Primary Active Site Research Articles

Hydrogen Spillover‐Promoted Hydrogen Evolution onto Copper

AbstractCurrently, green hydrogen harvesting from electrochemical water splitting is overly reliant on noble metals with high catalytic activity but low natural abundance and high cost. As one of potential earth‐abundant alternatives, copper, however, displays a poor hydrogen evolving capability, mainly due to inherently a weak hydrogen binding energy (HBE). It poses a substantial restriction to metallic Cu alone serving as primary active sites for high‐performance hydrogen evolution. Thanks to the presence of hydrogen spillover that was often overlooked during the electrocatalysis, the hydrogen evolution in a nonacidic electrolyte can be accelerated by the recombination desorption of adsorbed hydrogen over Cu with a weak HBE. Here, we concisely highlighted this promotion effect of secondary active Cu on electrocatalytic hydrogen evolution and eagerly expected to extend hydrogen spillover effects to the advance of multi‐site electrocatalytic systems.

Surface oxidation promotes the flotation of ilmenite: a critical review

Due to its high efficiency, ease of operation, and superior selectivity, flotation separation has emerged as a promising technique for the extraction of ilmenite from natural resources. In light of the solution chemistry of ilmenite, it is widely accepted that ferrous ions and ferrous hydroxy compounds serve as the primary active sites for collector adsorption across a broad range of slurry pH values. The commonly used collectors like sodium oleate and hydroxamic acid are capable of chemical bonding with Fe2+ to form complexes and then enhance the floatability of ilmenite. However, Fe3+ ions perform a higher affinity to both collectors rather than Fe2+, the formed stronger complexes are advantageous for enhancing the hydrophobicity of ilmenite and increasing the probability for air bubble attachment, resulting in an improved ilmenite flotation recovery. Consequently, how to maximize the conversion efficiency of Fe2+ to Fe3+ and provide additional Fe3+ active sites on ilmenite surface for collector attachment have become the hot spot. Herein, this review aims to firstly analyze the crystal structure and solution chemistry of ilmenite and then provide a concise summary of recent advances in different oxidation technologies for promoting the conversion of Fe2+ to Fe3+, including hydroxyl radicals oxidation, direct chemical oxidation, and thermal oxidation, and the in-depth activation mechanisms are well illustrated. Also, current challenges and perspectives in this field are discussed. This review would benefit the development of next-generation flotation techniques for earth-abundant titanium resources.

Surface bonding of MN4 macrocyclic metal complexes with pyridine-functionalized multi-walled carbon nanotubes for non-aqueous Li-O2 batteries

It is essential to develop bifunctional catalysts with high activity and stability for reversible oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) in lithium-oxygen (Li-O2) batteries. In this work, pyridine (Py) functionalized multi-walled carbon nanotubes (MWCNTs) were prepared to immobilize various solid MN4 macrocyclic metal complexes (MN4-MC) as cathode electrocatalysts for Li-O2 batteries. Three types of MN4-MC molecules, including iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc) and iron protoporphyrin IX (Heme) were examined to evaluate the influence of central metal atoms and ligand substituents found in MN4-MC molecules on the electrocatalytic performance of the study samples. The order of the ORR/OER catalytic activity of the bifunctional catalysts is FePc > Heme > CoPc. The central metal atom in FePc molecule has the highest occupied molecular orbital (HOMO) energy than the corresponding metal atoms in CoPc and Heme molecules. This made the molecule to have better dioxygen-binding ability and higher catalytic activity in the ORR process; it also made it to easily lose electrons that were oxidized in the OER process. This study proposed a simplified scheme of the electrode surface route to assist in understanding the diverse ORR/OER performances of MN4-MC. It is discovered that the positive core of the MN5 coordination sphere in MN4-MC/Py/MWCNTs composite is the primary active site that can influence the formation of MN5···O2* and MN5-LOOLi cluster in the ORR process. The interfacial electron could be easily delivered between MWCNTs and MN5 active site through the Py bridge. This facilitated the formation and decomposition of MN5-LOOLi species during the ORRs/OERs, leading to the enhancement of its catalytic performance. This work provides a new insight into the effects of the molecular structure and organization of MN4-MC on the catalytic activity of O2 electrodes in Li-O2 batteries.

Porous edge confinement: High carrier potential and low activation energy barrier synergistically boosting the efficiency of selective photocatalytic CO2 conversion

Catalysts which allow directional transfer of photogenerated electrons to catalytic sites are crucial to efficient photocatalytic CO2 reduction. Herein, 2D BiOCl porous nanosheets (BOC-PNS) are prepared by triblock polymer (F127) assisted mechanical ball milling. The main exposed plane is (001) on the BOC-PNS surface and the porous structure increases the edge (110) facet. The (001)/(110) heterojunction enhances directional migration and separation of photogenerated carriers. In situ Raman scattering, in situ Fourier transform infrared spectroscopy, 3D FDTD simulation and theoretical calculations reveal that the BOC (001) plane is enriched with directionally migrating photogenerated electrons and provides the primary active sites to bridge adsorption-activated CO2 molecules consequently producing a smaller energy barrier for the intermediate product of *COOH. Weak CO adsorption on the BOC (001) plane further promotes CO2 reduction. Upon exposure to simulated sunlight, the CO yield of BOC-PNS is enhanced by the rich edge confinement effect reaching 28.2 μmol g−1 h−1, which is 2.1 and 2.8 times that of the BOC nanosheets (13.5 μmol g−1 h−1) and nanoplates (9.9 μmol g−1 h−1), respectively.

Synergistic Porosity and Charge Effects in a Supramolecular Porphyrin Cage Promote Efficient Photocatalytic CO2 Reduction.

We present a supramolecular approach to catalyzing photochemical CO2 reduction through second-sphere porosity and charge effects. An iron porphyrin box (PB) bearing 24 cationic groups, FePB-2(P), was made via post-synthetic modification of an alkyne-functionalized supramolecular synthon. FePB-2(P) promotes the photochemical CO2 reduction reaction (CO2 RR) with 97 % selectivity for CO product, achieving turnover numbers (TON) exceeding 7000 and initial turnover frequencies (TOFmax ) reaching 1400 min-1 . The cooperativity between porosity and charge results in a 41-fold increase in activity relative to the parent Fe tetraphenylporphyrin (FeTPP) catalyst, which is far greater than analogs that augment catalysis through porosity (FePB-3(N), 4-fold increase) or charge (Fe p-tetramethylanilinium porphyrin (Fe-p-TMA), 6-fold increase) alone. This work establishes that synergistic pendants in the secondary coordination sphere can be leveraged as a design element to augment catalysis at primary active sites within confined spaces.

Synergistic Porosity and Charge Effects in a Supramolecular Porphyrin Cage Promote Efficient Photocatalytic CO2 Reduction**

AbstractWe present a supramolecular approach to catalyzing photochemical CO2 reduction through second‐sphere porosity and charge effects. An iron porphyrin box (PB) bearing 24 cationic groups, FePB‐2(P), was made via post‐synthetic modification of an alkyne‐functionalized supramolecular synthon. FePB‐2(P) promotes the photochemical CO2 reduction reaction (CO2RR) with 97 % selectivity for CO product, achieving turnover numbers (TON) exceeding 7000 and initial turnover frequencies (TOFmax) reaching 1400 min−1. The cooperativity between porosity and charge results in a 41‐fold increase in activity relative to the parent Fe tetraphenylporphyrin (FeTPP) catalyst, which is far greater than analogs that augment catalysis through porosity (FePB‐3(N), 4‐fold increase) or charge (Fe p‐tetramethylanilinium porphyrin (Fe‐p‐TMA), 6‐fold increase) alone. This work establishes that synergistic pendants in the secondary coordination sphere can be leveraged as a design element to augment catalysis at primary active sites within confined spaces.

Origin of Ammonia Selective Oxidation Activity of SmMn2O5 Mullite: A First-Principles-Based Microkinetic Study.

Based on first-principles calculations and microkinetic analysis, the reaction routes and origin of the activity of SmMn2O5 mullite for the selective catalytic oxidation of ammonia (NH3-SCO) are systematically investigated on three low-index surfaces under experimentally operating conditions. Key influencing factors and contributions of different iconic intermediate species (NH*, N2H4*, and HNO*) to the overall reaction process have been identified. In detail, Mn4+ serves as the primary active site for NH3 adsorption, while lattice oxygen participates in the dehydrogenation of NH3 on (010)4+ and (001)4+ surfaces. Furthermore, the (010)4+ surface shows both the best activity and the highest N2 selectivity at low temperatures via the synergy effect of exposed Mn-Mn dimers and the most labile O2 atoms. We further evaluate the potential catalytic performances of six A-site doped (010)4+ facets, among which La, Pr, and Nd dopings are predicted to possess better catalytic performances. Our study provides deep insights into the microscope reaction mechanisms and provides the specific optimization strategy for NH3-SCO on mullite oxides.

In situ monitoring of dynamic behavior of La-doped CuCl2/γ-Al2O3 catalyst in ethylene oxychlorination

The oxidation state of Cu species in ethylene oxychlorination is strongly correlated with catalytic performance. CuCl2 and CuCl have been identified as the primary active sites in the reduction and oxidation step, respectively, according to a redox-type mechanism. The distribution of the active sites is governed by the kinetic equilibrium of the reduction, oxidation, and hydrochlorination rates at steady-state. Herein, in situ X-ray absorption spectroscopy (XAS) and operando ultraviolet–visible and near-infrared spectroscopy (UV–vis-NIR) were utilized to quantify the dynamic changes of the Cu active sites over the La-doped CuCl2/γ-Al2O3 in transient and steady-state experiments. A higher CuCl2 concentration plays a key role in dominating the higher activity, EDC selectivity, and stability. The in situ XAS result evidenced La was considered as a structural additive to increase the reducibility of the active CuCl2 and modify the catalytic performance instead of directly involving the reduction-oxidation cycle. A deeper understanding of the complex role of the active species and promoter in the CuCl2/γ-Al2O3 based-catalysts for ethylene oxychlorination was obtained.

Segmental Motion Adjustment of the Polycarbonate Electrolyte for Lithium-Metal Batteries.

Carbonyl oxygen atoms are the primary active sites to solvate Li salts that provide a migration site for Li ions conducting in a polycarbonate-based polymer electrolyte. We here exploit the conductivity of the polycarbonate electrolyte by tuning the segmental motion of the structural unit with carbonyl oxygen atoms, while its correlation to the mechanical and electrochemical stability of the electrolyte is also discussed. Two linear alkenyl carbonate monomers are designed by molecular engineering to combine methyl acrylate (MA) and the commonly used ethylene carbonate (EC), w/o dimethyl carbonate (DMC) in the structure. The integration of the DMC structural unit in the side chain of the in situ constructed polymer (p-MDE) releases the free motion of the terminal EC units, which leads to a lower glass-transition temperature and higher ionic conductivity. While pure polycarbonates are normally fragile with high Young's modulus, such a prolonged side chain also manipulates the flexibility of the polymer to provide a mechanical stable interface for Li-metal anode. Stable long-term cycling performance is achieved at room temperature for both LiFePO4 and LiCoO2 electrodes based on the p-MDE electrolyte incorporated with a solid plasticizer.

Selective Photocatalytic Transformation of Lignin to Aromatic Chemicals by Crystalline Carbon Nitride in Water–Acetonitrile Solutions

The photocatalytic conversion of lignin to aromatic compounds in aqueous solutions is a promising approach. We herein report a crystalline carbon nitride prepared by high-temperature thermal polymerization and alkali-metal molten salt treatment, which was then applied in the selective conversion of lignin to aromatic compounds. The results showed that the tri-s-tri-C3N4 presented a relatively high activity and selectivity for the conversion of lignin in aqueous solutions. In a 95% water-acetonitrile solution, it achieved a relatively high conversation rate of lignin, reaching 62.00%, and the selectivity of the C-C bond cleavage was high, at 86.8%. The characterization results obtained by TEM, UV-vis/DRS, PL, and transient photocurrent response showed that the ultra-high activity of tri-s-tri-C3N4 was mainly due to the improvements in crystallinity and light absorption. Mechanism studies showed that the dispersion of the catalyst and the combination of lignin and catalyst in aqueous solvents with different acetonitrile ratios were the main factors affecting lignin conversion. As the water content in the solutions increased, the primary active sites were converted from h+ to ·O2-. This study revealed the interactions between lignin, photocatalysts, and reaction solutions, providing a theoretical basis for the photocatalytic conversion of lignin in aqueous solutions.

(Digital Presentation) Iron-Based Electrode Structures for Ammonia Electrosynthesis Cells with Proton-Conducting Ceramic Electrolytes

Ammonia electrosynthesis is considered promising for the production of ammonia as an energy carrier, as the process could provide greater flexibility and compatibility to the fluctuations of renewable energy than the industrial Haber-Bosch process. One approach for enhancing the ammonia formation rate is the electrochemical promotion of catalysis (EPOC) [1], in which a non-faradaic acceleration of ammonia synthesis is observed; however, much of the mechanism remains unclear. Further mechanistic insight would aid in designing better electrode structures that are suited for efficient ammonia electrosynthesis. In this presentation, we explore the mechanism underlying the electrochemical promotion of ammonia synthesis, using electrochemical cells with iron-based cathodes on a proton-conducting BaCe0.9Y0.1O3 (BCY) electrolyte.Previously, our group reported that the ammonia formation rate of a cathodically polarized cell can be enhanced by adding H2 to the cathode gas feed (commonly pure N2) [2, 3]. Further kinetic and isotopic analysis using deuterium showed that the primary hydrogen source for the ammonia produced was the gaseous hydrogen feed, rather than the protons conducted via the electrolyte [4]. Cells with a porous pure Fe cathode resulted in higher ammonia formation rates than those with a porous 10 wt.% Fe-BCY cathode, suggesting that the pure Fe surfaces near the cathode-electrolyte interface, as opposed to the triple phase boundaries, are active for ammonia electrosynthesis [3]. However, the 10 wt.% Fe-BCY cathode, fabricated by the impregnation method, was thought to be limited by lack of Fe network formation needed for electron conduction.In this study, we fabricated a cermet cathode with the composition 56 wt.% Fe-BCY, aiming for Fe and BCY to form separate networks for electron and proton conduction, respectively. Electrochemical cells of the configurations Pt|BCY|Fe and Pt|BCY|Fe-BCY [Fig. 1a], with similar Fe mass (0.5 and 0.4 mg) were compared. Ammonia synthesis was conducted in a single-chamber reactor at 500-600˚C with a 50% H2/50% N2 feed. The gaseous ammonia produced was captured by bubbling into a dilute H2SO4 solution and quantified via high-performance liquid chromatography.Using the pure Fe electrode, an ammonia formation rate of 1.3 × 10-8 mol s-1 cm-2 (26 mmol gFe -1 h-1) was obtained at 600˚C and -1 V [Fig. 1b]. This corresponds to an almost 5-fold increase in ammonia formation compared to the catalytic reaction at 0 V. In contrast, a lower ammonia formation rate of 7.0 × 10-9 mol s-1 cm-2 (17 mmol gFe -1 h-1) was obtained using the Fe-BCY electrode at the same conditions. Despite the cermet electrode having a slightly higher current density, and despite the comparable iron loading on the two cells, the pure Fe cell still resulted in a faster ammonia formation rate per electrode area and per iron mass. As the cermet electrode is expected to have a significantly longer triple phase boundary length, from the comparison of these two electrochemical cells, the triple phase boundaries do not appear to be the primary active sites. We further analyze the roles of the bulk Fe surfaces and the Fe/BCY triple phase boundaries, by examining the effect of the electrode thickness and by post-experiment cross-sectional electron microscopy approaches.AcknowledgementsThis work was supported by JSPS KAKENHI Grant Number JP21H04938.

Catalytic Dehydrogenation of Ethane over Mn Oxide Supported on Zeolite Chabazite

AbstractA new class of Mn‐containing zeolites prepared by incipient wetness impregnation (IWI) have been found to catalyze the ethane dehydrogenation reaction with high selectivity (98 %+). Preparation by IWI leads to the formation of Mn2O3 nanoparticles on the external surface of the zeolite crystals and herein is shown that the primary active sites for the reaction are located on the surface of these particles. Propane dehydrogenation is also successfully catalyzed by this catalyst. Other Mn‐zeolites (MFI and BEA) also have high reactivity and selectivity towards light alkane dehydrogenation.

Ultrafast self-assembly Fe2O3 nanoparticles confined in carbon layers toward robust heterogeneous electro-Fenton reaction

Heterogeneous electro-Fenton (EF) is a promising advanced oxidation process for refractory wastewater treatment. However, typical calcination or hydrothermal method for heterogeneous EF cathode fabrication is time-consuming, energy-consuming, or harmful to the environment. High-temperature shock (HTS) technique is a novel and rapid material synthesis method with the advantages of low-cost, eco-friendly. In this study, the electrodes named Fe2O3@C/carbon cloth (Fe2O3@C/CC), were synthesized by HTS for the first time within an extremely short time (∼5 s). The Fe2O3 nanoparticles with an average diameter of 61.90 ± 15.09 nm are uniformly dispersed on carbon cloth (CC) with the confinement and protection of the carbon layers. The as-prepared Fe2O3@C/CC cathode exhibited excellent electrocatalytic properties in the EF system. The removal efficiency of methylisothiazolinone (MIT) could reach 90.60 ± 1.70% in 40 min at a low current density of 1.11 mA cm−2 under the oxidation of the hydroxyl radical. In addition, the degradation pathways of MIT were further studied. According to the results of theoretical calculation, the –S–N– bond is the primary active site attacked during MIT degradation process. Therefore, heterocyclic loop opening is the main pathway of MIT degradation. HTS is an ultrafast and convenient potential technique compared with other cathode synthesis methods.

Strongly coupled Fe/N co-doped graphitic carbon nanosheets/carbon nanotubes for rapid degradation of organic pollutants via peroxymonosulfate activation: Performance, mechanism and degradation pathways

Exploration of magnetic carbon-based catalysts with high catalytic activity and recyclability is essential for peroxymonosulfate (PMS) activation. A feasible method for the synthesis of Fe/N co-doped graphitic carbon nanosheets/carbon nanotubes (Fe/N-GCNS@CNTs) using a one-step pyrolysis procedure was proposed in this paper. The Fe/N-GCNS@CNTs possessed an interconnected carbon framework composed of GCNS and CNTs. The carbon framework could not only improve the mass transfer efficiency and mineralization capability of Fe/N-GCNS@CNTs, but it could also protect the Fe nanoparticles against metal leaching. The as-obtained Fe/N-GCNS@CNTs-800 demonstrated excellent performance for PMS activation to degrade organic pollutants. 100% of 50 mg/L rhodamine B (RhB) was rapidly degraded in 5 min when PMS (0.5 mM) and 50 mg/L Fe/N-GCNS@CNTs-800 were added. Meanwhile, the Fe/N-GCNS@CNTs-800/PMS system possessed a broad efficient pH range (3.0–9.0), good anti-interference capacity (anions and HA), and low iron leaching concentration (138 µg/L). Fe/N-GCNS@CNTs-800 could be magnetically separated from the suspension very easily because of its good saturation magnetization (11.25 emu/g). In addition, quenching experiments, electron spin resonance (ESR) measurements, and electrochemical assessments demonstrated that radical (.OH and SO4⋅−) and non-radical (1O2 and electron transfer) processes cooperated to contribute to the rapid RhB degradation. XPS analysis revealed that the primary catalytic active sites of Fe/N-GCNS@CNTs-800 were pyridinic N, C=O groups, and Fe/Fe3C species. LC-MS analyses were used to propose possible RhB degradation pathways. This study provided an intrinsic mechanism of PMS activation by magnetic carbon-based catalysts for the removal of organic pollutants in water treatment.

Advances in understanding the active sites of Cu catalysts in glycerol hydrogenolysis to 1,2-propanediol

ABSTRACT Compared with fossil-dependent process, glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) is a green sustainable route with much advantage. The commercial scale of this reaction has been achieved, and catalysts with high efficiency are continuously developed. Cu-based catalysts are considered as the most selective catalysts for 1,2-PDO production, which are widely investigated up to now. Understanding the structure-activity relationship can help the design of new catalytic materials with improved activity, selectivity and stability. In this review, the roles of various active structures on Cu catalysts are summarized. We introduce firstly the pioneering works, showing that Cu species are the primary active sites which can catalyze both the glycerol dehydration and C = O bond hydrogenation steps. Then, we summarize various viewpoints about the structure-sensitive effect of Cu in the reaction. The functions of support and promoter are subsequently discussed in detail, and the roles of the secondary metal site are further overviewed. After that, we propose critical factors that should be considered when investigating the Cu structure sensitive effect, and summarize three general roles of support, promoter and secondary metal. Further important research directions for Cu catalysts in glycerol hydrogenolysis are also outlined.

Synthesis of polydopamine modified MgAl-LDH for high efficient Cr(VI) removal from wastewater

A highly efficient absorbent was developed in this study by modifying polydopamine film on Mg–Al layered double hydroxide (PDA/MgAl-LDH) to remove Cr(VI) from wastewater. The characterization results showed that the polydopamine film was successfully coated on the MgAl-LDH surface. The preparation ratio, pH, and adsorbent dosage influencing absorption by PDA/MgAl-LDH were systematically investigated. The absorption capacity of Cr(VI) by PDA/MgAl-LDH was 87 mg/g. The equilibrium adsorption isotherm of PDA/MgAl-LDH was in good agreement with that of the Langmuir model. Therefore, the pseudo-second-order kinetic model is suitable for describing adsorption kinetics. The interaction between PDA and Cr(VI) and Cr(III) was investigated using density generalized function theory (DFT), which demonstrated that the PDA amino group could provide electrons for Cr(VI) reduction. Hydrogen and covalent bonding were dominant during the chemisorption process of PDA absorbing Cr(VI), the nitrogen of 5,6-dihydroxyindole was the primary active site for absorbing Cr(III), and electrostatic attraction was mainly responsible for Cr(III) absorption. Therefore, PDA/MgAl-LDH has the potential to adsorb and remove Cr(VI) from wastewater.

Multifunctional Charge and Hydrogen‐Bond Effects of Second‐Sphere Imidazolium Pendants Promote Capture and Electrochemical Reduction of CO2in Water Catalyzed by Iron Porphyrins**

AbstractMicroenvironments tailored by multifunctional secondary coordination sphere groups can enhance catalytic performance at primary metal active sites in natural systems. Here, we capture this biological concept in synthetic systems by developing a family of iron porphyrins decorated with imidazolium (im) pendants for the electrochemical CO2reduction reaction (CO2RR), which promotes multiple synergistic effects to enhance CO2RR and enables the disentangling of second‐sphere contributions that stem from each type of interaction.Fe‐ortho‐im(H), which poises imidazolium units featuring both positive charge and hydrogen‐bond capabilities proximal to the active iron center, increases CO2binding affinity by 25‐fold and CO2RR activity by 2000‐fold relative to the parent Fe tetraphenylporphyrin (Fe‐TPP). Comparison with monofunctional analogs reveals that through‐space charge effects have a greater impact on catalytic CO2RR performance compared to hydrogen bonding in this context.

Multifunctional Charge and Hydrogen-Bond Effects of Second-Sphere Imidazolium Pendants Promote Capture and Electrochemical Reduction of CO2 in Water Catalyzed by Iron Porphyrins.

Microenvironments tailored by multifunctional secondary coordination sphere groups can enhance catalytic performance at primary metal active sites in natural systems. Here, we capture this biological concept in synthetic systems by developing a family of iron porphyrins decorated with imidazolium (im) pendants for the electrochemical CO2 reduction reaction (CO2 RR), which promotes multiple synergistic effects to enhance CO2 RR and enables the disentangling of second-sphere contributions that stem from each type of interaction. Fe-ortho-im(H), which poises imidazolium units featuring both positive charge and hydrogen-bond capabilities proximal to the active iron center, increases CO2 binding affinity by 25-fold and CO2 RR activity by 2000-fold relative to the parent Fe tetraphenylporphyrin (Fe-TPP). Comparison with monofunctional analogs reveals that through-space charge effects have a greater impact on catalytic CO2 RR performance compared to hydrogen bonding in this context.

A New Supramolecular Tetraruthenated Cobalt (II) Porphyrazine Displaying Outstanding Electrocatalytical Performance in Oxygen Evolution Reaction.

A new supramolecular electrocatalyst for Oxygen Evolution Reaction (OER) was synthesized from a central multibridging cobalt tetrapyridylporphyrazine (CoTPyPz) species by attaching four [Ru(bpy)2Cl]+ groups. Both CoTPyPz and the tetraruthenated cobalt porphyrazine species, TRuCoTPyPz, form very homogenous molecular films just by dropcasting their methanol solutions onto GCE electrodes. Such films exhibited low overpotentials for O2 evolution, e.g., 560 e 340 mV, respectively, displaying high stability, typically exceeding 15 h. The kinetic parameters obtained from the Tafel plots showed that the peripheral complexes are very important for the electrocatalytic activity. Hyperspectral Raman images taken along the electrochemical process demonstrated that the cobalt center is the primary active catalyst site, but its performance is enhanced by the ruthenium complexes, which act as electron-donating groups, in the supramolecular system.

Promoting Ex‐Solution from Metal–Organic‐Framework‐Mediated Oxide Scaffolds for Highly Active and Robust Catalysts (Adv. Mater. 27/2022)

Ex-Solution Catalysts In article number 2201109, WooChul Jung, Il-Doo Kim, and co-workers reconceptualize the ex-solution process with the design of a host oxide structure using a metal–organic framework as an oxide precursor. The critical challenges of ex-solution, which emerge through conventional synthesis methods, are addressed all at once through this strategy. The ex-solved nanoparticles promote oxygen chemisorption and function as primary active sites for acetone oxidation reactions in an example process, attaining record-breaking performance in acetone oxidation and acetone-detection reactions.