Cross‐Linked Surface Engineering to Improve Iron Porphyrin Catalytic Activity

Quasi‐two‐dimensional (QTD) structural heterogeneous catalysts have attracted a broad interest in multidisciplinary research due to their unique structure, preeminent surface properties and outstanding catalytic performance. Herein, a HZIF@TCPP‐Fe/Fe heterogeneous catalyst based on cross‐linked surface engineering is constructed by supporting QTD TCPP‐Fe/Fe ultra‐thin metallized film (≈2 nm) on hollow skeleton of zeolite imidazolate frameworks. The designed QTD structure exhibits high efficiency for the catalytic oxidative dehydrogenation of aromatic hydrazides reactions which is the key technology in various industrial processes. Taking advantage of QTD structure with excellent accessibility, the metallized film with irregular defects not only enhances electron transfer during the reaction but also exposes more surface‐active sites. Furthermore, the prepared HZIF@TCPP‐Fe/Fe heterogeneous catalyst can be recycled and reused, which is of great significance in the field of green chemistry.     

Highly Robust Non‐Noble Alkaline Hydrogen‐Evolving Electrocatalyst from Se‐Doped Molybdenum Disulfide Particles on Interwoven CoSe2 Nanowire Arrays

Developing efficient non‐noble and earth‐abundant hydrogen‐evolving electrocatalysts is highly desirable for improving the energy efficiency of water splitting in base. Molybdenum disulfide (MoS₂) is a promising candidate, but its catalytic activity is kinetically retarded in alkaline media due to the unfavorable water adsorption and dissociation feature. A heterogeneous electrocatalyst is reported that is constructed by selenium‐doped MoS₂ (Se‐MoS₂) particles on 3D interwoven cobalt diselenide (CoSe₂) nanowire arrays that drives the hydrogen evolution reaction (HER) with fast reaction kinetics in base. The resultant Se‐MoS₂/CoSe₂ hybrid exhibits an outstanding catalytic HER performance with extremely low overpotentials of 30 and 93 mV at 10 and 100 mA cm^–2 in base, respectively, which outperforms most of the inexpensive alkaline HER catalysts, and is among the best alkaline catalytic activity reported so far. Moreover, this hybrid catalyst shows exceptional catalytic performance with very low overpotentials of 84 and 95 mV at 10 mA cm^–2 in acidic and neutral electrolytes, respectively, implying robust pH universality of this hybrid catalyst. This work may provide new inspirations for the development of high‐performance MoS₂‐based HER electrocatalysts in unfavorable basic media for promising catalytic applications.     

Ultrafine Nanoparticle‐Supported Ru Nanoclusters with Ultrahigh Catalytic Activity

The design of an ideal heterogeneous catalyst for hydrogenation reaction is to impart the catalyst with synergetic surface sites active cooperatively toward different reaction species. Herein a new strategy is presented for the creation of such a catalyst with dual active sites by decorating metal and metal oxide nanoparticles with ultrafine nanoclusters at atomic level. This strategy is exemplified by the design and synthesis of Ru nanoclusters supported on Ni/NiO nanoparticles. This Ru‐nanocluster/Ni/NiO‐nanoparticle catalyst is shown to exhibit ultrahigh catalytic activity for benzene hydrogenation reaction, which is 55 times higher than Ru–Ni alloy or Ru on Ni catalysts. The nanoclusters‐on‐nanoparticles are characterized by high‐resolution transmission electron microscope, Cs‐corrected high angle annular dark field‐scanning transmission electron microscopy, elemental mapping, high‐sensitivity low‐energy ion scattering, and X‐ray absorption spectra. The atomic‐scale nanocluster–nanoparticle structural characteristics constitute the basis for creating the catalytic synergy of the surface sites, where Ru provides hydrogen adsorption and dissociation site, Ni acts as a “bridge” for transferring H species to benzene adsorbed and activated at NiO site, which has significant implications to multifunctional nanocatalysts design for wide ranges of catalytic reactions.     

Heterogeneous Single‐Atom Catalyst for Visible‐Light‐Driven High‐Turnover CO2 Reduction: The Role of Electron Transfer

Visible‐light‐driven conversion of CO₂ into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single‐atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO₂ conversion, wherein the graphene bridges homogeneous light absorbers with single‐atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min^?1, superior to those obtained with the state‐of‐the‐art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO₂ conversion from the angle of single‐atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts.     

Use of 3D printing for biofuel production: efficient catalyst for sustainable biodiesel production from wastes

This work deals with the sustainable biodiesel production from low-cost renewable feedstock (waste and non-edible oils) using a heterogeneous catalyst constituted by potassium loaded on an amorphous aluminum silicate naturally occurring as volcanic material (pumice). The main challenge to biodiesel production from low-quality oils (used oils and greases) is the high percentage of free fatty acids (FFAs) and water in the feedstock that causes undesirable side reactions. The catalytic materials studied were tested in the transesterification reaction when using low-quality oils containing a high proportion of free fatty acids (FFAs) and water. Results indicated that the amount of acid and basic sites on the catalytic surface increases upon increasing potassium loading in the catalyst, displaying better performance for biodiesel production. Indeed, the modification of the aluminum silicate substrate upon potassium incorporation results in a catalytic material containing both acidic and basic sites, which are responsible for both triglycerides transesterification and FFA esterification reactions. The studied catalyst not only showed good performance in the biodiesel production reaction but also good tolerance to FFA and water contained in the feedstock for biodiesel production. The catalytic material was microstructured by 3D printing in order to design a catalytic stirring system with high mechanical strength, efficient and reusable. The use of 3D printing in biofuel production is a novelty that brings good solutions for catalyst production.     

Site‐Selective Catalysis of a Multifunctional Linear Molecule: The Steric Hindrance of Metal–Organic Framework Channels

The site‐selective reaction of a multifunctional linear molecule requires a suitable catalyst possessing both uniform narrow channel to limit the molecule rotation and a designed active site in the channel. Recently, nanoparticles (NPs) were incorporated in metal–organic frameworks (MOFs) with the tailorable porosity and ordered nanochannel, which makes these materials (NPs/MOFs) highly promising candidates as catalytic nanoreactors in the field of heterogeneous catalysis. Inspired by a “Gondola” sailing in narrow “Venetian Canal” without sufficient space for a U‐turn, a simple heterogeneous catalyst based on NPs/MOFs is developed that exhibits site‐selectivity for the oxidation of diols by restricting the random rotation of the molecule (the “Gondola”) in the limited space of the MOF channel (the narrow “Venetian Canal”), thereby protecting the middle functional group via steric hindrance. This strategy is not limited to the oxidation of diols, but can be extended to the site‐selective reaction of many similar multifunctional linear molecules, such as the reduction of alkadienes.     

Well‐Defined Cobalt Catalyst with N‐Doped Carbon Layers Enwrapping: The Correlation between Surface Atomic Structure and Electrocatalytic Property

Admittedly, the surface atomic structure of heterogenous catalysts toward the electrochemical oxygen reduction reaction (ORR) are accepted as the important features that can tune catalytic activity and even catalytic pathway. Herein, a surface engineering strategy to controllably synthesize a carbon‐layer‐wrapped cobalt‐catalyst from 2D cobalt‐based metal–organic frameworks is elaborately demonstrated. Combined with synchrotron radiation X‐ray photoelectron spectroscopy, the soft X‐ray absorption near‐edge structure results confirmed that rich covalent interfacial Co? N? C bonds are efficiently formed between cobalt nanoparticles and wrapped carbon‐layers during the polydopamine‐assisted pyrolysis process. The X‐ray absorption fine structure and corresponding extended X‐ray absorption fine structure spectra further reveal that the wrapped cobalt with Co–N coordinations shows distinct surface distortion and atomic environmental change of Co‐based active sites. In contrast to the control sample without coating layers, the 800 °C‐annealed cobalt catalyst with N‐doped carbon layers enwrapping achieves significantly enhanced ORR activity with onset and half‐wave potentials of 0.923 and 0.816 V (vs reversible hydrogen electrode), highlighting the important correlation between surface atomic structure and catalytic property.     

Robust Catalysis on 2D Materials Encapsulating Metals: Concept,Application, and Perspective

Great endeavors are undertaken to search for low‐cost, rich‐reserve, and highly efficient alternatives to replace precious‐metal catalysts, in order to cut costs and improve the efficiency of catalysts in industry. However, one major problem in metal catalysts, especially nonprecious‐metal catalysts, is their poor stability in real catalytic processes. Recently, a novel and promising strategy to construct 2D materials encapsulating nonprecious‐metal catalysts has exhibited inimitable advantages toward catalysis, especially under harsh conditions (e.g., strong acidity or alkalinity, high temperature, and high overpotential). The concept, which originates from unique electron penetration through the 2D crystal layer from the encapsulated metals to promote a catalytic reaction on the outermost surface of the 2D crystal, has been widely applied in a variety of reactions under harsh conditions. It has been vividly described as “chainmail for catalyst.” Herein, recent progress concerning this chainmail catalyst is reviewed, particularly focusing on the structural design and control with the associated electronic properties of such heterostructure catalysts, and also on their extensive applications in fuel cells, water splitting, CO₂ conversion, solar cells, metal–air batteries, and heterogeneous catalysis. In addition, the current challenges that are faced in fundamental research and industrial application, and future opportunities for these fantastic catalytic materials are discussed.     

Highly Efficient and Stable Water‐Oxidation Electrocatalysis with a Very Low Overpotential using FeNiP Substitutional‐Solid‐Solution Nanoplate Arrays

The development of efficient water‐oxidation electrocatalysts based on inexpensive and earth‐abundant materials is significant to enable water splitting as a future renewable energy source. Herein, the synthesis of novel FeNiP solid‐solution nanoplate (FeNiP‐NP) arrays and their use as an active catalyst for high‐performance water‐oxidation catalysis are reported. The as‐prepared FeNiP‐NP catalyst on a 3D nickel foam substrate exhibits excellent electrochemical performance with a very low overpotential of only 180 mV to reach a current density of 10 mA cm^?2 and an onset overpotential of 120 mV in 1.0 m KOH for the oxygen evolution reaction (OER). The slope of the Tafel plot is as low as 76.0 mV dec^?1. Furthermore, the long‐term electrochemical stability of the FeNiP‐NP electrode is investigated by cyclic voltammetry (CV) at 1.10–1.55 V versus reversible hydrogen electrode (RHE), demonstrating very stable performance with negligible loss in activity after 1000 CV cycles. This present FeNiP‐NP solid solution is thought to represent the best OER catalytic activity among the non‐noble metal catalysts reported so far.     

Strongly Coupled 3D Hybrids of N‐doped Porous Carbon Nanosheet/CoNi Alloy‐Encapsulated Carbon Nanotubes for Enhanced Electrocatalysis

A novel 3D nanoarchitecture comprising in situ‐formed N‐doped CoNi alloy‐encapsulated carbon nanotubes (CoNi‐NCNTs) grown on N‐doped porous carbon nanosheets (NPCNs) is designed and constructed for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). When evaluated as an electrocatalyst for ORR, the hybrid shows efficient catalytic activity, high selectivity, superior durability, and strong tolerance against methanol crossover compared with the commercial Pt/C catalyst. Such good oxygen reduction reaction performance is comparable to most of the previously reported results and the synergistic effect is found to boost the catalytic performance. Moreover, the constructed hybrid exhibits an excellent ORR activity with a current density of 10 mA cm⁻² at 1.59 V and an onset potential of 1.57 V, even beyond the state‐of‐the‐art Ir/C catalyst in alkaline media. The enhancement in electrochemical performance can be attributed to the unique morphology and defect structures, high porosity, good conductive networks, and strongly interacting CoNi‐NCNT and NPCN in the hybrid. These results suggest the possibility for the development of effective nanocarbon electrocatalysts to replace commercial noble metal catalysts for direct use in fuel cells and water splitting devices.     

Engineering the pH‐Responsive Catalytic Behavior of AuNPs by DNA

Noble metal nanoparticles have attracted much interest in the heterogeneous catalysis. Particularly, efficient manipulation of the responsive catalytic properties of the metal nanoparticles is an interesting topic. In this work, a simple and efficient strategy is developed to regulate the pH‐responsive catalytic activities of glucose oxidase (GOx)‐mimicking gold nanoparticles (AuNPs). Four DNA strands (regulating strands) that differ slightly in sequences are used to interact non‐covalently with citrate‐capped AuNPs, resulting in markedly distinct pH‐dependent catalytic behavior of AuNPs. This is ascribed to the characteristic pH‐induced conformational change of the DNA strands that leads to the different adsorption capability to the NPs surface, as demonstrated by pH‐CD profiles of the respective DNA molecules. The pH‐dependent catalysis of AuNPs is also encoded with structural information of the double‐stranded DNA (including regulating strands and their complementary strands) that has conformation resistant or responsive to pH change. As a result, the catalysis can be programmed into an AND gate, a XNOR gate or a NOT gate, using pH and complementary strand as the inputs, the nanoparticle activity as the output and the regulating strands as the programs. This work can be expanded by engineering the catalytic behavior of noble metal nanoparticles to respond smartly to a variety of environmental stimuli, such as metal ions or light wavelengths. These results may provide insight into understanding ligand‐regulated nanometallic catalysis.     

A Simple and Effective Principle for a Rational Design of Heterogeneous Catalysts for Dehydrogenation of Formic Acid

Efficient and selective dehydrogenation of formic acid is a key challenge for a fuel‐cell‐based hydrogen economy. Though the development of heterogeneous catalysts has received much progress, their catalytic activity remains insufficient. Moreover, the design principle of such catalysts are still unclear. Here, experimental and theoretical studies on a series of mono‐/bi‐metallic nanoparticles supported on a NH₂‐N‐rGO substrate are combined for formic acid dehydrogenation where the surface energy of a metal is taken as a relevant indicator for the adsorption ability of the catalyst for guiding catalyst design. The AuPd/NH₂‐N‐rGO catalyst shows record catalytic activity by reducing the energy barrier of rate controlling steps of formate adsorption and hydrogen desorption. The obtained excellent results both in experiments and simulations could be extended to other important systems, providing a general guideline to design more efficient catalysts.     

Structurally Deformed MoS2 for Electrochemically Stable,Thermally Resistant,and Highly Efficient Hydrogen Evolution Reaction

The emerging molybdenum disulfide (MoS₂) offers intriguing possibilities for realizing a transformative new catalyst for driving the hydrogen evolution reaction (HER). However, the trade‐off between catalytic activity and long‐term stability represents a formidable challenge and has not been extensively addressed. This study reports that metastable and temperature‐sensitive chemically exfoliated MoS₂ (ce‐MoS₂) can be made into electrochemically stable (5000 cycles), and thermally robust (300 °C) while maintaining synthetic scalability and excellent catalytic activity through physical‐transformation into 3D structurally deformed nanostructures. The dimensional transition enabled by a high throughput electrohydrodynamic process provides highly accessible, and electrochemically active surface area and facilitates efficient transport across various interfaces. Meanwhile, the hierarchically strained morphology is found to improve electronic coupling between active sites and current collecting substrates without the need for selective engineering the electronically heterogeneous interfaces. Specifically, the synergistic combination of high strain load stemmed from capillarity‐induced‐self‐crumpling and sulfur (S) vacancies intrinsic to chemical exfoliation enables simultaneous modulation of active site density and intrinsic HER activity regardless of continuous operation or elevated temperature. These results provide new insights into how catalytic activity, electrochemical‐, and thermal stability can be concurrently enhanced through the physical transformation that is reminiscent of nature, in which properties of biological materials emerge from evolved dimensional transitions.     

Highly Efficient Photocatalytic Hydrogen Evolution by ReS2 via a Two‐Electron Catalytic Reaction

Highly efficient photocatalytic hydrogen evolution (PHE) is highly desirable for addressing the global energy crisis and environmental problems. Although much attention has been given to electron–hole separation, ridding photocatalysts of poor efficiency remains challenging. Here, a two‐electron catalytic reaction is developed by utilizing the distinct trion behavior of ReS₂ and the efficient reduction of two H⁺ (2H⁺ + 2e^? → H₂) is realized. Due to the monolayer‐like structure of the catalyst, the free electrons in ReS₂ can be captured by the tightly bound excitons to form trions consisting of two electrons and one hole. These trions can migrate to the surface and participate in the two‐electron reaction at the abundant active sites. As expected, such a two‐electron catalytic reaction endows ReS₂ with a PHE rate of 13 mmol g^?1 h^?1 under visible light irradiation. Meanwhile, this reaction allows the typically poor PHE efficiency of pure transition metal dichalcogenides to be overcome. The proposed two‐electron catalytic reaction provides a new approach to the design of photocatalysts for PHE.     

Stable and recyclable Pd catalyst supported on modified silica hollow microspheres with macroporous shells for enhanced catalytic hydrogenation of NBR

In this work, a stable and recyclable Pd catalyst supported on N-containing silane coupling agent modified silica hollow microspheres with macroporous shells (Pd/N-SHMs) was successfully prepared and used for the selective hydrogenation of nitrile-butadiene rubber (NBR) with enhanced catalytic performance. The results showed that Pd/N-SHMs possessed small-sized and well-dispersed Pd nanoparticles (NPs) and the macroporous shells were beneficial for the diffusion of macromolecular NBR, and thus with such a catalyst, the reaction could occur under mild conditions and high hydrogenation degree (96.6%) with 100% selectivity to C=C was obtained. The prepared catalyst could be easily recycled and reused with a high efficiency. More importantly, because of the strong coordination between Pd and diamine ligands, Pd NPs could be anchored steadily over the support and only 5.0 ppm Pd residues was detected in products. This reaction was considered as pseudo-first order at high H₂ pressures, and the reaction activation energy was calculated to be as low as 18.1 kJ/mol. Our contribution is to provide an efficient and recyclable supported Pd catalyst, which may promote the development of heterogeneous catalytic systems for unsaturated macromolecular hydrogenation.     

Tuning Surface Structure of 3D Nanoporous Gold by Surfactant‐Free Electrochemical Potential Cycling

3D dealloyed nanoporous metals have emerged as a new class of catalysts for various chemical and electrochemical reactions. Similar to other heterogeneous catalysts, the surface atomic structure of the nanoporous metal catalysts plays a crucial role in catalytic activity and selectivity. Through surfactant‐assisted bottom‐up synthesis, the surface‐structure modification has been successfully realized in low‐dimensional particulate catalysts. However, the surface modification by top‐down dealloying has not been well explored for nanoporous metal catalysts. Here, a surfactant‐free approach to tailor the surface structure of nanoporous gold by surface relaxation via electrochemical redox cycling is reported. By controlling the scan rates, nanoporous gold with abundant {111} facets or {100} facets can be designed and fabricated with dramatically improved electrocatalysis toward the ethanol oxidation reaction.     

Atomic Iridium Incorporated in Cobalt Hydroxide for Efficient Oxygen Evolution Catalysis in Neutral Electrolyte

Developing highly efficient catalysts for oxygen evolution reaction (OER) in neutral media is extremely crucial for microbial electrolysis cells and electrochemical CO₂ reduction. Herein, a facile one‐step approach is developed to synthesize a new type of well‐dispersed iridium (Ir) incorporated cobalt‐based hydroxide nanosheets (nominated as CoIr) for OER. The Ir species as clusters and single atoms are incorporated into the defect‐rich hydroxide nanosheets through the formation of rich Co–Ir species, as revealed by systematic synchrotron radiation based X‐ray spectroscopic characterizations combining with high‐angle annular dark‐field scanning transmission electron microscopy measurement. The optimized CoIr with 9.7 wt% Ir content displays highly efficient OER catalytic performance with an overpotential of 373 mV to achieve the current density of 10 mA cm^?2 in 1.0 m phosphate buffer solution, significantly outperforming the commercial IrO₂ catalysts. Further characterizations toward the catalyst after undergoing OER process indicate that unique Co oxyhydroxide and high valence Ir species with low‐coordination structure are formed due to the high oxidation potentials, which authentically contributes to superior OER performance. This work not only provides a state‐of‐the‐art OER catalyst in neutral media but also unravels the root of the excellent performance based on efficient structural identifications.     

Catalytic hydrogenation of various organic substrates using a reusable polymer-anchored palladium(II) complex

A stable, reusable, and highly active catalyst for liquid phase hydrogenation reaction has been developed by reacting poly(3,6-diamino N-vinylcarbazole) with benzaldehyde to get polymer-anchored Schiff base which was then reacted with bis(benzonitrile)palladium(II)chloride [Pd(PhCN)₂Cl₂] to get the polymer-anchored complex. The complex was characterized by using scanning electron microscope (SEM), thermogravimetric analysis (TGA), elemental analysis, atomic absorption spectroscopy (AAS), and spectrometric methods like diffuse reflectance spectra of solid (DRS) and Fourier transform infrared spectroscopy (FTIR). The catalytic performance of this catalyst was investigated in hydrogenation of various organic substrates under high-pressure condition. The results showed that the catalyst were highly efficient for hydrogenation reaction and gave excellent yields of products. At the same time, the catalyst was very stable and could be reused for more than five times without noticeable loss of its catalytic activity.     

Role of MoOx Surficial Modification in Enhancing the OER Performance of Ru–Pyrochlore

Pyrochlore ruthenate (Y₂Ru₂O_7–δ) is highlighted as a promising oxygen evolution reaction (OER) catalyst for water splitting in polymer electrolyte membrane electrolyzers. However, an efficient electronic modulation strategy for Y₂Ru₂O_7–δ is required to overcome its electrochemical inertness. Herein, a surface manipulation strategy involving implanting MoO_x moieties on nano Y₂Ru₂O_7–δ (Mo–YRO) using wet chemical peroxone method is demonstrated. In contrast to electronic structure regulation by intramolecular charge transfer (i.e., substitutional strategies), the heterogeneous Mo−O−Ru micro-interfaces facilitate efficient intermolecular electron transfer from [RuO₆] to MoO_x. This eliminates the bandgap by inducing Ru 4d delocalization and band alignment rearrangement. The MoO_x modifiers also alleviate distortion of [RuO₆] by shortening Ru−O bond and enlarging Ru−O−Ru bond angle. This electronic and geometric structure tailoring enhances the OER performance, showing a small overpotential of 240 mV at 10 mA cm⁻². Moreover, the electron-accepting MoO_x moieties provide more electronegative surfaces, which serve as a protective “fence” to inhibit the dissolution of metal ions, thereby stabilizing the electrochemical activity. This study offers fresh insights into the design of new-based pyrochlore electrocatalysts, and also highlights the versatility of surface engineering as a way of optimizing electronic structure and catalytic performance of other related materials.