Catalytic Active Sites Research Articles

Identification of novel single nucleotide variants in the drug resistance mechanism of Mycobacterium tuberculosis isolates by whole-genome analysis

BackgroundTuberculosis (TB) represents a major global health challenge. Drug resistance in Mycobacterium tuberculosis (MTB) poses a substantial obstacle to effective TB treatment. Identifying genomic mutations in MTB isolates holds promise for unraveling the underlying mechanisms of drug resistance in this bacterium.MethodsIn this study, we investigated the roles of single nucleotide variants (SNVs) in MTB isolates resistant to four antibiotics (moxifloxacin, ofloxacin, amikacin, and capreomycin) through whole-genome analysis. We identified the drug-resistance-associated SNVs by comparing the genomes of MTB isolates with reference genomes using the MuMmer4 tool.ResultsWe observed a strikingly high proportion (94.2%) of MTB isolates resistant to ofloxacin, underscoring the current prevalence of drug resistance in MTB. An average of 3529 SNVs were detected in a single ofloxacin-resistant isolate, indicating a mutation rate of approximately 0.08% under the selective pressure of ofloxacin exposure. We identified a set of 60 SNVs associated with extensively drug-resistant tuberculosis (XDR-TB), among which 42 SNVs were non-synonymous mutations located in the coding regions of nine key genes (ctpI, desA3, mce1R, moeB1, ndhA, PE_PGRS4, PPE18, rpsA, secF). Protein structure modeling revealed that SNVs of three genes (PE_PGRS4, desA3, secF) are close to the critical catalytic active sites in the three-dimensional structure of the coding proteins.ConclusionThis comprehensive study elucidates novel resistance mechanisms in MTB against antibiotics, paving the way for future design and development of anti-tuberculosis drugs.

N-doped Ru/Mo2C-based electrocatalyst for outstanding and durable hydrogen evolution reaction with universal pH

The fabrication of Pt-free electrocatalysts with outstanding activity is crucial for reducing the overpotential of the hydrogen evolution reaction (HER) and advancing the next generation of energy technologies. This study introduced a scalable one-pot pyrolysis approach for fabricating N-doped Ru/Mo2C (MCNRx) for HER. The MCNR1 catalyst offered several advantages for electrocatalytic applications and beyond. The N-doped Ru/Mo2C prevented the agglomeration of Mo2C nanomaterials and improved their electronic conductivity. Moreover, the Ru metal was uniformly distributed, providing a large number of active catalytic sites, and the enhanced crystallinity and conductive surfaces generated from the trimesic acid create mass electron migration and facilitate the presence of active centers. The MCNR1 electrocatalyst, designed with the abovementioned advantages, had exceptional performance for HER across a broad pH range. For instance, it achieved a current density of 10 mA cm−2 with an overpotential of 35 mV in 1.0 M KOH, 44 mV in 0.5 M H2SO4, and 196 mV in 1.0 M phosphate-buffered saline (PBS). Furthermore, the electrocatalyst had exceptional long-term stability across all pH levels compared to Pt/C. The synthetic approach devised in this study can be employed for various cost-effective replacements for Pt-based electrocatalysts for HER.

Hexagonal boron nitride-doped carbon membrane as anode for the enhanced adsorption and electrochemical oxidation of phenol

An activated carbon membrane (ACM) doped with hexagonal boron nitride (h-BN) was fabricated by using activated carbon as the raw material and phenolic resin as the binder. The preparation process involves blending raw materials, ball milling, membrane pressing, and high-temperature carbonization. The conductive ACM was employed as an anode to constitute an electrochemical membrane reactor (EMR) for phenol removal. The effect of h-BN doping rate (0–5 wt%) on the properties of ACM was explored. Results showed that ACM1 (1 wt% h-BN) displayed a small pore size (20 nm), high porosity (41.6 %), large specific surface area (446.8 m2/g), and strong mechanical strength (15.4 MPa) compared to the pristine ACM0. The oxygen precipitation potential of ACM1 (2.11 V) was much higher than that of ACM0 (1.53 V), thus reducing oxygen generation at the anode in EMR for phenol degradation. The phenol removal rate of phenol obtained from EMR with ACM1 as the anode at 1.5 V was up to 95.6 %, which was much higher than that for ACM0 (39.3 %). Density functional theory (DFT) calculations and experimental results confirmed that h-BN-doping enhanced the adsorption active sites, and adsorption energy, leading to the high performance of EMR for phenol removal. In addition, the equilibrium adsorption capacity of ACM1 (10.2 mg/g) was much higher than that of ACM0 (3.7 mg/g). The C atoms adjacent to pyridine N in ACM1 were identified as the adsorption and active catalytic sites by X-ray photoelectron spectroscopy (XPS) and DFT calculations. Therefore, this study sheds light on the design and fabrication of conductive carbon membranes for enhanced performance in industrial wastewater treatment.

Enhancement of oxygen evolution reaction by in situ growth PMo12@ZIF-67 on MWCNTs via perylene bisimide-based dispersant

The combination of metal organic frameworks (MOFs) and multi-walled carbon nanotubes (MWCNTs) can significantly improve their electrochemical performance. However, in most cases, chemical pre-treatment of MWCNTs is inevitable, which may compromise the ideal performance of the final composites. Herein, via a noncovalent functionalization method, PMo12@ZIF-67 was in situ grown on the surfaces of MWCNTs with the assistance of a new dispersant containing two triethylenetetramine (TETA) segments. In order to enhance the coordination of Co metal ions with the surface of MWCNTs, phenolic hydroxyl groups were incorporated into the dispersant through reaction with gallic acid (GA). After annealing, homogeneous CNT/Co6Mo6C2/Co composites were obtained, and they showed excellent performance on oxygen evolution reaction (OER). At a current density of 10 mA cm−2, the lowest overpotential is 263 mV, of which the performance is superior to that achieved by other in situ growth methods. The uniform distribution of coordination sites and subsequent in situ growth of MOFs on MWCNTs improved the electrical conductivity of the derivatives, thereby enhanced the utilization of catalytic active sites. This study presents a novel approach for synthesizing carbon-doped electrocatalytic materials, which demonstrates significant potential in various electrochemical applications.

Electrochemical Restructuring Driven Catalytic Cycle of Bi-Based Heterojunctions for High-Performance Lithium-Sulfur Batteries.

Restructuring is an important phenomenon in catalytic reactions. Conversion-type materials with suitable redox potential may undergo in situ electrochemically driven restructurings and induce highly active catalytic sites in a working lithium-sulfur battery. Herein, driven by the electrochemical conversion reaction of BiVO4, a reversible catalytic cycle of Bi/amorphous Li3VO4 (a-Li3VO4) and Bi2S3/a-Li3VO4 heterojunctions is constructed, which targets the oxidation of Li2S and the conversion of polysulfide, respectively. The heterostructures and electrochemically driven size confinement provide abundant sites for shuttle restraining and sulfur conversion. Especially, the p-block Bi and Bi2S3 could dramatically reduce the conversion energy barriers of Li2S and polysulfide by virtue of the p-p orbital hybridization, promoting bidirectional reactions of the sulfur cathode. As a result, the corresponding sulfur cathode possesses a high reversible capacity of 7.5 mAh cm-2 after 120 cycles under a high sulfur loading of 10.3 mg cm-2 with a current density of 0.38 mA cm-2. This study furnishes a feasible scheme to obtain highly effective catalysts for bidirectional sulfur redox by utilizing the electrochemically induced restructuring.

CoFe2O4 nanosheets grown in situ on nickel nanowires for efficient hydrazine oxidation-boosted hydrogen production

The use of the hydrazine oxidation reaction (HzOR) to replace the oxygen evolution reaction (OER), which has a large thermodynamic barrier and a slow kinetic process, is a feasible way to achieve energy saving hydrogen production, but the construction of superior bifunctional catalysts is also challenging. Herein, an array (CoFe2O4@NNWs) of CoFe2O4 nanosheet grown in situ on nickel nanowires (NNWs) has been prepared and showed the excellent performance for hydrogen evolution reaction (HER) and HzOR under alkaline media, which require a lower potential of −91 mV (vs. RHE) for HzOR and 45 mV (vs. RHE) for HER at the current density (j, 10 mA cm−2). The overall hydrazine splitting (OHzS) electrolyzer requires cell voltages of 0.028 V (10 mA cm−2) and 1.227 V (1000 mA cm−2) by using electricity, wind, solar and thermal energies as power sources and had remarkable long-term stability. In addition, the potential of the OHzS is 1.67 V lower than that of OWS at the j of 10 mA cm−2. The excellent performance of CoFe2O4@NNWs is attributed to the fact that the heterojunction fromed by CoFe2O4 and NNWs effectively regulates the electron density of the sample, thereby improving the kinetics of H* adsorption and the N2H4 dehydrogenation, which can be confirmed by DFT. Second, the continuous electron transport channel provided by NNWs improves the electrical conductivity of the sample. In addition, the 2D CoFe2O4 nanosheets grown on NNWs not only expose more catalytic active sites, but also provide a fast channel for the diffusion of the electrolyte.

High-Entropy Lithium Niobate Nanocubes for Photocatalytic Water Splitting under Visible Light.

The vast compositional space available in high-entropy oxide semiconductors offers unique opportunities for electronic band structure engineering in an unprecedented large room. In this work, with wide band gap semiconductor lithium niobate (LiNbO3) as a model system, we show that the substitutional addition of high-entropy metal cation mixtures within the Nb sublattice can lead to the formation of a single-phase solid solution featuring a substantially narrowed band gap and intense broadband visible light absorption. The resulting high-entropy LiNbO3 [denoted as Li(HE)O3] crystallizes as well-faceted nanocubes; atomic-resolution imaging and elemental mapping via transmission electron microscopy unveil a distinct local chemical complexity and lattice distortion, characteristics of high-entropy stabilized solid solution phases. Because of the presence of high-entropy stabilized Co2+ dopants that serve as active catalytic sites, Li(HE)O3 nanocubes can accomplish the visible light-driven photocatalytic water splitting in an aqueous solution containing methanol as a sacrificial electron donor without the need of any additional co-catalysts.

Anion Structure Regulation of Cobalt Silicate Hydroxide Endowing Boosted Oxygen Evolution Reaction.

Transition metal silicates (TMSs) are attempted for the electrocatalyst of oxygen evolution reaction (OER) due to their special layered structure in recent years. However, defects such as low theoretical activity and conductivity limit their application. Researchers always prefer to composite TMSs with other functional materials to make up for their deficiency, but rarely focus on the effect of intrinsic structure adjustment on their catalytic activity, especially anion structure regulation. Herein, applying the method of interference hydrolysis and vacancy reserve, new silicate vacancies (anionic regulation) are introduced in cobalt silicate hydroxide (CoSi), named SV-CoSi, to enlarge the number and enhance the activity of catalytic sites. The overpotential of SV-CoSi declines to 301mV at 10mA cm-2 compared to 438mV of CoSi. Source of such improvement is verified to be not only the increase of active sites, but also the positive effect on the intrinsic activity due to the enhancement of cobalt-oxygen covalence with the variation of anion structure by density functional theory (DFT) method. This work demonstrates that the feasible intrinsic anion structure regulation can improve OER performance of TMSs and provides an effective idea for the development of non-noble metal catalyst for OER.

Stepwise structural evolution toward robust carboranealkynyl-protected copper nanocluster catalysts for nitrate electroreduction.

Atomically precise metal nanoclusters (NCs) are emerging as idealized model catalysts for imprecise metal nanoparticles to unveil their structure-activity relationship. However, the directional synthesis of robust metal NCs with accessible catalytic active sites remains a great challenge. In this work, we achieved bulky carboranealkynyl-protected copper NCs, the monomer Cu13·3PF6 and nido-carboranealkynyl bridged dimer Cu26·4PF6, with fair stability as well as accessible open metal sites step by step through external ligand shell modification and metal-core evolution. Both Cu13·3PF6 and Cu26·4PF6 demonstrate remarkable catalytic activity and selectivity in electrocatalytic nitrate (NO3-) reduction to NH3 reaction, with the dimer Cu26·4PF6 displaying superior performance. The mechanism of this catalytic reaction was elucidated through theoretical computations in conjunction with in situ FTIR spectra. This study not only provides strategies for accessing desired copper NC catalysts but also establishes a platform to uncover the structure-activity relationship of copper NCs.

A Volcano Correlation between Catalytic Activity for Sulfur Reduction Reaction and Fe Atom Count in Metal Center.

Sulfur reduction reaction (SRR) facilitates up to 16 electrons, which endows lithium-sulfur (Li-S) batteries with a high energy density that is twice that of typical Li-ion batteries. However, its sluggish reaction kinetics render batteries with only a low capacity and cycling life, thus remaining the main challenge to practical Li-S batteries, which require efficient electrocatalysts of balanced atom utilization and site-specific requirements toward highly efficient SRR, calling for an in-depth understanding of the atomic structural sensitivity for the catalytic active sites. Herein, we manipulated the number of Fe atoms in iron assemblies, ranging from single Fe atom to diatomic and triatomic Fe atom groupings, all embedded within a carbon matrix. This led to the revelation of a "volcano peak" correlation between SRR catalytic activity and the count of Fe atoms at the active sites. Utilizing operando X-ray absorption and X-ray diffraction spectroscopies, we observed that polysulfide adsorption-desorption and electrochemical conversion kinetics varied up and down with the incremental addition of even a single iron atom to the catalyst's metal center. Our results demonstrate that the metal center with exactly two iron atoms represents the optimal configuration, maximizing atom utility and adeptly handling the conversion of varied intermediate sulfur species, rendering the Li-S battery with a high areal capacity of 23.8 mAh cm-2 at a high sulfur loading of 21.8 mg cm-2. Our results illuminate the pivotal balance between atom utilization and site-specific requirements for optimal electrocatalytic performance in SRR and diverse electrocatalytic reactions.

Strukturelle Einblicke in die Terpencyclasedomänen Zweier Pilzlicher Sesterterpensyntasen und Enzymengineering zur Diversifizierung von Sesterterpenen

AbstractÜber die Strukturen und katalytischen Mechanismen von Sesterterpensynthasen (StTSs) ist wenig bekannt, was das strukturbasierte Engineering von StTSs zur Erweiterung der strukturellen Diversität von Sesterterpenen erheblich erschwert. Wir berichten hier über die Kristallstrukturen der Terpencyclisierungsdomänen (TC) von zwei pilzlichen StTSs: der Sesterfisherol‐Synthase (NfSS) und der Sesterbrasiliatrien‐Synthase (PbSS). Beide TC‐Strukturen enthalten Benzyltriethylammoniumchlorid (BTAC), Pyrophosphat (PPi) und Magnesiumionen (Mg2+), wodurch die katalytisch aktiven Zentren klar definiert sind. Eine Kombination aus Theorie und Experimenten, einschließlich der Modellierung carbokationischer Intermediate, ortsgerichteter Mutagenese und Isotopenmarkierungen, lieferte detaillierte Einblicke in die strukturellen Grundlagen der katalytischen Mechanismen. Strukturbasiertes Engineering von NfSS und PbSS führte zur Bildung von 20 Sesterterpenen, darunter 13 neue Verbindungen und vier Epimerpaare mit unterschiedlichen Konfigurationen an C18. Diese Ergebnisse erweitern die strukturelle Vielfalt von Sesterterpenen und liefern wichtige Erkenntnisse für die zukünftige Forschung im Bereich der synthetischen Biologie.

Structural Insights Into the Terpene Cyclization Domains of Two Fungal Sesterterpene Synthases and Enzymatic Engineering for Sesterterpene Diversification.

Little is known about the structures and catalytic mechanisms of sesterterpene synthases (StTSs), which greatly hinders the structure-based engineering of StTSs for structural diversity expansion of sesterterpenes. We here report on the crystal structures of the terpene cyclization (TC) domains of two fungal StTSs: sesterfisherol synthase (NfSS) and sesterbrasiliatriene synthase (PbSS). Both TC structures contain benzyltriethylammonium chloride (BTAC), pyrophosphate (PPi), and magnesium ions (Mg2+), clearly defining the catalytic active sites. A combination of theory and experiments including carbocationic intermediates modeling, site-directed mutagenesis, and isotope labeling provided detailed insights into the structural basis for their catalytic mechanisms. Structure-based engineering of NfSS and PbSS resulted in the formation of 20 sesterterpenes including 13 new compounds and four pairs of epimers with different configurations at C18. These results expand the structural diversity of sesterterpenes and provide important insights for future synthetic biology research.

Twisted leaf like ZnO-flake-like BiOI@CNF grown on ITO substrate as a nanostructured pioneering platform for photoelectrochemical water splitting

Despite ZnO nanostructures garnering significant attention for photoelectrochemical (PEC) water splitting, the quest for efficient ZnO-based photoelectrodes with optimal light absorption, effective electron-hole separation, and transfer remains a challenge. The formation of ZnO heterojunctions with lower bandgap nanostructures of semiconductors has emerged as a strategy to enhance charge transfer while mitigating recombination rates. Additionally, the introduction of carbon nanofibers (CNFs) to these heterojunctions serves to further suppress recombination by electron trapping and enhances catalytic active sites, thereby elevating PEC performance. In this study, twisted leaf-like ZnO, flake-like BiOI, ZnO-BiOI nanostructure heterojunctions, and ZnO-BiOI@C composites were synthesized through a solvothermal method. Notably, the ZnO-BiOI@C photoelectrode exhibited outstanding performance, achieving a photocurrent density of 5.6 mA/cm2 through linear sweep voltammetry under light illumination. Each synthesized photoelectrode demonstrated robust photocurrent responsiveness and excellent stability under chopped conditions for up to 1150 s with a 50 s interval. This remarkable stability is attributed to the unique and stable morphological characteristics and strong crystallinity of the synthesized materials. The formed heterojunction between ZnO-BiOI was found to extend light absorption capabilities, while the incorporation of CNFs effectively trapped electrons from the heterojunction's conduction band, enhancing overall water splitting performance. The results underscore the potential of the ZnO-BiOI@C composite as a high-performing photoelectrode for PEC applications, emphasizing the importance of morphological and compositional considerations in advancing PEC technologies.

Electron-deficient Co7Fe3 induced by interfacial effect of molybdenum carbide boosting oxygen evolution reaction

Developing a high-activity and low-cost catalyst to reduce the anodic overpotential is essential for hydrogen production from water splitting. In this work, a hetero-structured Co7Fe3/Mo2C@C catalyst has been developed to efficiently catalyze oxygen evolution reaction (OER), the overpotential (ƞ10) of Co7Fe3/Mo2C@C-catalyzed OER with current density of 10 mA/cm2 is about 254 mV, substantially lower than the counterparts of Co7Fe3@C-catalyzed OER (ƞ10, 308 mV) and Mo2C@C-catalyzed OER (ƞ10, 439 mV), close to that of OER catalyzed by commercial RuO2. The mechanistic studies reveal that the distinct electron transfer across the Co7Fe3/Mo2C interface results in electron-deficient Co7Fe3, which has been identified as the highly active catalytic sites. Density functional theory (DFT) calculations manifest that Mo2C induces a distinct decrease in electron density on Co7Fe3 and upgrades the d-band centers of Co and Fe in Co7Fe3 towards Fermi energy level, thus substantially lowering the energy barrier of the rate-determining reaction step and conferring significantly improved OER activity on the Co7Fe3/Mo2C@C catalyst.

Synergistic electrochemical catalysis by high-entropy metal phosphide in lithium–sulfur batteries

The shuttle effect and sluggish redox kinetics of polysulfides have hindered the development of lithium–sulfur batteries (LSBs) as premier energy storage devices. To address these issues, a high-entropy metal phosphide (NiCoMnFeCrP) was synthesized using the sol–gel method. NiCoMnFeCrP, with its rich metal species, exhibits strong synergistic effects and provides numerous catalytic active sites for the conversion of polysulfides. These active sites, possessing significant polarity, can bond with polysulfides. In situ ultraviolet–visible were conducted to monitor the dynamic changes in species and concentrations of polysulfides, validating the ability of NiCoMnFeCrP to facilitate the conversion of polysulfides. The batteries with the NiCoMnFeCrP catalyst as functional separators exhibited minimal capacity decay rates of 0.04 % and 0.23 % after 100 cycles at 0 °C and 60 °C, respectively. This indicates that the NiCoMnFeCrP catalyst possesses good thermal stability. Meanwhile, its area capacity can reach 4.78 mAh cm−2 at a high sulfur load of 4.54 mg cm−2. In conclusion, NiCoMnFeCrP achieves the objective of mitigating the shuttle effect and accelerating the kinetics of the redox reaction, thereby facilitating the commercialization of LSBs.

Furosemide Derails Human Lysozyme Fibrillation by Interacting with Aggregation Hot Spots: A Biophysical Comprehension.

Kidney-associated human lysozyme amyloidosis leads to renal impairments;thus, patients are often prescribed furosemide. Based on this fact, the effect of furosemide on induced human lysozyme fibrillation, in vitro, is evaluated by spectroscopic, calorimetric, computational, and cellular-based assays/methods. Results show that furosemide increases the lag phase and decreases the apparent rate of aggregation of human lysozyme, thereby decelerating the nucleation phase and amyloid fibril formation, as confirmed by the decrease in the level of Thioflavin-T fluorescence. Fewer entities of hydrodynamic radii of ∼171 nm instead of amyloid fibrils (∼412 nm) are detected in human lysozyme in the presence of furosemide by dynamic light scattering. Moreover, furosemide decreases the extent of conversion of the α/β structure of human lysozyme into a predominant β-sheet. The isothermal titration calorimetry established that furosemide forms a complex with human lysozyme, which was also confirmed through fluorescence quenching and computational studies. Also, human lysozyme lytic activity is inhibited competitively by furosemide due to the involvement of amino acid residues of the active site in catalysis, as well as complex formation. Conclusively, furosemide interacts with Gln58, Ile59, Asn60, Ala108, and Trp109 of aggregation-prone regions 2 and 4 of human lysozyme, thereby masking its sites of aggregation and generating only lower-order entities that are less toxic to red blood cells than the fibrils. Thus, furosemide slows the progression of amyloid fibrillation in human lysozyme.

Deep removal of COS by carbon aerogel in natural gas: Performance and regeneration on K2O-Cu/CA adsorbent at room temperature

COS in natural gas is difficult to be effectively removed at room temperature. Catalytic hydrolysis is a promising method, however, the discrepancy of catalytic active site as well as deactivation factors are the restricting factors. In this paper, the CuO load and alkali metal modification was successfully prepared on carbon aerogel with more mesoporous structure(5 %K2O-Cu/CA). The doping of K could improve the pore structure of the sample and is more conducive to the storage of sulfate, obtaining good anti-poisoning properties. Meanwhile, the K load achieved enriched surface hydroxyl groups, which played an important role in COS conversion, and provided enough electronic electron transfers to accelerate the H2O dissociation, producing more hydroxyl groups. Then the adsorbed COS could be efficiently captured by the increasing number of weak basic sites at low temperature. Furthermore, after COS transformation the escaped H2S could be subsequently adsorbed on 5 %K2O-Cu/CA surface and converted to be S2- and SO42- on CuO surface. Finally, the adsorbent capacity and deactivation were studied, and the N2 regeneration method owns the higher sulfur capacity of 6.01 mg/g with a COS removal efficiency of 100 % for the first time.

Tandem Catalysts Enabling Efficient C-N Coupling toward the Electrosynthesis of Urea.

The development of a methodology for synthesizing value-added urea (CO(NH2)2) via a renewable electricity-driven C-N coupling reaction under mild conditions is highly anticipated. However, the complex catalytic active sites that act on the carbon and nitrogen species make the reaction mechanism unclear, resulting in a low efficiency of C-N coupling from the co-reduction of carbon dioxide (CO2) and nitrate (NO3 -). Herein, we propose a novel tandem catalyst of Mo-PCN-222(Co), in which the Mo sites serve to facilitate nitrate reduction to the *NH2 intermediate, while the Co sites enhance CO2 reduction to carbonic oxide (CO), thus synergistically promoting C-N coupling. The synthesized Mo-PCN-222(Co) catalyst exhibited a noteworthy urea yield rate of 844.11 mg h-1 g-1, alongside a corresponding Faradaic efficiency of 33.90 % at -0.4 V vs. reversible hydrogen electrode (RHE). By combining in situ spectroscopic techniques with density functional theory calculations, we demonstrate that efficient C-N coupling is attributed to a tandem system in which the *NH2 and *CO intermediates produced by the Mo and Co active sites of Mo-PCN-222(Co) stabilize the formation of the *CONH2 intermediate. This study provides an effective avenue for the design and synthesis of tandem catalysts for electrocatalytic urea synthesis.

Study on Water Splitting of the 214-Type Perovskite Oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga).

We present a study on the electrocatalysis of 214-type perovskite oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga) with semiconducting-like behavior synthesized using the sol-gel method. Among these five catalysts, PrSrCoO4 exhibits the optimal electrochemical performance in both the oxygen evolution reaction and the hydrogen evolution reaction, mainly due to its larger electrical conductivity, mass activity, and turnover frequency. Importantly, the weak dependency of LSV curves in a KOH solution with different pH values, revealing the adsorbate evolving mechanism in PrSrCoO4, and the density functional theory (DFT) calculations indicate that PrSrCoO4 has a smaller Gibbs free energy and a higher density of states near the Fermi level, which accelerates the electrochemical water splitting. The mutual substitution of different rare-earth elements will change the unit-cell parameters, regulate the electronic states of catalytic active site Co ions, and further affect their catalytic performance. Furthermore, the magnetic results indicate strong spin-orbit coupling in the electroactive sites of Co ions in SmSrCoO4 and EuSrCoO4, whereas the magnetic moments of Co ions in the other three catalysts mainly arise from the spin itself. Our experimental results expand the electrochemical applications of 214-type perovskite oxides and provide a good platform for a deeper understanding of their catalytic mechanisms.

Tandem Catalysts Enabling Efficient C−N Coupling toward the Electrosynthesis of Urea

AbstractThe development of a methodology for synthesizing value‐added urea (CO(NH2)2) via a renewable electricity‐driven C−N coupling reaction under mild conditions is highly anticipated. However, the complex catalytic active sites that act on the carbon and nitrogen species make the reaction mechanism unclear, resulting in a low efficiency of C−N coupling from the co‐reduction of carbon dioxide (CO2) and nitrate (NO3−). Herein, we propose a novel tandem catalyst of Mo‐PCN‐222(Co), in which the Mo sites serve to facilitate nitrate reduction to the *NH2 intermediate, while the Co sites enhance CO2 reduction to carbonic oxide (CO), thus synergistically promoting C−N coupling. The synthesized Mo‐PCN‐222(Co) catalyst exhibited a noteworthy urea yield rate of 844.11 mg h−1 g−1, alongside a corresponding Faradaic efficiency of 33.90 % at −0.4 V vs. reversible hydrogen electrode (RHE). By combining in situ spectroscopic techniques with density functional theory calculations, we demonstrate that efficient C−N coupling is attributed to a tandem system in which the *NH2 and *CO intermediates produced by the Mo and Co active sites of Mo‐PCN‐222(Co) stabilize the formation of the *CONH2 intermediate. This study provides an effective avenue for the design and synthesis of tandem catalysts for electrocatalytic urea synthesis.