As-prepared Catalysts Research Articles

Construction of Mo2TiC2Tx MXene as a Superior Carrier to Support Ru-CuO Heterojunctions for Improving Alkaline Hydrogen Oxidation.

The sluggish anodic hydrogen oxidation reaction (HOR) of the hydroxide exchange membrane fuel cell (HEMFC) is a significant barrier for practical implementation. Herein, we designed a catalyst of Mo2TiC2Tx MXene-supported Ru-CuO heterojunctions (named as Ru-CuO/MXene). The XPS spectra and the d-band center data of the different amounts of Cu of the Ru-CuO/MXene suggested that there existed a strongly electronic metal-support interaction between the active species and the substrate with MXene as the excellent carrier. Furthermore, the in situ electrochemical experimental results (operando electrochemical impedance spectroscopy and in situ electrochemical Raman spectroscopy) and density functional theory (DFT) calculations showed that Ru and CuO were the optimal adsorption sites for surface species *H and *OH, respectively, endowing Ru-CuO/MXene with the ability to weaken the hydrogen binding energy (HBE) and strengthen the hydroxide binding energy (OHBE). Remarkably, the optimized catalyst modified an impressive HOR activity in the 0.1 M KOH electrolyte with a kinetic and an exchange current density of 7.63 and 1.37 mA cm-2 at 50 mV overpotential (vs. RHE), respectively, which were 1.98- and 1.2-fold higher than those of commercial Pt/C (20 wt %). Finally, the as-prepared catalyst also exhibited superior durability and exceptional CO antipoisoning ability in 1000 ppm of the CO/H2-saturated 0.1 M KOH electrolyte. This work provides an inspiring strategy to design high-activity HOR electrocatalyst-based metallic Ru in alkaline environments.

Engineering the electron localization of metal sites on nanosheets assembled periodic macropores for CO2 photoreduction

Photocatalytic conversion of CO2 into syngas is highly appealing, yet still suffers from the undesirable product yield due to the sluggish carrier transfer and the uncontrollable affinity between catalytic sites and intermediates. Here we report the fabrication of Co sites with tunable electron localization capability on two dimensional (2D) nanosheets assembled three dimensional (3D) ordered macroporous framework (3DOM-NS). The as-prepared Co-based 3DOM-NS catalysts exhibit attractive photocatalytic performances toward CO2 reduction, among which the cobalt sulfide one (3DOM Co-SNS) shows the highest syngas generation rate up to 347.3 μmol h−1 under the irradiation of visible light and delivers a remarkable catalytic activity (1150.7 μmol h−1) in a flow reaction system under natural sunlight. Mechanism studies reveal that the high electron localization of metal sites in 3DOM Co-SNS strengthens the interaction between Co and HCOO* via the orbital interactions of dyz/dxz-p and s-s, thus facilitating the cleaving process of C-O bond. Additionally, the ordered macroporous framework with nanosheet subunits elevates the transfer efficiency of photoexcited electrons, which contributes to its high activity.

Nicup Catalyst with the Synergistic Effect of Ni and Cu for Hydrogen Production Using Ammonia Electrolysis

Carbon neutrality using cleaner energy sources to replace fossil fuels is essential for climate change and a sustainable future. There are many candidates, including renewable energy, but hydrogen energy is gaining the most attention. Hydrogen energy is the most attractive alternative due to its abundance, renewability, and eco-friendliness as an energy source, however, its utilization is limited by transportation challenges. To solve this issue, various hydrogen carriers have been studied. Among them, ammonia is considered the closest to commercialization because it has an existing transportation infrastructure and does not contain carbon. In addition, ammonia can be electrochemically hydrogenated, and the theoretical reaction potential for this is 0.07 V vs. RHE, which is significantly lower than water electrolysis (1.23 V vs. RHE). Nevertheless, the actual reaction occurs at a potential between 1 and 2 V due to the high overpotential generated by the adsorption of NHx species on the surface during the reaction. Pt also has weaknesses like toxicity due to high nitrogen adsorption capacity, and its high price. To improve this, developing effective catalysts based on non-precious metal materials is important. In this study, a catalyst was synthesized using Ni, which has excellent nitrogen adsorption and ammonia oxidation reaction (AOR) properties, and Cu, which has desorption and dimerization properties of NHX species. Moreover, its phosphorylation improves catalyst durability and provides additional reaction sites. The as-prepared catalysts were characterized by physicochemical properties and electrochemical analysis along with the comparator, and the potential at 100 mA for AOR was 1.45 V vs. RHE. The catalysts were also evaluated for stability and hydrogen generation.

Tuning the Electronic Structure of Iridium-Based OER Electrocatalysts by Particle Proximity and Metal-Support Interactions Probed by Operando XAS

Iridium (Ir) is a widely used anode electrocatalyst material for the oxygen evolution reaction (OER) in PEM water electrolysis.[1] However, high loadings of very costly and scarce Ir are currently needed to achieve sufficient performance and durability, which hinder the broad implementation of large-scale PEM water electrolyzers. To overcome these challenges, size-controlled Ir nanoparticles (NPs)[2] are typically used with different loadings in combination with robust support materials such as titanium dioxide (TiO2)[3] or antimony doped tin oxide (ATO)[4]. The variation of the metal loading and support material allows tailoring the metal-support interactions (MSI) and particle proximity effect based on the interparticle distance. Although the particle proximity effect of other catalyst material systems, e.g. Au NPs supported on TiO2 [5], is well-established, the influence of different support materials and loadings (interparticle distance) on the OER activity and durability for Ir NPs catalysts are not fully understood to date.This study focuses on the metal-support interactions (MSI) and particle proximity effect for Ir NPs deposited on three different support materials: antimony doped tin oxide (ATO), titanium oxide (TiO2) and graphitized carbon (C) at different metal loadings between 20 – 60 wt.%. First, surfactant-free Ir NPs with controlled particle size were obtained by a colloidal route in methanol.[2] Afterwards, the Ir NPs were homogeneously distributed on the support materials with similar loadings and particle sizes and characterized by TEM and XPS. Thin-film rotating disc electrode (TF-RDE) technique was employed to determine the OER activity in 0.05°M H2SO4 electrolyte solution. The ex-situ XAS and XPS data show significant differences in oxidation behavior of Ir depending on the loading and support material. Interestingly, the OER mass activity at 60 wt.% Ir loading increases in the order: TiO2 (36 ± 4 A/gIr) < C (54 ± 5 A/gIr) < ATO (92 ± 8 A/gIr) measured at 1.5 VRHE-iR and 25 °C. Although the NPs on the support materials are aged similar, the iridium on TiO2 is more strongly oxidized than on ATO. In addition to the effect of the support material, the proportion of oxidized iridium increases with decreasing loading. However, no changes in the chemical state of Ir as a function of the loading for TiO2 support material used are observed.Furthermore, operando XAS investigations on the as-prepared Ir catalysts were preformed to correlate the OER activity and stability with the loading and support material. The operando Ir LIII edge XAS experiments were performed at the P64 beamline at DESY and the ID24 beamline at the ESRF using a home-made spectro-electrochemical flow cell consisting of a three-electrode configuration. Cyclic voltammetry (CV) measurements were performed using two different protocols. The first protocol included a fixed lower vertex potential and starting from 0.06 VRHE, with increasing upper vertex potentials of 0.8, 1.2, 1.4, or 1.6 VRHE. The second protocol used a fixed upper vertex potential of 1.6 VRHE as the starting point, and a variable lower vertex potential of 1.4, 1.2, or 0.8 VRHE, respectively. All CV profiles were conducted at a scan rate of 2 mV/s in 0.05°M H2SO4. Based on the Quick-XANES data, the Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) was used to uncover the electrochemical reversibility behavior of iridium oxidation state as a function of metal loading and support material. Very interestingly, when the iridium loading is very high, a loss of the reversibility of the chemical state of Ir species on carbon and ATO are observed during the CV scan up to 1.6 VRHE, but not on TiO2 support material. In contrast, the chemical state of the Ir species was found to be highly reversible for low-loaded catalyst materials irrespective of the support material.In summary, our operando XAS investigations provide fundamental insights into the dynamic changes in electronic structure of Ir NPs depending on the support material and interparticle distance. Knowledge about the complex metal-support interactions and particle proximity effect can help to design more efficient and robust OER catalyst materials for PEM water electrolysis.Literature:[1] P. Mazúr, Int. J. Hydrog. Energ., 2012, 37, 12081-12088, DOI: 10.1016/j.ijhydene.2012.05.129[2] F. Bizotto, Catal. Sci & Tech., 2019, 9, 6345-6356, DOI: 10.1039/C9CY01728C[3] E. Oakton, ACS Catal., 2017, 7, 2346–2352, DOI: 10.1021/acscatal.6b032464] H. Tada, J. Phys. Chem. C., 2022, 126, 32, 13539–13547, DOI: 10.1021/acs.jpcc.2c03648[5] B. Hayden, Acc. Chem. Res., 2013, 46, 1858-1866, DOI: 10.1021/ar400001n

Activity and Stability of Iridium-Based Alloy Catalysts for PEM Electrolyzer

For large-scale production of green hydrogen via renewable energies, large capacities of highly performing, cost-effective water electrolyzers are needed. Polymer electrolyte electrolysis (PEMEL) operates at high current and pressure and is very compact compared to alkaline technology. However, it relies on very expensive noble catalysts such as Pt and Ir for H2 and O2 electrode, respectively. Meanwhile, unsupported Iridium black is considered as state-of-the-art in terms of corrosion stability and activity, whereas a lot of efforts aim at reducing loading by alloying or/and developing supported materials [1,2].In this work, Ir black and bi-metal Ir-M (M = Pt, Pd, Cr, Co) black catalysts were synthesized by co-reduction of iridium chloride and M-ion containing precursor in 0.1 M sodium borohydride at 180°C for 3 h under hydrothermal condition. The nominal mass ratio of Ir:M was fixed to 3:1. The structural characterization of the as-prepared catalysts was performed by means of XRD, TEM, Raman, and BET. Electrochemical activity of Ir-M black catalyst for OER was studied in deaerated 0.5 M H2SO4 electrolyte at room temperature by using a rotating disk electrode (RDE) cell. The total catalyst loading was about 200 μgIr cm-2. Additional cyclic voltammetry measurements over the potential range of -0.1–1.4 V vs. RHE at 40 mV s-1 were performed to identify redox behavior of the catalysts (fig. 1a). The accelerated degradation tests (ADT) were performed between 1.1 and 1.6 V at dE/dt=0.5 V s-1 with RDE at 1600 rpm for 1000 cycles. A commercial Ir-black catalyst purchased from Alfa Aesar was used as reference. Based on half-wave potential value at 30 mA cm-2 (fig. 1b), the following trend in lower overpotential for OER was obtained: Ir-Cr > Ir-Pt > Ir-Pd >> Ir-Co > Ir-black.PEMEL full cell experiments were performed in single cell with 5 cm² geometrical area in a balticFuelCells fixture at 60°C. The catalyst coated membrane (CCM) consists of 2 mgIr cm-2 anode and 1 mgIr cm-2 cathode coated on Nafion 117. Titanium felt and carbon paper were used as porous transport layers in the anode and cathode side, respectively. Accelerated stress tests (AST) were performed by using rectangular polarization signal to reflect dynamic electrolyzer operation. Thereby, the current density was varied between 0.05 and 3 A cm-2 in 10 s for at least 1000 h. After test, the cell components were post analyzed by SEM/EDX, XRD and XPS technique and anolyte/catholyte were analyzed by ICP-OES in order to evaluate the dissolved species. The electrochemical degradation performance of bi-metal alloy anode catalysts in PEMEL test will be presented as well.

Amorphous titanium dioxide with synergistic effect of nitrogen doping and oxygen vacancies by photoexcited sol-gel preparation for enhanced photodegradation of tetracycline

In this paper, a novel N-doped amorphous titanium dioxide (N20AT-hν) photocatalyst was prepared by the sol–gel route in which the sol added with salicylaldehyde hydrazone undergoes gel after photoexcitation. Based on a systematic exploration of as-prepared catalysts, it is known that N20AT-hν sample has a particle size of 50–60 nm, a specific surface area of 294.699 m2 g−1, and which is doped with nitrogen elements and forms abundant oxygen vacancies (OVs). The photocatalytic degradation rate of N20AT-hν for 20 mg L−1 tetracycline solution reached 92.23 % after 60 min, and the rate exhibited a slight decrease of 8.68 % after five cycles. Reactive species trapping experiments and electron spin resonance techniques indicate that superoxide radicals and holes are instrumental in photocatalytic degradation. Possible mechanism of forming the active species through OVs mediated traps and electron transfer pathways has been proposed. Furthermore, the predictive evaluations suggest that the degradation of tetracycline solutions by N20AT-hν sample results in less harmful decomposition product.Benefiting from the environmental friendliness of preparation method and the superiority of elemental doping, N20AT-hν material with synergistic effects has great potential for environmental applications.

Pyrolysis-Free Synthesis of Synergistic Single-Atom/Nanocluster Electrocatalysts for Hydrogen Evolution.

Constructing catalysts that simultaneously contain single atom/metal nanocluster active sites is a promising strategy to enhance the original catalytic behavior and accelerate the catalysis involving multi-electron reactions or multi-intermediates. Herein, the pyrolysis-free synthetic method is developed to integrate single atoms and nanoclusters towards highly satisfactory catalytic performances for both acidic and alkaline hydrogen electrocatalysis. The controllable pyrolysis-free strategy allows the precise modulation of the active centers, realizing the optimization of the adsorption energy and the regulation of the synergistic active components. Specially, the as-prepared catalysts with hybrid single-atom/nanocluster sites exhibited superior catalytic activities for hydrogen evolution in both acidic and alkaline media with low over-potentials at -10 mA cm-2 of 25 mV and 8.6 mV, respectively, combining with outstanding durability towards high current density and methanol poisoning. This work developed a universal synthetic strategy for the single atom/nanocluster synergy systems and addressed the superiority of hybrid single-atom/nanocluster sites.

Fluorine-doped cobalt ferrite integrated into 2D MXene with extended solar spectrum response and boosted charge separation for the removal of recalcitrant organic pollutants

In investigating sustainable methodologies for removing recalcitrant organic pollutants from wastewater, visible-light-responsive photocatalysis has drawn considerable interest. Therefore, intentionally engineered photocatalysts with enhanced solar-light-absorption capacity and boosted charge carrier’s separation are highly demanded. In the present attempt, pure cobalt ferrite (CoFe2O4) and its fluorine-doped counterpart (F-CoFe2O4) were fabricated via co-precipitation. The fluorine-doped material was integrated into the 2D MXene to design the composite (F-CoFe2O4@MXene) by the ultrasonication method. The structure, surface morphology, chemical composition, and optical properties of the as-prepared catalysts were characterized by various techniques, including powder XRD, FTIR, SEM, EDS, UV–vis absorption, and photoluminescence spectroscopy. The photocatalytic potential was estimated by degrading crystal violet (CV) dye and benzoic acid (BA), which were selected as model pollutants. The composite material showcases significantly enhanced catalytic efficiency relative to the pure and doped materials. Under solar light exposure for 140 min, 91 % (0.0138 min−1) and 87 % (0.0133 min−1) of CV and BA degradation were achieved, respectively. The remarkable catalytic potential of the composite material corresponds to the fluorine doping and integration to the 2D MXene, which has enhanced its visible-light absorption and lowered the rapid recombination rate of the separated charges (e-/h+). Systematic studies, including reaction kinetics, dominating catalytic species in photodegradation, and stability of the catalyst, were followed through to disclose the photocatalytic potential of the designed F-CoFe2O4@MXene. Furthermore, the real-time applicability of the catalyst has been explored.

Self-assembled 3D-flowers of CoS2-MoS2@NGA grown on graphene aerogel: As an emerging reliable electrocatalyst for hydrogen production in alkaline and acidic medium

The world is transitioning to more ecologically friendly and renewable energy sources, and hydrogen has enormous prospects for consumption in the future (2050). An electrochemical water-splitting (WS) is the most effective approach for separating pure hydrogen (H2) from water, however, the production rate depends on the catalyst activity. Recent strategies are focused on modifying the morphological structure, altering the metal edges, and increasing the active sites of catalysts to enhance their electrochemical performance. Herein, the solvothermal structural modification methods employed to achieve the 3D nanoflowers CoS2-MoS2@NGA, the cost-effective metal catalyst were grown on a graphene aerogel (GA) surface. The electrochemical accomplishments of the as-prepared catalyst were examined in the alkaline and acid medium to determine the optimal electrolyte. The CoS2-MoS2@NGA composite material achieved a noticeably low overpotential of 38 mV at a current density of 10 mA/cm2 and the fastest Tafel slope of 63 mV/dec towards the hydrogen evolution reaction (HER) compared to pure CoS2, MoS2, and N-doped GA (NGA). The composite exhibits an extraordinary specific surface area of 53.6 m2/g and an electrochemical active surface area (EASA) of 24.77 mF/cm2, contributing to its stability over 2000 CV cycles without significant activity loss. Overall, the composite materials achieved a comparatively high surface, low overpotentials, faster kinetics, a highly active electrochemical surface, and excellent long-term robustness. This work presents a promising approach for the elegant structural modification of non-noble metals, positioning CoS2-MoS2@NGA 3D flowers as an extremely efficient electrocatalyst for HER in an acidic medium.

Synchronous photocatalytic benzimidazole formation and olefin reduction by magnetic separable visible-light-driven Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 Nanocomposite

A visible light-responsive magnetically separable photocatalyst Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 is fabricated using vanillin as a natural junction under ultrasonic agitation. Structural, morphological, optical, thermal, and magnetic assessments of the as-prepared catalyst are carried out. The photocatalyst successfully drives the simultaneous benzimidazole formation, and olefin hydrogenation with high atom economy under blue LED light and mild conditions. The photocatalytic activity of Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 is significantly affected by the γ-Fe2O3:TiO2 weight ratio. PL spectra revealed the effective separation of carriers in the fabricated catalyst promoting its photocatalytic activity. The action spectra using the apparent quantum efficiency (AQE) exhibited the maximum AQEs at 520 and 750 nm in which the highest performance for styrene hydrogenation is observed. The title magnetically separable heterogeneous photocatalyst provides high yields of products under perfectly safe visible light, produces low/zero waste, and avoids using an external high-pressure hydrogen gas source, harmful solvents, undesirable additives, and reducing agents rendering green conditions for chemical reactions.

Alanine Production by Chemical Upcycling of Polylactic Acid Waste Over Fe-Doped Ru/CeO2.

Biodegradable polyesters, such as polylactic acid (PLA), is one of the most promising plastics with great potential to contribute to enabling a sustainable global circular economy. However, the efficient chemical upcycling of PLA plastic waste into high-value chemicals remains a grand challenge. Herein, a series of Ru/CeFeOx catalysts with varying Ru loadings were developed for the catalytic amination of PLA plastic waste to alanine in the presence of ammonia. The as-prepared catalysts exhibited exceptional catalytic activity, high selectivity, and excellent recyclability, achieving an alanine yield of 70.5 % at 180 °C for 18 h, significantly surpassing previous reports. The outstanding catalytic performance can be primarily attributed to the presence of Fe species in Ru/CeFeOx, which generated more oxygen vacancies, provided abundant base sites, and enhanced reducibility, therefore accelerating the reaction rate and enhancing catalytic efficiency. This study presents an alternative strategy for the sustainable chemical upcycling of PLA plastic waste into alanine and the realization of a circular economy.

Exploring Two-Dimensional MOF-Derived Co/Ni Species for Efficient Electrocatalytic Hydrogen Evolution Reaction

Hydrogen evolution reaction (HER) has received a lot of attention due to its promising advantages in producing “green hydrogen” via electrocatalysis with low cost and high efficiency. Until now, developing transition metal-based electrocatalysts for HER has been a great challenge. In this regard, we reported a facile strategy to fabricate Co/Ni species encapsulated by carbon structure (CoNi@C) through annealing two-dimensional (2D) metal-organic framework (MOF) nanosheets. The CoNi@C that was prepared under 600 °C achieved the highest catalytic performance in 1.0 M KOH electrolyte with an overpotential of 330 mV to acquire 100 mA cm−2. In addition, the effect of KOH concentrations on the HER performance of CoNi@C-600 was explored. In 3.0 M KOH electrolyte, the current density of 100 mA cm−2 has been attained at a bias potential of 80 mV. The alkaline environment can improve the electrocatalytic performance and further enhance the stability of the as-prepared catalysts. This work would endow promising opportunities for manipulating MOF-based structures through pyrolysis to fabricate highly efficient electrocatalysts.

Preparation of ultra-sensitive and selective hydrogen peroxide-based colorimetric sensor using highly exfoliated g-C3N4 nanosheets with peroxidase-like activity.

Ahighly sensitive, portable, rapid, and accurate colorimetricsensing method is presented.It isbased upon exfoliated g-C3N4 nanosheets (E-g-C3N4 NSs), having peroxidase nanozyme-like properties. The as-prepared catalyst (E-g-C3N4 NSs) tends to oxidize the colorless tetramethyl-benzidine (TMB) into oxidized-TMB in the presence of hydrogen peroxide (H2O2) generating adark blue color and corresponding ultraviolet visible-spectral changes following aMichaelis-Menten kinetic. The prepared colorimetric sensor exhibited response within the range 0.001-0.450μM having R2 value of 0.999 and adetective limit (LOD) of 0.15 ± 0.04nM. Furthermore, the sensor also displayed outstanding selectivity, ample stability (10weeks), and excellent practicability in real sample applications. All these outstanding properties were highly attributed to the large surface area with exposed actives sites, high surface energy, and large conductive structure of E-g-C3N4 NSs. For comparison of thecatalytic study, we have also explored the sensing mechanism of B-g-C3N4, using thesame optimized experimental conditions. Resultantly, we concluded that the proposed sensor (E-g-C3N4 NSs) will gain considerable attention for on-site environmental and health monitoring in future endeavor.

Iron phosphides nanoparticles strongly coupled to N-doped carbon for high-efficiency oxygen reduction and evolution

Constructing composite structures is an effective strategy for tailoring the electronic configuration and balances the adsorption/desorption capability of oxygen-containing intermediates for obtaining high-performance bifunctional catalysts. Herein, an in-situ pyrolysis strategy was used to construct Fe2P nanoparticles supported on N-doped carbon (Fe2P/NC) catalyst. The DFT indicated that the catalytic activity of the as-prepared catalyst is significantly increased by the strong electronic interaction between the Fe2P nanoparticles and the nitrogen-doped carbon, which endows the catalyst with fast electron transfer capability and optimizes the free energy between the catalyst and the adsorbed intermediate, as well as the d-band center of the material. The as-synthesized Fe2P/NC has a low potential gap ΔE (ΔE = Ej=10 – E1/2) of ca. 0.75 V, a specific capacity as high as 833 mAh·gZn−1 and cycling stability for 1320 cycles at the current density of 10 mA·cm−2. Such a synthesis strategy provides an effective route to realizing applications for portable electronic Zn-air battery-related devices.

Construction of Spatially Separated Acid-Base Sites inside and outside Metal-Organic Framework Nanocrystals for Efficient Cascade Reactions.

The development of acid-base catalysts for one-pot cascade reactions remains challenging because of the inherent incompatibility of inorganic acid and base active sites. Here, we introduced an innovative approach that employs spatial separation to construct separated inorganic acid-base sites, achieving sequence control of acid-base cascade reactions. The as-prepared bifunctional catalyst applied metal-organic framework (MOF) nanocrystals as spatial separators, with the inside microcavities loaded with 1 nm inorganic polyoxometalate acid H3PMo12O40 clusters (NENU-5) and the outside crystal surface covered with basic CuCo layered double hydroxide (CuCo-LDH) nanosheets. By applying the resultant NENU-5@CuCo-LDH catalyst to cascade deacetalization-Knoevenagel condensation, over 99% of the benzaldehyde dimethyl acetal (BDMA) was transformed into the final benzylidene cyanoacetate (BCA) with a 99% yield at 80 °C and solvent-free conditions. Compared to the random NENU-5+CuCo-LDH, the NENU-5@CuCo-LDH with spatially separated acid-base sites indicated a higher reaction rate due to the designed reaction sequence and the shorter mass transfer pathway. Moreover, this hierarchical structure showed inherent shape selectivity and extraordinary stability. This study introduces spatial separation to address the incompatibility issue between inorganic acid and base active sites, offering novel perspectives for acid-base systems.

Construction of engineered heterojunction based on CdS and MgO material co-integrated into a flat plane-like graphene for tetracycline decontamination: Ecological hazard assessment and toxicity alleviation

This study encompasses the photocatalytic decomposition activity of an appreciable ternary CdS/MgO/graphene heterostructured composite (denoted as CMG) for the decontamination of recalcitrant tetracycline (TTC) from aqueous environment under LED light illumination. The physicochemical characteristics of the as-prepared catalysts were elucidated utilizing a series of advanced analytical methods including XRD, FTIR, DRS, BET, EIS, TEM, and FESEM. The CMG architectures reveal vigorous photocatalytic performance towards the decontamination of TTC upon exposure to the LED light, the decontamination rate is approximately 5.5, 4 and 3 times higher than neat graphene, MgO and CdS, respectively. Under the optimized conditions (i.e., pH: 7, CMG dosage: 0.5 g. L−1, light intensity: 75 W and TTC content: 30 mg. L−1), the remarkable degradation rate of TTC (98 % in 120 min) was achieved by the CMG/LED system. An inhibitory impact of anions during the photocatalyst process was recorded as follows: Cl− > NO3− > SO42− > PO43−. To provide a comprehensive understanding of the photocatalyst's behavior and shed light on its mechanism, various analytical techniques were utilized including band structure evaluation, EIS, and capture experiments. The active agents trapping experiments evidenced that OH radicals are the predominant decomposing agents participated in the TTC decontamination. Furthermore, the CMG composite exhibited a noticeable performance during six cycling treatment experiments, inducing its remarkable capability for practical applications. The photocatalytic mechanism of the TTC degradation route over the CMG/LED system was unraveled on the basis of the LC-MS analysis. The ECOSAR software calculations forecasted that CMG/LED system could be regarded as an ecologically benign technology to eliminate antibiotic-related hazards to the living individuals and the environment. In extension, the ecological risk assessment of TTC and its intermediates was scrutinized over CMG/LED system for the first time ever, revealing the excellent performance of the target system in diminishing the actual potential ecological risk.

Enhanced ammonia yield rate from nitrogen on collapsed dodecahedral-shaped Co/NC electrocatalyst

Nowadays, multi-component non-precious metal catalysts have been considered as a significant strategy for enhancing the yield of synthesizing NH3 by electrocatalytic nitrogen reduction reaction (E-NRR). In the present work, carbon composites doped with well-dispersed Co and N (Co/NC) were prepared by pyrolyzing zeolitic imidazolate framework-67 (ZIF-67) at various temperatures protected under a N2 flow. Co/NC exhibits a collapsed dodecahedral morphology with a mesoporous structure (3.5–4 nm). The chemical states of Co/N and the structural defects of C are closely related to the carbonization temperature. In a N2-saturated 0.1 M KOH electrolyte, the as-prepared catalysts exhibit an NH3 yield rate (Y(NH3)) of 60.57 μg h-1 mgcat.-1 and a Faradaic efficiency (FE) of 23.3 % at -0.1 V (vs the reversible hydrogen electrode, RHE) at ambient conditions. The enhanced E-NRR activity of Co/NC may primarily originate from an associative distal pathway on the Co-N3C sites and the carbon defects in an alkaline electrolyte. Specifically, this work presents a three-component E-NRR catalyst with excellent stability and great activity based on Co/NC.

Cu/N-doped carbon spheres derived from soybean flour as an active green nanocomposite for the synthesis of 1,4-disubstituted 1H-1,2,3-triazole derivatives

Cu immobilized onto N-doped carbon spheres (Cu/N-doped CS) derived from soybean flour was synthesized via the hydrothermal method and certified as a green high-efficiency catalyst for the regioselective synthesis of 1,4-disubstituted 1H-1,2,3-triazoles. The obtained N-doped carbon spheres from a combination of glucose and soy flour have a larger size and suitable affinity for load copper species. The morphology and structure of the as-prepared catalyst have been confirmed based on FT-IR, XRD, FE-SEM, EDX, BET, and ICP-OES characterizations. The catalytic performance of the Cu/N-doped carbon spheroids was investigated experimentally. It was found that the Cu/N-doped CS nanocomposite has a high efficiency and recyclability for 5 cycles without any appreciable loss in its catalytic activity in the synthesis of 1,4-disubstituted 1H-1,2,3-triazoles via the three-component condensation reaction of various epoxide/alkyl or aryl halides, sodium azide, and phenylacetylene in a water medium. Furthermore, significant advantages such as stability, ease of preparation, low cost of the carbon resource, high regioselectivity, and good product yield have been achieved in the heterogeneous catalyst system attractive for large-scale in many industrial products.

In Situ Growth of MoN on Nickel Foam for Highly Efficient Hydrogen Evolution in Alkaline Solution.

Highly efficient, stable, and low-cost hydrogen evolution catalysts are urgently required for water electrolysis. Herein, a method for in situ growth of medium-nitrogen nanosheet MoN catalysts with a large electrochemical surface area on nickel foam (NF) is proposed. The results show that the morphology of the as-prepared catalysts greatly depends on the nitrogen sources and nitridation temperature. The MoN/NF catalyst nitride at 700 °C using melamine as a nitrogen source exhibits a spindle-like morphology consisting of stacked nanosheets, which is conducive to exposing more active sites, thereby increasing the catalyst activity. The N atoms in MoN could adjust the chemical environment of the metal by changing the density of the d-band electron state, which further improves the HER performance. Benefiting from the regulation of Mo charge distribution and exposure to more active sites through N doping and morphological control, the MoN/NF catalyst exhibits superior HER performance with an overpotential of 70 mV at a current density of 10 mA·cm-2, a Tafel slope of 44.3 mV dec-1, and an Rct of 1.83 Ω, indicating high HER catalytic activity, fast kinetics, and excellent conductivity. Theoretical calculations reveal that among the (002), (202), and (200) planes of MoN, the (202) plane exhibits the lowest value of |ΔGH*| (0.47 eV), which is close to that of Pt(111) (0.14 eV). More importantly, MoN(202) also has the smallest work function of 3.58 eV, indicating an enhanced capability to offer electrons. This work develops a strategy to design high-performance and low-cost transition-metal nitride HER catalysts.

Surface in situ Co-Mn modification over LaMnO3 perovskite with enhanced activity for ethane combustion

Catalytic combustion is one of effective ways to remove short-chain alkanes. In this study, we elaborately designed a novel catalyst of in situ Co-Mn decorated LaMnO3 perovskite for ethane catalytic combustion, in which extra Mn and Co species were introduced via acidic KMnO4 and Co(NO3)2 solution precipitation method. The addition of Mn and Co could not only slightly etch LaMnO3, thereby increasing specific surface area and redox property, but also generate new active phase CoMn2O4, thus accelerating reaction. Among all the as-prepared catalysts, CMO/LMO-0.5 exhibited admirable ethane removal efficiency with a T90 of 365 °C, a reaction rate of 0.46 mmol·g−1·h−1, a TOF value of 0.64 mmol·g−1·h−1, and excellent hydrothermal stability and reusability. Moreover, according to in situ DRIFTS, a possible pathway was proposed. This work can rationalize an alternative approach to develop an active catalyst for short-chain alkanes catalytic combustion or other catalytic systems.