Catalytic Active Sites Research Articles

Bimetal anchoring porous MXene nanosheets for driving tandem catalytic high‐efficiency electrochemical nitrate reduction

AbstractElectrochemical nitrate reduction reaction (NO3RR) is considered a promising strategy for ammonia synthesis and nitrate removal, in which catalyst development is crucial. Herein, a series of bimetal (Co and Cu) anchoring porous MXene nanosheets (CoxCuy@PM) catalysts were prepared by combining etching and reduction strategy. On the one hand, Cu and Co bimetals provided tandem catalytic active sites for NO3RR. On the other hand, the in‐plane PM exhibited good electrical conductivity and multiple transport pathways. Consequently, the optimized Co7Cu3@PM catalyst achieved a high ammonia yield of 7.43 mg h−1 mg cat.−1 and an excellent Faraday efficiency (FE) of 95.9%. The mechanism of NO3RR was investigated by analyzing electrolysis products and in situ Fourier transform infrared spectroscopy. Furthermore, the Co7Cu3@PM based ZnNO3− battery exhibited the superior power density of 5.59 mW cm−2 and an NH3 FE of 92.3%. This work presents an effective strategy to design MXene‐based high‐performance NO3RR electrocatalysts.

Triggering Asymmetric Layer Displacement Polarization and Redox Dual-Sites Activation by Inside-Out Anion Substitution for Efficient CO2 Photoreduction.

Sluggish bulk charge transfer and barren catalytic sites severely hinder the CO2 photoreduction process. Seeking strategies for accelerating charge dynamics and activating reduction and oxidation sites synchronously presents a huge challenge. Herein, an inside-out chlorine (Cl) ions substitution strategy on the layered polar Bi4O5Br2 is proposed for achieving layer structure-dependent polarization effect and redox dual-sites activation. Cl ions in the bulk phase shrink the halogen layer interspace by 8‰, triggering asymmetric [Bi4O5]2+ layer displacement polarization, prolonging the average photocharge lifetime to 201.8ps. Meanwhile, surface substituted Cl ions enhance the electron-donating capability of neighboring Bi atoms, activating the intrinsic Bi reduction sites, and increasing H2O molecule adsorption on nearby intrinsic O oxidation site (cal. by 0.105eV), also self-donating as an alien oxidation site. Besides, Cl upshifts the p-band center closer to the Fermi level, facilitating the reactant adsorption. Therefore, the energy barrier for CO2 activation and rate-limiting *COOH intermediate formation steps are significantly decreased. Without cocatalysts and sacrificial reagents, inside-out Cl-substituted Bi4O5Br2 delivers a remarkable CO2-to-CO photoreduction rate of 50.18µmol g-1 h-1, being one of the state-of-the-art catalysts. This finding offers insights into exploiting polarization at the molecular-level and enhances understanding of catalytic site activation.

Atomic Level Understanding of the Structural Stability and Catalytic Activity of Nanoporous Gold/Titania Cluster Inverse Catalysts at Ambient and High Temperatures.

Nanoporous gold (NPG) exhibits exceptional catalytic performance at low temperatures, but its activity declines at elevated temperatures due to structural coarsening. Loading metal oxide nanoparticles onto NPG can enhance its catalytic activity at high temperatures. In this work, we used NPG-supported titania nanoparticles as a model system (denoted as Ti2O4/NPG) to study their catalytic activity at ambient and high temperatures with CO oxidation as a probe reaction by density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD) simulations. The possible factors that may affect the CO oxidation reaction pathways and energy profiles on the Ti2O4/NPG, such as oxygen vacancies; silver impurities; Mars-van Krevelen (MvK), Eley-Rideal (ER), or trimolecular Eley-Rideal (TER) mechanisms; and catalytic active sites, were comprehensively investigated. The results showed that reaction energy barriers on Ti2O4/NPG were not significantly decreased compared to the pristine NPG, indicating that their catalytic activities at ambient temperature were comparable. At the evaluated temperature (400 °C), the Ti2O4/NPG exhibited superior thermal stability and maintained its active sites, while the NPG reduced active sites due to surface coarsening. The strong oxide-metal interaction (SOMI) effect between the NPG and Ti2O4 nanoparticles is found to be a main factor for the high structural stability and catalytic activity at high temperatures.

Discovery of 5-(Substituted Phenyl)-2-aryl Benzimidazole Derivatives as SIRT1 Activators: Their Design, in silico Studies, Synthesis, and in vitro Evaluation.

Silent information regulator two homologue one (SIRT1) is an emerging target for managing metabolic disorders. This study aimed to synthesize novel 5-(- substituted phenyl)-2-aryl benzimidazole derivatives and evaluate them for SIRT1 activation. The compounds were designed according to the findings of the QSAR models framed in our previous studies. Molecular docking and dynamics studies were also performed to explore the interactions of designed compounds with the active site of the SIRT1 enzyme using AutoDock Vina and Schrödinger Maestro version 11.8.012, respectively. Compounds with good binding affinity were synthesized by Suzuki-Miyaura cross-coupling and spectrally characterized. The molecules were evaluated for their in vitro SIRT1 activation properties using a fluorescent screening kit. Based on the results of in vitro assay, a structure-activity relationship was established. SwissADME was employed to calculate the pharmacokinetics characteristics of the synthesized molecules. The molecular docking studies revealed that all the activators were effectively docked in the catalytic active site. All compounds demonstrated interactions with important amino acids like Glu230 and Arg446. In molecular dynamics simulations, the root mean square deviation (RMSD) of compound 5m and protein SIRT1 remained stable, i.e., below 3mm. Compound 5m, 4-(2-(3,4-dihydroxy-5-nitrophenyl)-1H-benzo[d]imidazol- 5-yl)benzaldehyde, was the most potent compound with an EC50 value of 0.006 mM (±0.001) and maximum activation of 240.5%. All the synthesized compounds had acceptable theoretical ADME profiles, and drug-likeness properties complied with Lipinski's rule. According to the findings, synthesized compounds may be viable leads for SIRT1 activators and may be used to advance preclinical in vivo research utilizing animal models.

Elaborate construction of a MOF-derived novel morphology Z-scheme ZnO/ZnCdS heterojunction for enhancing photocatalytic H2 evolution and tetracycline degradation

Elaborate construction of novel Z-scheme heterojunction with exceptional morphology derived from metal-organic framework (MOF) have been attracted greatly interest for improving the photocatalytic ability. Herein, a Z-scheme ZnO/ZnCdS heterojunction of rare morphology with ultrathin-nanosheet assembled hierarchical morphology ZnCdS supporting on rich gap ZnO nanospheres were constructed from Zn-based MOF (namely PZH-139) for the first time. This unique feature increased specific surface area, offered abundant mass transport channels and accessible catalytic active sites, accelerated electron migration, which highly elevated photocatalytic property. Furthermore, electron paramagnetic resonance (EPR) measurements and density functional theory (DFT) calculations confirmed the reservation of strong redox capability owing to Z-scheme electron transfer path and the ΔGH* closer to zero of Z-scheme ZnO/ZnCdS system were another two key factors for boosting the photocatalytic activity. As a result, 3-ZnO-700/ZnCdS-160 with optimal morphology showed the best H2 generation performance of 15.43 mmol h−1 g−1 and degradation tetracycline (TC) efficiency of 98.14 %. This work offered a novel and feasible idea for elaborate synthesis of the high-efficiency Z-scheme ZnO/ZnCdS heterojunction with special morphology derived from Zn-MOF.

Pd nanoparticles on DUT-67-PZDC-derived N-doped carbon for efficient H2 generation from formic acid dehydrogenation

It is important to develop heterogeneous catalysts with high efficiency and stability to catalyze formic acid (FA, HCOOH) dehydrogenation. Herein, through pyrolysis of DUT-67-PZDC and etching in a hydrofluoric acid (HF) solution, the HF-etched N-doped carbon (HNDC) carrier was obtained. Palladium nanoparticles (Pd NPs), with an average particle size of 3.0 nm, were prepared on the HNDC support using a simple chemical co-reduction method. The optimized Pd/HNDC catalyst demonstrates excellent catalytic activity, the initial turnover frequency (TOF) value is 6001 h−1 at 50 °C with the incorporation of sodium formate (SF) as an additive, and the FA conversion and hydrogen (H2) selectivity could be up to 100%, which is comparable to the majority of MOF-derived heterogeneous catalysts published to date. Additionally, the Pd/HNDC can maintain good stability in five consecutive FA dehydrogenation runs with only a slight decrease. Such remarkable catalytic performance of Pd/HNDC is mainly ascribed to the unique structure of HNDC support with high surface area and hierarchical pore characteristic, the strong synergistic interaction between Pd NPs and the N sites on HNDC, as well as the ultrasmall size and high dispersion of Pd NPs as the catalytic active site. This work offers an efficient method for assembling highly active catalysts for FA dehydrogenation.

Computational insights into dispiro-oxindolopyrrolizidines as aldose reductase inhibitors: Molecular docking, ADME analysis, molecular dynamic simulation, and MM-PBSA analysis

Chronic diabetes problems arise from the activation of aldose reductase (AR), the primary enzyme of the polyol pathway, under hyperglycemic circumstances. The spirooxindole ring system comes out to be a fascinating class of naturally occurring compounds with pharmaceutical interest. In this work, we have chosen three dispirooxindolopyrrolizidines (DSOIP-H, DSOIP-Me, and DSOIP-OMe) to investigate their ability to inhibit AR. Through molecular docking studies, the order of binding energy was calculated as DSOIP-H (-8.23 kcal/mol) < DSOIP-Me (-8.58 kcal/mol) < DSOIP-OMe (-8.72 kcal/mol). The three ligands showed effective binding with AR's catalytic active site through hydrophobic interactions. The ADME analysis revealed valuable insights into the ligands' pharmacokinetic properties. Through protein-ligand interactions, DSOIP-OMe consistently interacted with the amino acid residues of the AR enzyme's active site areas, as demonstrated by the molecular dynamic (MD) trajectory analysis. The exceptional inhibitory efficacy of DSOIP-OMe has been established based on its binding energy values of -92.69 kJ/mol as determined by MM-PBSA. The PHE122 residue of AR is recognized as a crucial residue that made a substantial contribution to the binding energy of MM-PBSA through hydrophobic interactions.

Poly(ADP-Ribose) Polymerase (PARP) Inhibitors for Cancer Therapy: Advances, Challenges, and Future Directions.

Poly(ADP-ribose) polymerases (PARPs) are crucial nuclear proteins that play important roles in various cellular processes, including DNA repair, gene transcription, and cell death. Among the 17 identified PARP family members, PARP1 is the most abundant enzyme, with approximately 1-2 million molecules per cell, acting primarily as a DNA damage sensor. It has become a promising biological target for anticancer drug studies. Enhanced PARP expression is present in several types of tumors, such as melanomas, lung cancers, and breast tumors, correlating with low survival outcomes and resistance to treatment. PARP inhibitors, especially newly developed third-generation inhibitors currently undergoing Phase II clinical trials, have shown efficacy as anticancer agents both as single drugs and as sensitizers for chemo- and radiotherapy. This review explores the properties, characteristics, and challenges of PARP inhibitors, discussing their development from first-generation to third-generation compounds, more sustainable synthesis methods for discovery of new anti-cancer agents, their mechanisms of therapeutic action, and their potential for targeting additional biological targets beyond the catalytic active site of PARP proteins. Perspectives on green chemistry methods in the synthesis of new anticancer agents are also discussed.

Boosted Persulfate Activation Using Ba2CoMnO5 and LDH/CaCO3 for Amoxicillin Degradation: A Comparative Study

AbstractSulfate radicals based advanced oxidation processes (SR‐AOPs) have gained attention recently due to their high mineralization capability in environmental remediation. The high persulfate (PS) activation activity of cobalt‐based semiconductors has epitomized them as preferred catalysts for SR‐AOPs but shortcomings such as leaching, and loss of catalytic active sites limit their applicability. Herein, two different strategies are employed to minimize leaching and improve charge transportation and separation for efficient PS activation under visible light irradiation using LDH/CaCO3/PS and Ba2CoMnO5/PS AOP systems synthesized by solid state method. LDH/CaCO3/PS achieved 17.9% higher reaction rate than Ba2CoMnO5/PS for degradation of amoxicillin (AMX) with higher TOC mineralization efficacy. Despite SO4•− and OH• existence and involvement in both systems, the degradation pathways mapped from QTOF‐HPLC‐MS data demonstrated formation of different pathways during AMX mineralization. This work demonstrates novel fabrication of brownmillerite double layered perovskite and insulator supported LDH for environmental pollution remediation.

Polyoxometalates@Metal-Organic Frameworks: Synthesis Strategies, Nanostructure Modulation and Application in Biomass Conversion.

Polyoxometalates@metal-organic frameworks (POMs@MOFs) have attracted much attention as multifunctional materials in biomass catalysis. Individual POMs and MOFs are hindered by their respective defects, such as poor stability and single catalytic active site, which make it difficult to realize large-scale applications. However, the combination of POMs and MOFs can be used to maximize the catalytic advantages of each. MOFs with high specific surface area and rich pore structure can effectively stabilize and uniformly disperse POMs, while the introduction of POMs also provides more catalytic possibilities for POMs@MOFs. Therefore, POMs@MOFs with ultra-high porosity, large specific surface area and excellent acid catalytic activity have unique catalytic advantages in the field of biomass catalytic conversion. In this work, we provide an overview of the current development of POMs@MOFs in the field of biomass catalysis. The synthesis strategies of POMs@MOFs are summarized and discussed, highlighting the in-situ synthesis methods. We focus on the nanostructure engineering of POMs@MOFs, and explore the "structure-property" relationship in depth. In addition, the representative work of POMs@MOFs in the catalysis of biomass derivatives is summarized. Filially, the prospects, and challenges for the future development of POMs@MOFs in the field of biomass catalysis are also presented.

NiCoP/CoP2 nanoparticles supported on sugarcane bagasse carbon as the electrocatalyst with excellent catalytic performance towards the hydrogen evolution reaction

Sugarcane bagasse carbon (SCBC) was synthesized and used to support NiCoP/CoP2 nanoparticles (NiCoP/CoP2-SCBC), and its electrocatalytic performance for the hydrogen evolution reaction (HER) was investigated and compared with that of NiCoP/CoP2 nanoparticles and NiCoP/CoP2 nanoparticles supported on carbon black (NiCoP/CoP2-C). Impressively, NiCoP/CoP2-SCBC shows the best electrocatalytic performance for HER with an over-potential of 159.5 mV at 10 mA cm-2 and a Tafel slope of 67.24 mV dec-1, along with the excellent stability. This outstanding performance is partly attributed to the abundant hydroxyl functional groups in SCBC, which can make the catalyst have better dispersion and a higher proportion of Ni2+. In addition, SCBC can lead to more defects in NiCoP/CoP2, and SCBC contains a large number of P elements, which can increase the catalytic active sites and contribute to the fast HER process to some degree.

Phosphorus doping heterostructure La(OH)3@CuO @NF as an advanced electrocatalyst for the oxygen evolution reaction

Due to the prevailing energy shortages, the pursuit of new alternative energy sources is becoming increasingly urgent. Hydrogen production through water electrolysis has emerged as a crucial method. However, the sluggish four-electron reaction in the oxygen evolution reaction (OER) remains the primary rate-limiting step. In this study, we synthesized a heterostructure La(OH)3@CuO-P material on the nickel foam (NF) substrate. The experimental results demonstrate that after phosphating treatment, the heterostructure La(OH)3@CuO-P exhibits exceptional catalytic performance with only 215 mV overpotential, a Tafel slope value of 79.36 mV/dec, and a bilayer capacitance of 39.02 mF/cm2 at a current density of 10 mA/cm2 for OER in a 1 M KOH solution. These values are significantly superior compared to those obtained using heterostructure La(OH)3@CuO alone which showed an overpotential value of 365 mV at a current density of 10 mA/cm2. Moreover, during cyclic voltammetry testing for up to 500 cycles, La(OH)3@CuO-P also demonstrates relatively stable performance. Analyses suggest that composite heterostructure effectively addresses issues such as insufficient conductivity of La(OH)3 and monomer aggregation tendency for CuO while maintaining excellent properties for each component. By incorporating P atoms as dopants, the interaction between La, Cu, and P atoms not only facilitates fine-tuning of the electronic structure and optimization of the adsorption free energy (-OH), but also promotes an increase in catalytic active sites through sample size reduction, thereby further augmenting the performance of the OER.

Boosting low-temperature NH3-SCR performance via mixed-valence cobalt dual active sites

Nitrogen oxides (NOx) have become a critical environmental concern, necessitating the development of highly efficient catalysts for temperature which is lower than 300 °C. Selective catalytic reduction with NH3 (NH3-SCR) is a process where ammonia is the reducing agent for selective catalytic reduction of nitrogen oxides in exhaust gases. The mechanism-property relationship between catalytic active sites and low-temperature denitrification efficiency, however, remains unclear. In this study, we synthesized a series of cobalt-modified nanoparticle catalysts using a scalable citric acid sol-gel method and conducted comprehensive characterizations. Our findings indicate that an optimal cobalt doping rate significantly enhances catalytic activity due to the synergistic effects of reduced nanoparticle size and the dual active sites of Co0/Co2+. Specifically, at a cobalt doping ratio of 1.0, the catalyst demonstrates peak SCR activity, achieving 85.5% NOₓ conversion at 120 °C and complete conversion at 150 °C. These cobalt-modified nanoparticle catalysts feature high deposition of doped Co ions on their surfaces, predominantly as metallic cobalt and CoOx nanoclusters. Compared to undoped samples, the cobalt-doped nanoparticle catalysts exhibit a greater specific surface area, increased acidity, enhanced chemisorbed oxygen, and improved redox properties, all contributing to superior denitrification efficacy. Additionally, Density Functional Theory (DFT) calculations provide assertive evidence into the reaction mechanism, showing that Co2+ sites effectively adsorb and activate NH₃, while Co0 sites are crucial for NO adsorption and activation. The synergistic interaction between Co2+ and Co0 facilitates NN coupling, enhancing overall reaction efficiency. These findings underscore the potential of cobalt-modified catalysts for practical industrial applications, offering robust performance over a wide temperature range and meeting stringent environmental regulations.

NixB/Mo0.8B3 Nanorods Encapsulated by a Boron‐Rich Amorphous Layer for Universal pH Water Splitting at the Ampere Level

AbstractHeterostructured interfaces are crucial to electrocatalysts for water splitting. Herein, coral‐like multiheterostructured NixB/Mo0.8B3 (NMB) nanorods encapsulated by a boron‐rich amorphous layer are prepared for water splitting. Density‐functional theory (DFT) calculations indicate that the NMB interface adjusts the d‐band center and electronic structure of the molybdenum sites. Owing to the strong electronic coupling between Ni, Mo, and B at the heterojunction, large number of exposed catalytic active sites, as well as the special hydrophilic characteristics endowed by the surrounding amorphous layer, the NMB catalyst exhibits remarkable universal‐pH hydrogen evolution reaction (HER) activity with low overpotentials (η) of 15, 26, and 83 mV to deliver 10 mA cm−2 in basic, acid, and neutral media, respectively, and outstanding oxygen evolution reaction (OER) characteristics in the basic medium with η10 and η500 of 170 and 420 mV, respectively. The unique self‐supporting 3D hierarchical interconnected structure facilitates mass transport thus leading to high mechanical stability for 450 and 200 h in HER and OER at ≈1000 mA cm−2. More importantly, the NMB exhibits excellent performance toward overall‐water electrolysis as a bifunctional catalyst with ultralow cell voltages of 1.45/1.56/1.85 V @ 10/100/1000 mA cm−2, demonstrating the large potential in industrial water splitting applications.

Enhanced power generation by carbonized microsphere embedded with bimetallic carbides nanoparticles as efficient electrocatalyst in bioenergy harvesting systems

The performance and preparation method of anode are the key factors for power generation and magnified application of microbial fuel cell (MFC). This is because the anode plays an essential role in whole process for extracellular electron transfer (EET) as the carrier of exoelectrogens. In this work, dual-phased Mo2C-W2C microsphere are prepared on carbon-based matrices as binder-free anode by in-situ pyrolysis of Mo/W precursors. As expected, the Mo2C-W2C/CC anode exhibits brilliant electrocatalytic activity, electron harvesting capacity and improved EET rate, thus the maximum power density of corresponding MFC achieves 4.89 W/m2. The above enhancement can be attributed to the microspherical three-dimensional structure consisting of numerous carbon nanosheets embedded with Mo2C-W2C heterogeneous nanoparticles, which will provide more catalytic active sites for microbial metabolic reactions. The microbial community analysis indicates that the formation of electroactive biofilms has been promoted by the selective screening of Mo2C-W2C for exoelectrogens and other bacteria related to sulfur metabolism. Finally, the bioenergy harvesting system assembled with Mo2C-W2C electrocatalyst successfully charges the 12 V battery. This study provides a facile, low-cost modification method for the development of high-performance MFC anodic materials conducive to large-scale preparation and has a promising effect in practical application.

MnO2/rGO bifunctional catalyst and support materials for gel polymer electrolyte based Zn-air batteries

A high-performance and long-lasting, rechargeable Zn-air battery requires a reliable and effective bifunctional catalyst material to facilitate the oxygen reduction and oxygen evolution reactions during the battery operation. Manganese oxide (MnO2) is a promising non-precious perspective due to its multivalency and various polymorphic structures that effectively catalyze oxygen evolution and reduction. In the present work, MnO2 nanowires (NWs) have been integrated with over-reduced graphene oxide (rGO) in various concentrations via a facile hydrothermal route. The synthesized materials, tested in lab-made zinc-air battery devices fabricated using gel polymer electrolyte, exhibit a significant enhancement in the performance and 2–3 times the cycle life compared to the bare MnO2. The ZAB device was tested for galvanostatic charge-discharge technique, and results exhibit a cycle life of 165 h (495 cycles@20 min per cycle) when discharged up to 1.0 V at a current density of 5.2 mA/cm2 and displayed a capacity of 731 mAh/gZn. Reduced graphene oxide acts as a support material that enhances the conductivity and surface area of the active material and also provides active sites for catalysis. This work signifies the importance of the engineering of the catalyst, support material, and additives, as slight changes may result in a significant enhancement in the cycle life.The appropriate composition of catalyst and support material and a compatible gel polymer electrolyte facilitates the fabrication of flexible zinc-air batteries for various applications.

Bifunctional Mott-Schottky-type Co-Fe3N electrocatalyst as sulfur host and separator modifier to enhance the transformation kinetics of Li2S

Recently, lithium-sulfur batteries (LSBs) with ultra-high theoretical energy density attract the attention of researchers. However, the shuttle of lithium polysulfides (LPSs) seriously restrict the development of LSBs. Here, Co-Fe3N with Mott-Schottky type exhibits exceptional chemisorption and catalytic capabilities towards LPSs. The Co-Fe3N Mott-Schottky heterojunction induces charge redistribution at the heterogeneous interface, thereby increasing the rate of charge transfer, enhancing chemisorption ability, and reducing the energy barrier for S8 reduction and Li2S oxidation. The Co metal provides more catalytic and adsorption active sites for the conversion of LPSs and further improves the catalytic activity of Fe3N. Under the synergistic effect of the metal Co and Fe3N, the redox reaction of LPSs is improved, and the nucleation/decomposition energy barriers of Li2S are decreased, realizing the multifunctional coupling of adsorption-catalytic-conversion of LPSs. The LSBs with Co-Fe3N/S cathode and Co-Fe3N-PP separator exhibits a low capacity decay of 0.067 % per cycle at 1 C during 400 cycles. Even at a high sulfur loading of 3.1 mg cm−2, the LSBs delivers a reversible capacity of 1016 mA h g−1 at 0.1 C. The utilization of the Co-Fe3N with Mott-Schottky type in LSBs presents a novel approach towards designing multifunctional coupled materials with adsorption-catalysis-conversion capabilities.

Electronic synergy between NiCo2O4 and adjacent carbon defects to enhance styrene cracking activity for styrene-saturated activated carbon regeneration

The design and construction of catalysts featuring abundant electron transfer and defect structures for the regeneration of styrene-saturated activated carbon (AC) pose a significant challenge. This paper presents successful preparation of a regenerated adsorbent with synergistic catalytic active sites of NiCo2O4 spinel and carbon defects using a simple impregnation method. Enhanced catalytic activity is attributed to the electronic synergy between NiCo2O4 and carbon defects in 2.5Ni-2.5Co-900, involving substantial electron transfers, abundant acidic sites, and strong reducibility. Reactive oxygen species and the robust oxygen transfer facilitate the deep oxidation of intermediates and carbon elimination. The optimized regenerated adsorbent achieved a styrene adsorption capacity of 446.4mg/g with a recovery of 92.4% of the fresh sample, which is 1.5 times higher than 5Ni-900 and about 1.8 times higher than the unmodified regenerated activated carbon sample, RAC-900. The mechanism of styrene cracking and the evolution of intermediates were investigated using thermogravimetric-infrared coupling, and the effects of catalytic temperature and active sites on styrene cracking, deep oxidation of intermediates, and elimination of carbon deposits were explored. Kinetic analysis demonstrated that the adsorption of styrene on regenerated samples entailed a multifaceted process integrating both physical and chemical adsorption. The significance of chemical adsorption became increasingly evident as the concentration of defective sites grew. Intra-pore diffusion is the main determining step of the adsorption process. After five cycles, the adsorption capacity of 2.5Ni-2.5Co-900 decreased to below 25%, suggesting promising strategies to overcome challenges of regenerating styrene-saturated AC.

Graphene‐Transition Metal Electrocatalysts for Sustainable Water Electrolysis

AbstractTransition metal compounds (TMCs) are potentially fruitful substitutes for noble metals for electrocatalytic splitting of water due to their intrinsic electrocatalytic activity, modifiable morphology, tunable electronic structure and their earth‐abundance. The combination of TMCs with graphene improves the dispersion of loaded catalysts, providing more catalytic active sites, enhancing the conductivity of hybrids, affording accelerated charge‐transfer kinetics, and minimizing catalyst bleaching, aggregation, and sintering under harsh reaction conditions. Additionally, graphene incorporation into TMCs modulates the electronic structure of active centers because of the synergistic interaction between them, thereby improving their catalytic performance. This review paper focuses on the recent progress made in designing different graphene‐transition metal‐based materials that can be used in the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and overall water splitting (OWS). In‐situ characterization methodologies and DFT calculations that facilitate catalyst development are discussed elaborately. Finally, the advancements made in the development of graphene‐supported transition metal compounds for use in a functional water electrolyzer have been explored. In conclusion, a few specific recommendations have been made about the current challenges related to the widespread production of effective HER/OER electrocatalysts for water electrolysis.

Tailoring rGO[sbnd]Cu-Cu2O as a three-dimensional catalytic system in boosting of methanol electro-oxidation reaction

Tailoring a reduced graphene oxide-Cu-Cu2O (rGOCu-Cu2O) as a three-dimensional (3D) integrated catalytic system via an in-situ potential-controlled electrodeposition approach is a feasible pathway to boost methanol oxidation reaction (MOR) for direct methanol fuel cell. The enhancement in catalytic functionality and performances is due to the synergistic interaction between the in-situ electroreduced graphene oxide (rGO) and copper metal ions over it. The sequential and synergistic effect of the co-deposition potential, optimized time, and probable corrosion-promotion effect (formation of a galvanic cell between rGO and copper due to entrapped dissolved oxygen) is believed to be responsible for the structural growth of as-developed 3D catalytic systems. The MOR results suggest that the composite material deposited at the higher cathodic deposition potential (-1.2 V vs SCE), i.e., rGOCu (c) featured the remarkable lowest onset oxidation potential (i.e., +0.37 V), peak potential (i.e., +0.73 V), peak current density (135.76 mAcm−2), potentiostatic durability at +0.6 V after 3.5 h (∼65.85 mAcm−2) and outstanding cyclic stability (∼97.7 % current retention after 500 cycles), which is superior to the other modified composite electrodes. The enhanced performances are due to the effective dissociative adsorption of methanol from the available active catalytic site's and the presence of hydroxyl groups which has probably improved the oxidation of adsorbed intermediates from the surface. Further, Fourier-transform infrared (FT-IR) experiments revealed that formate as an active intermediate is being generated on all three rGOCu-Cu2O modified electrodes and follows the non-CO reaction pathway for direct oxidation of methanol.