Performance Of Catalysts Research Articles

Pd-CQDs/CdS ternary composite for highly efficient visible light driven H2 evolution under combined action of type I heterojunctions and Schottky junctions

Visible light driven catalytic hydrogen production over CdS based catalysts could be a good candidate strategy to help solve the global energy crisis. To improve the photocatalytic H2 production activity of CdS, the series of Pd nanoparticles and carbon quantum dots (CQDs) co-modified CdS nanorods (NRs) composites were designed to simultaneously build the type I heterojunctions and Schottky junctions. The photocatalytic H2 evolution activities of the samples were assessed under visible light (λ > 420 nm) irradiation and the reaction mechanism was proposed. The Pd-0.35CQDs/CdS catalyst exhibited excellent activity with the average hydrogen evolution rate (HER) of 47.1 mmol h−1 g−1, which is 36.2 times higher than that of the pure CdS. Its apparent quantum efficiency is 17.1% (450 nm light). The combined action of Schottky junctions and type I heterojunctions in the composite Pd-0.35CQDs/CdS greatly promoted charge transfer and separation, resulting in enhancement of the photocatalytic activity. Additionally, the synergistic effect of the Pd nanoparticles and CQDs resulted in enhanced visible light absorption and optimized band structure, helpful to enhancement of the photocatalytic activity. This study provides a simple and cost-effective strategy for improving visible light catalytic H2 production performance of catalysts.

Construction of Ru-doped Co nanoparticles loaded on carbon nanosheets in-situ grown on carbon nanofibers as self-supported catalysts for efficient hydrogen evolution reaction

Exploring efficient and economical electrocatalysts to replace noble metal electrocatalysts has become a major research focus nowadays. In this paper, Ru-doped Co nanoparticles loaded on carbon nanosheet (CNS) in-situ grown on carbon nanofibers (Ru–Co@CNS/CNFs) were constructed as a self-supporting working electrode for high-efficiency hydrogen evolution. The prepared Ru–Co@CNS/CNFs possessed excellent catalytic activity with only 78 mV overpotential at 10 mA cm−2 current density and good stability with only 102 mV voltage attenuation at 100 mA cm−2 current density for 100 h continuous operation. The excellent catalytic performance could be attributed to the unique microstructure of the nanosheets in-situ grown on the nanofibers, it resulted in a higher Co surface density of 1.28 mg cm−2, indicating more loading of metal to improve catalytic activity of HER, and the formed Ru-doped Co nanoparticles could be evenly distributed on the carbon nanosheets to prevent the aggregation of nanoparticles, which could expose more active sites. Additionally, the density functional theory (DFT) calculations revealed Ru doping could accelerate the dissociation of water, optimize the adsorption energy of hydrogen intermediates and improve the kinetics of the HER reaction. This work provides a new approach to reduce the use of noble metals while improving the catalytic performance of catalysts.

Lattice Strain in High Entropy Oxides Promote CO2 Photomethanation.

Lattice strain is widely investigated to improve the performance of heterogeneous catalysts, however, the effect of lattice strain is under-explored in high-entropy oxide based photocatalyst. In this study, noble-metal-free (CoCrMnFeNi)Ox with lattice strain is synthesized using a temperature-controlled, template-free and salt-assisted strategy. In the presence of lattice strain, an intensive internal electric field is formed in (CoCrMnFeNi)Ox, promoting the separation of photoinduced charge carriers. The size of the (CoCrMnFeNi)Ox can be tuned by varying the calcination temperature. Specifically, (CoCrMnFeNi)Ox prepared at a higher temperature possesses a smaller grain size exposing more active sites, resulting in an enhanced CO2 photomethanation performance. This work provides valuable insights for the rational design of the photocatalysts and highlights the promising role of high-entropy oxides in heterogeneous photocatalysis.

Employing Ammonia for the Synthesis of Primary Amines: Recent Achievements over Heterogeneous Catalysts.

Primary amines represent highly privileged chemicals for synthesis of polymers, pharmaceuticals, agrochemicals, coatings, etc. Consequently, the development of efficient and green methodologies for the production of primary amines are of great importance in chemical industry. Owing to the advantages of low cost and ease in availability, ammonia is considered as a feasible nitrogen source for synthesis of N-containing compounds. Thus, the efficient transformation of ammonia into primary amines has received much attention. In this review, the commonly applied synthetic routes to produce primary amines from ammonia were summarized, including the reductive amination of carbonyl compounds, the hydrogen transfer amination of alcohols, the hydroamination of olefins and the arylation with ammonia, in which the catalytic performance of the recent heterogeneous catalysts is discussed. Additionally, various strategies to modulate the surface properties of catalysts are outlined in conjunction with the analysis of reaction mechanism. Particularly, the amination of the biomass-derived substrates is highlighted, which could provide competitive advantages in chemical industry and stimulate the development of sustainable catalysis in the future. Ultimately, perspectives into the challenges and opportunities for synthesis of primary amines with ammonia as N-resource are discussed.

The improvement of heat transfer using Co/SiO2 spiral structured catalyst for green diesel production by Fischer–Tropsch synthesis

In this study, the improvement of heat transfer was applied to eliminate hotspots of a highly exothermic reaction, Fischer–Tropsch synthesis (FTS), by means of two facile methods: (I) adding high thermal conductive materials media diluted in catalysts (SiC and Al chips), and (II) using structured reactors equipped with well-designed structured catalysts with advantages of heat dissipation/removal. The 20%Co/SiO2 catalyst powder prepared by simple impregnation was employed for constructing structured catalysts and granular packed bed catalysts. The structured catalyst was prepared by coating method of Co/SiO2 slurry on an aluminum spiral and plate substrate. The catalytic performance of as-prepared catalysts was then tested for FTS in a fixed-bed reactor at 210–230 °C, 20 bar. Both gaseous and liquid products were collected and analyzed. The heat transfer improvement of packed bed catalytic system and structured catalytic system were compared and discussed. As a result, the structured catalytic system with spiral structured catalyst can provide the best improvement of heat/mass transfer, resulting in enhanced diesel selectivity, though the oil production rate was unsatisfactory. Meanwhile, among the packed bed catalytic systems, SiC media possessed the best heat removal material, producing the highest oil yield. In addition, the fresh and spent catalysts were analyzed by several techniques including TEM, SEM, XRD, BET, ICP-OES, H2–TPR, and TGA to relate the physicochemical properties of the prepared catalysts and its FTS performance.

Isolated Pt Atoms Stabilized by Ga2O3 Clusters Confined in ZSM-5 for Nonoxidative Activation of Ethane.

Selective activation of light alkanes is an essential reaction in the petrochemical industry for producing commodity chemicals, such as light olefins and aromatics. Because of the much higher intrinsic activities of noble metals in comparison to non-noble metals, it is desirable to employ solid catalysts with low noble metal loadings to reduce the cost of catalysts. Herein, we report the introduction of a tiny amount of Pt (at levels of hundreds of ppm) as a promoter of the Ga2O3 clusters encapsulated in ZSM-5 zeolite, which leads to ∼20-fold improvement in the activity for ethane dehydrogenation reaction. A combination of experimental and theoretical studies shows that the isolated Pt atoms stabilized by small Ga2O3 clusters are the active sites for activating the inert C-H bonds in ethane. The synergy of atomically dispersed Pt and Ga2O3 clusters confined in the 10MR channels of ZSM-5 can serve as a bifunctional catalyst for the direct ethane-benzene coupling reaction for the production of ethylbenzene, surpassing the performances of the counterpart catalysts made with PtGa nanoclusters and nanoparticles.

Strain engineering of CoSA[sbnd]N[sbnd]C catalyst toward enhancing the oxygen reduction reaction activity

Developing efficient and cost-effective platinum-group metal-free (PGMF) catalysts for the oxygen reduction reaction (ORR) is crucial for energy conversion and storage devices. Among these catalysts, metal-nitrogen-carbon (MNC) materials, particularly cobalt single-atom catalysts (CoSANC), show promise as ORR electrocatalysts. However, their ORR activity is often hindered by strong hydroxyl (OH) adsorption on the Co sites. While the impact of strain engineering on MNC electrocatalysts has been minimally explored, recent studies suggest its potential to enhance catalytic performance and optimize intrinsic activity in traditional bulk catalysts. In this context, we investigate the effect of surface strain on CoSANC for ORR activity and correlate substrate-strain-induced geometric distortions with catalytic activity using experimental and theoretical methods. The findings suggest that the d-band center gap of spin states (Δεd) may be a preferred descriptor for predicting strain-dependent ORR performance in MNC catalysts. Leveraging CoSANC moiety placed on a substrate with an average size of 1.0 μm, we achieve performance comparable to that of commercial Pt/C catalysts when used as a cathode catalyst in zinc-air batteries. This investigation unveils the structure–function relationship of MNC electrocatalysts regarding strain engineering and provides valuable insights for future ORR activity design and enhancement.

Promoting effect of Cu as electron transfer medium on NH3-SCO reaction in asymmetric Ag-Ov-Ti-Sm-Cu ring active site

Selective catalytic oxidation of ammonia (NH3-SCO) has become an effective method to reduce ammonia (NH3) emissions, and is a key part to solve the problem of NH3 pollution. Nevertheless, the optimization of this technology’s performance relies heavily on innovation and the development of catalyst design. In this study, a SmCuAgTiOx catalyst with an asymmetric Ag-Ov-Ti-Sm-Cu ring active site was prepared and applied to the NH3-SCO reaction. The low conversion of Cu-based catalysts in NH3 at low temperature and the inherent low N₂ selectivity of Ag-based catalysts were solved. The successful creation of the asymmetric ring active site improved the catalyst’s reduction performance. Additionally, Cu, acting as an electron transfer medium, plays a crucial role in enhancing electron transfer within the asymmetric ring active site, thus increasing the redox cycle of the catalyst during the reaction. In addition, some lattice oxygen is lost in the catalyst, resulting in the formation of a large number of oxygen vacancies. This process stimulates the adsorption and activation of surface-adsorbed oxygen, facilitating the conversion of NH3 to an amide (NH2) intermediate during the reaction and reducing non-selective oxidation. The N2 selectivity was improved without significantly affecting the performance of Ag-based catalyst. In-situ diffuse reflectance fourier transform infrared spectroscopy (In-situ DRIFTS) analysis reveals that the SmCuAgTiOx catalyst primarily follows an “internal” selective catalytic reduction (iSCR) mechanism in the NH3-SCO reaction, complemented by the imide mechanism. The asymmetric Ag-Ov-Ti-Sm-Cu ring active site developed in this study provides a new perspective for efficiently solving NH3 pollution in the future.

Study on the performance of Co–Ni sulfide electrocatalysts supported by different fibroin-based carbon precursors

Research on sustainable energy sources is crucial for alleviating environmental issues and addressing energy security concerns. This study investigates the utilization of various silk precursors in the hydrogen evolution reaction. Waste silk fabric, regenerated silk fibroin film, porous silk fibroin, silk cocoon and degummed silk fibroin were used as precursors to prepare HER electrocatalysts. To investigate the influence of precursor form on catalytic perform9ance, a comparative analysis of the morphology, structure and composition of different materials was conducted. Among various catalysts, waste silk fabric based catalysts exhibit the most excellent catalytic activity, with an overpotential of 113 mV at 10 mA cm−2 and a Tafel slope of 30.9 mV/dec. Even After 1000 cycles of testing, it still maintains excellent catalytic activity. This study provides insights into the influence of precursor forms on the electrochemical performance of biomass carbon-based catalysts, aiming to inspire further research in this field.

Engineering Oxygen Vacancies of Co-Mn-Ni-Fe-Al High-Entropy Spinel Oxides by Adjusting Co Content for Enhanced Catalytic Combustion of Propane.

Transition metal-based oxides with similar oxidation activities for catalytic hydrocarbon combustion have attracted much attention. In this study, a new class of metal high-entropy oxides (CoxMnNiFeAl)3O4 (x = 1, 2, 3, 4, 5) with a porous structure was fabricated through a simple and inexpensive NaCl template-assisted sol-gel approach, which was employed for the catalytic oxidation of propane. The results indicated that the content of cobalt has a great impact on its activity, and the (Co4MnNiFeAl)3O4 catalyst exhibited the best catalytic activity. At the high space velocity of 60 000 mL·g-1·h-1, the optimized one with high-temperature treatment can still achieve 90% propane conversion at 309 °C, which is 68 and 178 °C lower than those of the (CoMnNiFeAl)3O4 catalyst and pure cobalt oxide, respectively. Meanwhile, it has the lowest apparent activation energy (46.6 KJ·mol-1) and the fastest reaction rate (26.976 × 10-6 mol·gcat-1·s-1 at 290 °C). The improved performance of the (Co4MnNiFeAl)3O4 catalyst could be attributed to the enhancement of low-temperature reducibility, the increased number of reactive surface oxygen species, and the cocktail effect of the high-entropy oxides. This work provides new insights into the preparation of efficient light alkane degradation catalysts and a realistic approach for the large-scale application of high-entropy oxides in the field of oxidation catalysts.

Nest-shaped hollow-encapsulated Pd catalyst enhances the catalytic performance of hydrogen peroxide directly synthesizing from hydrogen and oxygen

A well-defined structural morphology can significantly construct a special catalytic micro-reaction environment to enhance the catalytic performance of Pd catalyst in the direct synthesis of hydrogen peroxide from hydrogen and oxygen (DSHP). In this study, SiO2 was used as a rigid template, PdCl2 as the Pd precursor, and dopamine hydrochloride (DA) as the carbon and nitrogen source to synthesize a nest-shaped hollow-encapsulated Pd catalyst named PdMulti@ONHCS. This catalyst was successfully constructed via high-temperature pyrolysis of poly dimethyl diallyl ammonium chloride (PDDA), which generated a blasting effect crucial for this formation. Characterization analysis, catalytic performance evaluation experiment, and molecular dynamics simulation were conducted to explore the structure-performance relationship of PdMulti@ONHCS catalyst in DSHP. Both experimental and simulation results consistently showed that the nest-shaped hollow structure of PdMulti@ONHCS catalyst created a distinctive catalytic microreactor environment with a spatial mass transfer constraint, which was not only conducive to adsorption and enrichment of H2 and O2 at Pd active sites to produce H2O2. In addition, the generated H2O2 can be desorbed from Pd active sites in time and rapidly diffused into the reaction solution, effectively inhibiting the dissociation of species containing OO bonds on the Pd surface, resulting in severe hydrogenation and decomposition side reactions, and improving H2O2 productivity and selectivity.

Oligomerization of ethylene by dinuclear chromium catalysts bearing phenyl-bridged bifunctional imine-pyrrolide/thiophene ligands

Dinuclear chromium(III) complexes [Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl2]2 (Z= C4H3N, L1-Cr2) or [Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl3]2 (Z = C4H3S, L2-Cr2; Z = 5-methyl-C4H2S, L3-Cr2; Z = 5-phenyl-C4H2S, L4-Cr2) were synthesized by reaction of the phenyl-bridged bifunctional imine-pyrrole/thiophene ligands with [CrCl3(THF)3]. DFT calculations for L2-Cr2 revealed that both isomers (anti and syn) are stable presumably due to the nonrigid skeleton of this class of ligands. On activation with MAO, all chromium complexes showed catalytic activity in ethylene oligomerization, providing a non-selective distribution of α-olefins (C4-C12+) together with varying amounts of polymer (3.6 – 45.0 wt%). The nature of the pendant heterocyclic moieties plays a substantial influence on the catalytic performances of these binuclear Cr catalysts. L1-Cr2 bearing pyrrolide unit yielded a significant quantity of polymer (45.0 wt%) while the binuclear chromium complexes based on thiophene unit showed higher productivities towards production of oligomers (up to 94.4 wt%). These latter Cr complexes showed higher productivities in comparison to their mononuclear analogues. DFT calculations, assuming the formation of cationic chromium (III) species after treatment with MAO in ethylene atmosphere, suggested the coordination of the thiophene group to the chromium metal center, and thus influencing the catalytic performance of L2Cr2– L4-Cr2. By adjusting the reaction conditions, L3-Cr2 showed TOF of 131,100 mol ethylene·mol Cr−1·h−1 producing predominantly oligomers (89.3 wt% of total products) with high selectivity for α-olefins (>91.5 wt%).

Impact of various metal promoters on the propane dehydrogenation performance of cobalt-based catalysts

Large-scale exploitation of natural gas and shale gas has spurred the development of the propane dehydrogenation technology. While cobalt-based catalysts, known for their low cost and low toxicity, effectively activate C–H bonds, they are often deactivated because of coke formation. In this study, we prepared SBA-15 molecular sieves using a hydrothermal synthesis method and developed a series of Co-based catalysts supported on SBA-15 with various metal promoters (denoted Co-X/SBA-15, where X = Mn, Fe, Mg, Zn, or La) via an incipient wetness impregnation method. Characterization techniques and activity evaluation results revealed that the Co–O–Mg structure in the Co-Mg/SBA-15 catalyst stabilizes the primary Co2+ active site and hinders the reduction of the CoOx species. The incorporation of Mg enhances the total alkalinity of the catalyst, facilitating propane adsorption and propylene desorption, leading to superior activity and stability. Although the addition of La improved propylene selectivity, it did not significantly enhance propane conversion. Conversely, the introduction of Mn, Fe, and Zn into the catalyst inhibited the reaction.

Impact of lanthanum ion exchange and steaming dealumination on middle distillate production using nanosized Y zeolite catalysts in hydrocracking reactions.

In the field of hydrocracking reactions, achieving optimal middle distillate yields remains a persistent challenge with commercially available zeolite Y catalysts. This limitation is attributed to challenges related to diffusion constraints within the catalyst. In response, we present a promising solution not only to these problems but also to the challenges encountered in nanosized Y zeolites when attempting to generate acidic sites within their structure and when analyzing their performance in vacuum gas oil hydrocracking. NiMo catalysts based on nanosized Y zeolites with different crystal sizes exchanged with lanthanum, effectively address diffusion issues and significantly enhance catalyst performance compared to dealuminated nanosized and commercial Y zeolite under the same reaction conditions. The catalysts were characterized by TGA, ICP-OES, XPS, N2 physisorption, FT-IR for pyridine acidity, TEM-mapping, and the 3-methyl thiophene reaction to test the hydrogenating capacity. Surface analysis and microscopy showed greater porosity in the catalysts with smaller zeolites and different arrangements of their components. The catalysts based on steamed protonated nanosized Y zeolites with a larger size and lanthanide nanosized Y zeolite with a smaller size yielded more middle distillates. Research provides a comprehensive analysis, providing a correlation between the catalytic performance and the size of the nanosized Y zeolite.

Novel Insight into the Synergistic Mechanism for Pd and Rh Promoting the Hydro-Defluorination of 4-Fluorophenol over Bimetallic Rh-Pd/C Catalysts.

This study explores the synergistic effect between the Rh and Pd of bimetallic Rh-Pd/C catalysts for the catalytic hydro-defluorination (HDF) of 4-fluorophenol (4-FP). It was found that 4-FP could not be efficiently hydro-defluorinated over 6% Pd/C and 6% Rh/C due to the inherent properties of Pd and Rh species in the dissociation of H2 and the activation of C-F bonds. Compared with 6% Pd/C and 6% Rh/C, bimetallic Rh-Pd/C catalysts, especially 1% Rh-5% Pd/C, exhibited much higher catalytic activity in the HDF of 4-FP, suggesting that the synergistic effect between the Rh and Pd of the catalyst was much more positive. Catalyst characterizations (BET, XRD, TEM, and XPS) were introduced to clarify the mechanism for the synergistic effect between the Rh and Pd of the catalyst in the HDF reaction and revealed that it was mainly attributed to the bifunctional mechanism: Pd species were favorable for the dissociation of H2, and Rh species were beneficial to the activation of C-F bonds in the HDF reaction. Meanwhile, the interaction between Rh and Pd species enabled Rh and Pd to exhibit a more positive synergistic effect, which promoted the migration of atomic H* from Pd to Rh species and thus enhanced the HDF of 4-FP. Furthermore, 1% Rh-5% Pd/C prepared using 20-40 equiv NaBH4 exhibited the best performance in the catalytic HDF of 4-FP. Catalysis characterizations suggested that appropriate Rh3+/Rh0 and Pd2+/Pd0 ratios were beneficial to the dissociation of H2 and the activation of C-F bonds, which caused the more positive synergistic effect between the Rh and Pd of Rh-Pd/C in the HDF reaction. This work offers a valuable strategy for enhancing the performance of catalytic HDF catalysts via promoting synergistic effects.

Universal Predictive Power: Introducing the Electronic Structure Decomposition Approach for CO Adsorption and Activation on Al2O3-Supported Ru Nanoparticles.

Accurate prediction of catalyst performance is crucial for designing materials with specific catalytic functions. While the density functional theory (DFT) method is widely used for its accuracy, modeling heterogeneous systems, especially supported transition metals, poses significant computational challenges. To address these challenges, we introduce the Electronic Structure Decomposition Approach (ESDA), a novel method that identifies specific density of states (DOS) areas responsible for adsorbate interaction and activation on the catalyst. As a case study, we investigate the influence of α-Al2O3(0001) as a support material on CO adsorption energy and the stretching frequency of the C-O bond on Ru nanoparticles (NPs). Using multiple linear regression analysis, ESDA models were trained with data from isolated Ru NPs and adjusted using supported NP sample data. The ESDA models accurately predict the CO adsorption energies and C-O vibrational frequencies, demonstrating strong linear correlations between predicted and DFT-calculated values with low errors across various adsorption sites for both isolated and supported Ru NPs. Beyond pinpointing the DOS areas responsible for CO adsorption and C-O bond activation, this study provides insights into manipulating these DOS areas to control CO activation, hence facilitating CO dissociation. Additionally, ESDA significantly accelerates the characterization and prediction of CO adsorption and activation on both isolated and supported Ru NPs compared to DFT calculations, expediting the design of new catalytic materials and advancing catalysis research. Furthermore, ESDA's reliance on the electronic structure as a descriptor suggests its potential for predicting various properties beyond catalysis, broadening its applicability across diverse scientific domains.

Synthesis of Pt-doped CoFe layered double hydroxide derived from zeolitic imidazolate framework for efficient electrochemical oxygen evolution reaction

Zeolitic imidazolate frameworks (ZIFs), a class of promising metal organic frameworks (MOFs) material, display high porosity and chemical/thermal stability. However, there are problems such as few active sites and restricted exposed active areas, which limit the oxygen evolution reaction (OER) performance of catalysts. Here, starting from zeolitic imidazolate framework-67 (ZIF-67), we have successfully synthesized Pt-doped CoFe layered double hydroxide (Pt/CoFe LDH) catalysts for efficient OER catalysis. The obtained Pt/CoFe LDH-4 catalysts provides large surface areas and abundant active sites, which further improves the OER performance. In detail, the Pt/CoFe LDH-4 exhibits a lower overpotential of 263 mV at a current density of 40 mA cm−2, in 1 M KOH solution, the stability of the catalyst exceeds 120 h at this current density, far superior to commercial catalyst RuO2. This study describes a new design idea for synthesis of LDH catalytic materials with low noble metal doping, which broadens the way to the synthesis of robust OER catalysts derived from ZIF-67.

Fabrication of Z-scheme Fe2O3/g-C3N4 nanocomposite with improved visible light induced photodegradation of pharmaceutical pollutants and photoelectrochemical water oxidation

The photodegradation and photoelectrochemical performance of Fe2O3 catalyst is an encouraging visible-light induced catalyst owing to its less harmfulness, cheap and ecofriendly. However, owing to its quick charge carriers recombination rate and less lifespan of charge carriers obstructs its catalyst application. Therefore, it has been lately established that the construction of heterojunction with other semiconductor might be a possible method to improve its catalytic activity. Herein, a novel Z-scheme Fe2O3/g-C3N4 heterostructure catalyst has been synthesized by a simple hydrothermal technique and studied its photoelectrochemical and photodegradation activity. The addition of g-C3N4 greatly improves the light absorption ability light, reduced charge recombination rate and progress the charge transportation. The composite catalyst exhibited the superior photodegradation performance (97.8 %) of sulfamethoxazole antibiotic remedy within 30 min of visible light illumination. •OH and •O2– radicals show a key role for dye degradation activity, and proposed a possible photodegradation charge carrier transfer mechanism based on a potential band structures of composite catalyst. Furthermore, the prepared catalysts are further used to examine the photoelectrochemical properties for hydrogen generation. The Fe2O3/g-C3N4 nanocomposite photoelectrode exhibited enriched photocurrent density (0.764 mA/cm2) than g-C3N4 (0.271 mA/cm2) and Fe2O3 (0.370 mA/cm2) photoelectrodes, which ∼ 2.8 and ∼2.1 folds greater photocurrent density than pure photoelectrodes. Electrochemical impedance spectroscopy analysis revealed that the composite electrode has minimal charge transfer resistance and greater electron transfer ability. Therefore, the current study presents a facile formation of Z-scheme catalyst and offers a sustainable method to eradicate water impurities and hydrogen generation by renewable solar energy.

Cobalt-promoted palladium confined in HZSM-5 zeolite for toluene storage and oxidation capacity in humid environment

Although oxide-zeolite bifunctional catalysts with storage and oxidation capacity was efficient for VOCs removal, the inevitable moisture in the air usually harms the catalysts performance. Herein, cobalt was in situ confined with palladium in HZSM-5 by a one-pot hydrothermal method and significantly improved the storage and oxidation abilities in humid air. The optimal Pd0.90Co0.10@Z5 catalyst showed a considerable toluene storage capacity of 76.8 mg/g (100 ppm toluene/humid air, GHSV=60,000 h−1), and the best oxidation activity (600 ppm toluene/humid air, GHSV=60,000 h−1, TOFPd = 15.5 × 10−3 s−1 at 200 °C). Pd0.90Co0.10@Z5 formed an intrapenetrated mesoporous structure with the smallest Pd clusters of dAV=2.6 nm. The synergistic effect between palladium and cobalt promoted electron transfer and Pd0.90Co0.10@Z5 had the highest Pd2+/Pd0 ratio of 3.50. Co2+ can activate water to form Co(OH)3 and provide an additional ·OH oxidation pathway, ·OH and reactive oxygen species (O*) together promote the deep oxidation of intermediates. This work provides a novel approach that bimetallic collaboration combined with porous zeolite can improve the catalytic performance and water resistance.

Analyzing the active sites of carbocatalyst for peroxydisulfate activation: Specific surface area or electrochemical surface area?

Persulfates activation by various nanomaterials has been intensively reported for advanced oxidation processes (AOPs), and substantial progress has been made in understanding the mechanism. However, most of the published articles only present the unnormalized catalytic properties, which generated confusion to compare different catalysts and identify the active sites. Herein, we presented electrochemical surface area (ECSA) as a practical normalized method and confirmed the primary active sites in N-doped graphene. By controlling the aggregation state of graphene sheets to adjust the activity of doped graphite-N species, the active sites for peroxydisulfate (PDS) activation were accurately estimated. In further experiments, specific surface area (SSA, by N2-physisorption and methylene blue adsorption) and ECSA were adopted to conclude the normalized oxidation rate constant and graphitic-N was confirmed as the primary site in nitrogen-doped graphene for the carbocatalyst/PDS system. The normalized results revealed that SSA derived from inert gas on materials could not reflect the true active sites at solid-liquid interface, while ECSA considering the operated solid-liquid situation can be used for accurate estimation of the active sites. Therefore, this study suggests that ECSA integrates the properties of both kinetics and thermodynamics, which can be adopted as a useful methodology for analyzing nano-sized environmental catalysts performance.