrolysis

Anion exchange membrane water electrolysis (AEMWE) represents a viable solution for achieving large-scale, low-cost hydrogen production. The catalyst and ionomer layers play a crucial role in facilitating the electrochemical reactions on the electrodes in AEMWE. However, the optimization of catalyst-ionomer configurations through architectural and structural development remains an understudied area of research, despite its critical importance. Here, this study involved the preparation and investigation of multiple catalyst-ionomer configurations, including those with single and dual ionomer layers at both the cathode and anode. Our findings indicate that incorporating an additional ionomer layer in the catalyst-coated membrane-based membrane electrode assemblies (MEAs) improve their performance by enhancing interfacial contact area and facilitating charge transfer, compared to MEA configurations without ionomer layers. While ionomer-modified catalyst-coated substrate-based MEA configurations do not show a significant improvement in activity, they demonstrate lower potentials during a 150-h stability test. Furthermore, cost-effective MEAs are fabricated by replacing noble metal anode catalysts with commercially available NiFe nanoparticles, which exhibit comparable catalytic activity and enhanced durability.

ZrO2 promoted Ru/In2O3 catalyst for selective hydrogenation of CO2 to methanol

With the strong metal-support interaction, In2O3 supported Ru catalyst has been confirmed to be active for selective hydrogenation of CO2 to methanol. Herein, we report that the addition of ZrO2 into Ru/In2O3 further improves the catalytic activity for CO2 hydrogenation to methanol. The catalyst characterization shows a formation of In2O3-ZrO2 solid solution, which is an excellent support for the highly dispersed Ru catalyst. Compared to Ru/In2O3, a significantly higher methanol selectivity is achieved over the Ru/In2O3-ZrO2 catalyst with 1 wt% Ru loading. The methanol space–time yield (STY) reaches 0.685 gMeOH h−1 gcat−1 at 300 ℃, 5 MPa, and 21000 cm3 gcat−1h−1. It has more than 20% increase compared to Ru/In2O3. The addition of ZrO2 optimizes the oxygen vacancies of In2O3, improves the CO2 adsorption and enables a more stable catalyst architecture, while the hydrogen spillover by the highly dispersed ruthenium improves the hydrogen activation ability of the catalyst. All these results in a high level of methanol yield.