rGO Catalyst Research Articles

Bi‐Functional Co/Al Modified 1T‐MoS2/rGO Catalyst for Enhanced Uranium Extraction and Hydrogen Evolution Reaction in Seawater

Uranium is a key element in the preparation of nuclear fuel. An electrochemical uranium extraction technique is proposed to achieve high efficiency uranium extraction performance through HER catalyst. However, it is still a challenge to design and develop a high-performance hydrogen evolution reaction (HER) catalyst for rapid extraction and recovery of uranium from seawater. Herein, a bi-functional Co, Al modified 1T-MoS2 /reduced graphene oxide (CA-1T-MoS2 /rGO) catalyst, showing a good HER performance with a HER overpotential of 466mV at 10mA cm-2 in simulated seawater, is first developed. Benefiting from the high HER performance of CA-1T-MoS2 /rGO, efficient uranium extraction is achieved with a uranium extraction capacity of 1990mg g-1 in simulated seawater without post-treatment, exhibiting a good reusability. The results of experiments and density functional theory (DFT) show that a high uranium extraction and recovery capability is attributed to the synergy effect of the improved HER performance and the strong adsorption capacity between U and OH*. This work provides a new strategy for the design and preparation of bi-functional catalysts with high HER performance and uranium extraction and recovery capabilities in seawater.

Synthesis of rGO supported Cu@FeCo catalyst and catalytic hydrolysis of ammonia borane.

Highly dispersed Cu@FeCo/rGO catalysts have been prepared by two-step reduction method and used for hydrogen production from ammonia borane (NH3BH3, AB) hydrolysis at 298 K. The activity and reusability of synthesized composite catalyst were much more higher than Cu@FeCo for AB hydrolysis dehydrogenation at 298 K. Kinetic study manifested that AB hydrolysis dehydrogenation with Cu@FeCo/rGO catalysts was approaching to the first order at different catalyst concentrations. The hydrolysis reaction completed within four minutes, and its maximum hydrogen production rate reached to 7863.0 ml min-1 g-1 at 298 K.

Investigations of the ODS process utilizing CNT- and CNF-based WO3 catalystsfor environmental depollution: experimental and theoretical aspects.

In this contribution, CoW/X materials (X = CNT or CNF) were utilized as oxidative desulfurization (ODS) catalysts for the removal of dibenzothiophene (DBT) from a model fuel (n-decane), incorporating the H2O2 as an efficient oxidant. Different operating conditions were investigated. Both compounds revealed high desulfurization efficiency using milder operating conditions leading to low levels of the DBT compound since only 1h while using a low ratio of H2O2/S = 6. Among synthesized compounds, the CoW (15)/CNT showed superior DBT conversion through the ODS process. In other words, the highest sulfur removal efficiency of 100% for a feed sulfur content of 500ppm was determined in a 40-min duration under optimum conditions. This was satisfyingly more effective than a recently reported CoW (20)/rGO catalyst. The characterization of synthesized catalysts was performed in order to evaluate their physicochemical properties. Moreover, product identification of the oxidation desulfurization process was performed using the GC-Mass, FTIR, and NMR techniques where it was found that this process was that of a single product. These experimental studies were complemented with density functional theory (DFT) investigations, which indeed shed important light on understanding the adsorption mechanisms as well as electronic properties of the system undertaken.

Cobalt-Graphene Catalyst for Selective Hydrodeoxygenation of Guaiacol to Cyclohexanol.

Herein, cobalt-reduced graphene oxide (rGO) catalyst was synthesized with a practical impregnation–calcination approach for the selective hydrodeoxygenation (HDO) of guaiacol to cyclohexanol. The synthesized Co/rGO was characterized by transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), and H2 temperature-programmed reduction (H2-TPR) analysis. According to the comprehensive characterization results, the catalyst contains single Co atoms in the graphene matrix and Co oxide nanoparticles (CoOx) on the graphene surface. The isolated Co atoms embedded in the rGO matrix form stable metal carbides (CoCx), which constitute catalytically active sites for hydrogenation. The rGO material with proper amounts of N heteroatoms and lattice defects becomes a suitable graphene material for fabricating the catalyst. The Co/rGO catalyst without prereduction treatment leads to the complete conversion of guaiacol with 93.2% selectivity to cyclohexanol under mild conditions. The remarkable HDO capability of the Co/rGO catalyst is attributed to the unique metal–acid synergy between the CoCx sites and the acid sites of the CoOx nanoparticles. The CoCx sites provide H while the acid sites of CoOx nanoparticles bind the C-O group of reactants to the surface, allowing easier C-O scission. The reaction pathways were characterized based on the observed reaction–product distributions. The effects of the process parameters on catalyst preparation and the HDO reaction, as well as the reusability of the catalyst, were systematically investigated.

Heteroatom doping effect of Pt/rGO catalysts for formaldehyde abatement at ambient temperature

The effect of doping with different heteroatoms (N, P, S, and F atoms) on physicochemical properties of reduced graphene oxide (rGO) catalysts and their performances on formaldehyde (HCHO) oxidation is investigated in this study. Nitrogen-doped rGO with a loading of 1 wt% Pt (Pt/N-rGO) sample exhibits a superior HCHO conversion of 82% at a gas hourly space velocity (GHSV) of 50,000 mL/(g × h) at ambient temperature. In addition, the Pt/N-rGO catalyst remained an outstanding activity and stability at room temperature after testing continuously for 48 h. A series of characterization results showed that nitrogen-doping significantly increased the defect degree and specific surface area of rGO compared with rGOs doped with other heteroatoms, promoted the dispersion of Pt nanoparticles (NPs), and produced more zero-valent Pt (Pt0). In addition, the average particle size of the Pt NPs in the samples doping with heteroatoms decreased from 36.4 nm to 4.4 nm. Combined with the results of HCHO-DRIFTS, the highly dispersed Pt NPs on the surface of Pt/N-rGO sample was conducive to activate oxygens and further transfer the formate intermediate.

Enhanced electrocatalytic activities of MoO3/rGO nanocomposites for oxygen reduction reaction

AbstractBACKGROUNDThe availability of highly active, low‐cost and stable oxygen reduction reaction (ORR) electrocatalysts remains a barrier to the development of energy techniques. This study presents molybdenum trioxide/reduced graphene oxide (MoO3/rGO) composite as an effective electrocatalytic material for ORR.RESULTSThe nanosized MoO3 particles loaded on rGO as an efficient ORR catalyst was prepared via a two‐step method. The MoO3(0.1)/rGO nanocomposite showed the highest content of Mo6+ and rGO carbon among rGO and MoO3/rGO. The MoO3(0.1)/rGO showed the highest limiting current density of −3.04 mA cm−2 at 0.2 V versus reversible hydrogen electrode, which was comparable to the commercial 10% Pt/C in the present work. The electron transfer number of 2.74 on MoO3(0.1)/rGO indicated ORR selectivity towards the four‐electron pathway was not very high. The electrochemical active surface area of the MoO3(0.1)/rGO nanocomposite was 9.94 cm2, which was about twice the commercial 10% Pt/C. The small Tafel slope of 57.56 mV dec−1 confirms the high ORR activity of the MoO3(0.1)/rGO catalyst. The MoO3(0.1)/rGO also showed good stability under alkaline conditions and better methanol tolerance compared to the commercial 10% Pt/C.CONCLUSIONThe increased activity of the MoO3(0.1)/rGO composite may be attributed to the higher content of Mo6+ and rGO carbon in the catalyst. Performance of the catalysts may be further improved by optimizing the experimental conditions. The synthesized MoO3/rGO composite is a potential alternative electrocatalyst for ORR. © 2022 Society of Chemical Industry (SCI).

Persulfate activation by magnetic SnS2-Fe3O4/rGO nanocomposite under visible light for detoxification of organophosphorus pesticide

In this study, a novel SnS2-Fe3O4/rGO catalyst was applied to activate persulfate (PS) in the removal of diazinon under visible-light irradiation. Characteristics of the SnS2-Fe3O4/rGO nanocomposite were analyzed via different techniques. The results indicate that 5 mg L−1 diazinon solution could be almost completely degraded in 40 min with 0.5 g L−1 catalyst and 1 mM L−1 PS, and TOC can be reduced 78%. Based on the scavenging experiments a possible reaction mechanism was proposed. The results revealed that the removal of diazinon followed pseudo-first-order kinetics. Then, the intermediates produced in the system were determined using LC-MS/MS. The toxicity test indicated that the SnS2-Fe3O4/rGO-PS system was effective at decreasing the toxicity of diazinon. It was found that the SnS2-Fe3O4/rGO-PS system had good catalytic performance and reusability. The results of this study provided beneficial information for the application of the SnS2-Fe3O4/rGO-PS system in organic contaminants degradation.

Achieve high-efficiency hydrogen storage of MgH2 catalyzed by nanosheets CoMoO4 and rGO

The development of high-efficiency carbon-based multifunctional catalysts is of great significance for improving solid-state hydrogen storage materials . Herein, it was confirmed that CoMoO 4 sheet-like nanocatalysts uniformly supported on the surface of reduced graphene oxide (CoMoO 4 /rGO) were successfully prepared by a simple hydrothermal reaction . The novel CoMoO 4 /rGO catalyst was subsequently doped into MgH 2 to improve its hydrogen storage performance. MgH 2 –10 wt% CoMoO 4 /rGO starts to release hydrogen at around 204 °C, which is about 36 °C and 156 °C lower than that of MgH 2 −10 wt%CoMoO 4 and pure MgH 2 , respectively. In addition, 6.25 wt% H 2 can be released within 10 min at 300 °C. After complete dehydrogenation , H 2 can be absorbed below 80 °C. Meanwhile, it can absorb 4.2 wt% H 2 in 20 min under the condition of 150 °C and 3 MPa. Moreover, the activation energy of hydrogen absorption and dehydrogenation of MgH 2 –10 wt%CoMoO 4 /rGO composites are reduced by 31.44 kJ mol −1 and 33.78 kJ mol −1 , respectively, compared with pure MgH 2 . Cycling experiment shows that the MgH 2 –10 wt%CoMoO 4 /rGO composite system can still maintain about 98% of the hydrogen storage capacity after 10 cycles. Furthermore, studies on the catalytic mechanism show that the synergistic effect between the in-situ generated MgO, Co 7 Mo 6 and Mo may help to promote the diffusion of H 2 , thereby improving the MgH 2 Hydrogen storage properties. • MgH 2 –10 wt%CoMoO 4 /rGO composite system was reported for the first time. • MgH 2 –10 wt%CoMoO 4 /rGO composite material starts dehydrogenation at about 204 °C. • MgH 2 –CoMoO 4 /rGO composites showed promising kinetic properties. • MgH 2 –CoMoO 4 /rGO composites showed good cyclic stability. • MgO, Mo and Co 7 Mo 6 were formed in situ during the reaction.

N-Doped and Sulfonated Reduced Graphene Oxide Supported PtNi Nanoparticles as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction

N-doping and sulfonation is prepared on the reduced graphene oxide (rGO) support for PtNi nanoparticles (PtNi/S-(N)rGO) by a simple method of hydrothermal synthesis and thermal decomposition. The specific surface area increases from 180.7 m2/g of PtNi/rGo to 293.5 m2/g of PtNi/S-(N)rGO. The surface morphology shows wrinkles sites, which are separated by the sulfonated groups. The catalytic stability and efficiency are improved by the anchoring effect of sulfonated groups and evenly distribution of nanoparticles, respectively. The synergistic effect of N-doping and sulfonation can be in favor of catalytic efficiency by the increase of number of electron transfer. The half-wave potential of the PtNi/S-(N)rGO catalyst is up to 0.632 V, a small positive shift compared to the Pt/C catalyst. The durability of the PtNi/S-(N)rGO is 2.6 times higher than of the Pt/C catalyst after 5000 repeated cycles. The peak power of the PtNi/S-(N)rGO catalyst increased 37.5% compared to the Pt/C catalyst. Therefore, the stability and catalytic efficiency are improved by the PtNi/S-(N)rGO catalyst applied in proton exchange membrane fuel cell (PEMFC) compared to the commercial Pt/C catalyst.

Edge-halogenated graphene nanosheets as an efficient metal-free electrocatalyst for hydrogen evolution reaction

Application of carbonic materials as catalysts has recently been considered due to some advantages like tunable molecular structures, easy synthesis methods, abundance, and high tolerance in acidic and alkaline media. Here, a new metal-free electrocatalyst of halogenated reduced graphene oxide was prepared using cyclic voltammetry X (F, Br, and I)-RGO electrodeposition method. The prepared electrocatalysts were studied as a novel metal-free electrocatalyst for the hydrogen evolution reaction, and the presence of several halogen and oxygen functional groups on the surface of nanosheets was verified by the furrier transform infra-red, FT-IR, spectroscopy, and the presence of doped halogens on the RGO surface was confirmed by energy-dispersive X-ray, EDX, spectroscopy. The structural features and surface morphology of electrocatalysts were investigated by scanning electron microscopy (SEM) analysis. The electrochemical treatment of the X (F, Br, I)-RGO electrode was studied by some techniques like electrochemical impedance spectroscopy, EIS, chronoamperometry, CA, and linear sweep voltammetry, LSV. The X (F, Br, I)-RGO catalyst showed a lower onset potential (−0.81 V. vs. SHE), higher exchange current density (3.1 × ×10−1 mA cm−2), and lower charge transfer resistance (1.09 Ω cm2) related to the RGO catalyst due to the high active sites by heteroatoms and graphene nanosheets.

Deep oxidative desulfurization via rGO-immobilized tin oxide nanocatalyst: Experimental and theoretical perspectives

In this contribution, reduced grapheme oxides (rGO) with immobilized tin oxide (SnO2) nanocatalysts were synthesized via the Incipient Wetness Impregnation (IWI) method. To characterize the SnO2/rGO composites, several analyses including the; XRD, Raman, FTIR, ICP-OES, BET-BJH, XPS, TEM, and TPD were utilized. Then the effects of parameters including reaction time, total metal loading, and the initial sulfur concentration of model fuel in the dibenzothiophene (DBT) oxidation desulfurization process were evaluated. After determining the optimal conditions for the aforementioned parameters, the influences of 3 effective factors of the molar ratio of oxidant/substrate (O/S), the molar ratio of catalyst/substrate (Cat/S), and reaction temperature were investigated by applying response surface methodology (RSM). Results revealed that through employing the SnO2 (15)/rGO catalyst, the DBT conversion of 96% was obtained at the following optimum conditions: time = 180 min, initial sulfur concentration = 500 ppm, molar ratio of O/S = 30, temperature = 60 °C and molar ratio of Cat/S = 0.06. Next, 1H NMR and FTIR techniques were performed for the final product assessment. Ultimately, to investigate the importance of the rGO upon the DBT oxidation, density functional theory (DFT) calculations were utilized. Interaction energy, Reactivity parameters, ESP, and RDG results revealed the influence of the rGO in the adsorption of the DBT through the π–π interactions.

Synthesis and Characterization of rGO@ZnO Nanocomposites for Esterification of Acetic Acid.

In the present work, the aim is to synthesize reduced graphene oxide (rGO) and zinc:reduced graphene oxide composite catalysts (ZnO:rGO) for esterification of acetic acid with n-heptanol. The physical and chemical characteristics of the rGO and rGO-metal oxide composite catalysts such as textural surface characteristics, surface morphology, thermal stability, functional groups, and elemental analysis were studied. The surface areas of rGO, ZnO(0.5 M), and ZnO(1 M) were recorded, respectively, at 31.72, 27.65, and 36.19 m2 g–1. Furthermore, esterification reaction parameters such as the reaction time, catalyst dosage, and reaction temperature for acetic acid were optimized to check the feasibility of rGO-metal oxide composites for a better conversion percentage of acetic acid. The optimized catalyst was selected for further optimization, and the optimum reaction parameters found were 0.1 wt % of catalyst, 160 min reaction duration, and 100 °C reaction temperature with a maximal yield of 100%. At 110 °C, the reaction conducted in the presence of 0.1 g of catalyst displayed more yield than the uncatalyzed reaction.

Liquid “Syngas” Based on Supercritical Water and Graphite Oxide/TiO2 Composite as Catalyst for CO2 to Organic Conversion

The conversion of carbon monoxide into organic substances is one of the top topics of modern science due to the development of industry and the climate changes caused by it on the one hand, and the possibility of obtaining an economic effect on the other, as it could allow for partial recovery of fuels. A problem in this regard has always been the low solubility of CO2 in water, which eliminated the possibility of easy converting carbon dioxide into the liquid. The development of research on water critical states revealed the fact that water in a subcritical state has a much higher ability to dissolve gases. And this effect was used to obtain the "liquid synthesis gas" model presented in this paper. Equally important was the selection of an appropriate catalyst that would increase the efficiency of the conversion process by generating hydrogen in the system under the influence of cold plasma. In this work we present the studies of transformation of CO2 dissolved in supercritical water using partially reduced graphite oxide—nanometric titania composite (RGO-TiO2) as catalyst, due to the ability of RGO to generate hydrogen in the water environment (water splitting) under the influence of various physical factors, especially cold plasma. The RGO catalyst was stabilized with titanium oxide to obtain higher activity at lower RGO concentrations in the system. Therefore, research on conversions was preceded by a thorough analysis of CO2 solubility in supercritical water, as well as an analysis of the structural, morphological, and spectroscopic properties of the catalyst.Graphic General scheme of cold plasma reactor.

Engineering core–shell Co9S8/Co nanoparticles on reduced graphene oxide: Efficient bifunctional Mott–Schottky electrocatalysts in neutral rechargeable Zn–Air batteries

It is significant for the rational construction of the high–efficient bifunctional electrocatalysts for in–depth understandings of how to improve the electron transfer and ion/oxygen transport in catalyzing oxygen reduction reaction and oxygen evolution reaction (ORR and OER), but still full of vital challenges. Herein, we synthesize the novel “three–in–one” catalyst that engineers core–shell Mott–Schottky Co9S8/Co heterostructure on the defective reduced graphene oxide (Co9S8/Co–rGO). The Co9S8/Co–rGO catalyst exhibits abundant Mott–Schottky heterogeneous–interfaces, the well–defined core–shell nanostructure as well as the defective carbon architecture, which provide the multiple guarantees for enhancing the electron transfer and ion/oxygen transport, thus boosting the catalytic ORR and OER activities in neutral electrolyte. As expected, the integrated core–shell Mott–Schottky Co9S8/Co–rGO catalyst delivers the most robust and efficient rechargeable ZABs performance in neutral solution electrolytes accompanied with a power density of 59.5 mW cm−2 and superior cycling stability at 5 mA cm−2 over 200 h. This work not only emphasizes the rational designing of the high–efficient bifunctional oxygen catalysts from the fundamental understanding of accelerating the electron transfer and ion/oxygen transport, but also sheds light on the practical application prospects in more friendly environmentally neutral rechargeable ZABs.

Non-covalent functionalization of triazine framework decorated over reduced graphene oxide as a novel anode catalyst support for glycerol oxidation

The electrocatalytic performance of platinum-gold(Pt-Au) nanoparticles decorated non-covalent functionalization of triazine framework derived from poly(cyanuric chloride-co-biphenyl) over reduced graphene oxide (Poly(CC-co-BP)-RGO) was carried out for glycerol in basic medium and their oxidized products were analysed to support the enhanced activity. The surface morphology and the composition of the catalyst were obtained using X-ray diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The electrooxidation results illustrate that the Pt-Au/Poly(CC-co-BP)-RGO catalyst exhibits improved catalytic activity and stability when compared to that of Pt/Poly(CC-co-BP)-RGO, Pt/Poly(CC-co-BP) and Pt/RGO catalysts. The better performed Pt-Au/Poly(CC-co-BP)-RGO catalyst was used as electrode material for the fabrication of single test direct alkaline glycerol fuel cell. The fuel cell performance was tested by varying the concentration of glycerol and the temperature of the cell. The maximum power density of 122.96 mWcm−2 was obtained for Pt-Au/Poly(CC-co-BP)-RGO catalyst in single direct alkaline glycerol fuel cell under the optimum concentration of 2.0 M glycerol at 70 °C.

One-pot co-reduction synthesis of orange-like Pd@Co@P nanoparticles supported on rGO for catalytic hydrolysis of ammonia borane

Transition metal phosphide based orange-like Pd@Co@P nanoparticles supported on reduced graphene oxide (Pd@Co@P/rGO) have been synthesized by a one-pot co-reduction at room temperature using methylamine borane (MeAB) as the reducing agent. The prepared Pd@Co@P/rGO nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), selected area electron diffraction (SAED) and confocal Raman microscopy (Raman). Compared with Pd/rGO and Pd@Co/rGO, the Pd@Co@P/rGO catalyst has higher catalytic activity for the hydrolytic production of ammonia borane (AB) with the turnover frequency value (TOF) of 127.57 min−1 and the activation energy of 39.05 kJ mol−1. This excellent catalytic performance may be caused by the orange-like structure and good dispersion of Pd@Co@P/rGO nanoparticles, and the synergistic electron interactions between palladium, cobalt, and phosphorus.

A Ni nanoparticles encapsulated in N-doped carbon catalyst for efficient electroreduction CO2: Identification of active sites for adsorption and activation of CO2 molecules

Electrochemical CO2 reduction (ECR) offers a promising strategy to achieve global carbon balance and mitigate the global climate. However, it is still a challenge to fabricate excellent catalyst and illustrate the active site for adsorption and activation of CO2 molecules. Herein, we develop a reduced graphene oxide-supported N-doped carbon-encapsulated nickel (Ni@N-C/rGO) catalyst for ECR to CO. The optimal Ni@N-C/rGO(4,4′-bipy) catalyst exhibits high catalytic activity, selectivity and stability with a current density of 20 mA cm−2 and Faradaic efficiency of 88% toward CO at −0.97 V vs. RHE for 10 h. The well-designed poisoning and control experiments deduce that the catalytic activity originates from the N-doped carbon layer coated on Ni particles. Density functional theory calculations suggest that pyrrolic-N is the optimal active site for the adsorption and activation of CO2 molecules, and the spontaneous charge transfer from Ni 3d electrons to the π orbitals of the N-C skeleton promotes the easy desorption of *CO from the active sites, thereby improving the ECR activity.

Synthesis of low‐cost Co‐Sn‐Pd/rGO catalysts via ultrasonic irradiation and their electrocatalytic activities toward oxygen reduction reaction

AbstractReduced graphene supported Co‐Sn‐Pd nanoparticle catalysts(Co0.2SnxPdy/rGO, x + y = 0.4) were successfully synthesized by reducing the trace amounts of ions (Pd2+, Sn2+, and Co2+) in the presence of reduced graphene via an ultrasonic irradiation method. Characterization of the Co0.2SnxPdy/rGO catalysts by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) indicates that the Co0.2Sn0.2Pd0.2/rGO catalyst with a mean diameter of ~3.8 nm is close to a single‐phase solid solution. X‐ray photoelectron spectroscopy (XPS) shows the binding energy of metallic Pd shifts to a higher angle in the Co0.2SnxPdy/rGO (x + y = 0.4) catalysts, indicating a shift of Pd electronic centre upon alloying with Co and Sn. Conventionally, ternary Co‐Sn‐Pd/rGO catalysts show greater oxygen reduction reaction (ORR) activities and durability than binary Pd‐Co/rGO catalyst and 20 wt% Pt/C catalyst even at a very low Pd content. Among of the synthetic catalysts, the Co0.2Sn0.2Pd0.2/rGO catalyst exhibits the best ORR activity (E1/2 = 0.91 V, k = −57 mV · dec−1) and dominates a 4‐electron pathway in the ORR process (n = 3.95 ± 0.09, H2O2<4%). Also, the Co0.2SnxPdy/rGO (x + y = 0.4) catalysts display a remarkable advantage of high methanol tolerance compared to that of the commercial 20 wt% Pt/C catalyst, which make them potential candidates for direct methanol fuel cells.

Oxidative desulfurization of a model liquid fuel over an rGO-supported transition metal modified WO3 catalyst: Experimental and theoretical studies

The XW/rGO compounds (XW = Co or Ni modified WO3) have has been utilized as catalysts in the oxidative desulfurization (ODS) process of a liquid model fuel containing dibenzothiophene (DBT). Various characterization methods were carried out to complete evaluations of the prepared catalysts. Moreover, using the GC–MS method, it became clear that the final product of the process was dibenzothiophene sulfone (DBTO2). Furthermore, results showed that under the optimized conditions (oxidant to substrate molar ratio = 6, 75 °C and catalyst to substrate molar ratio = 0.08), the DBT content of a model fuel was declined by 100% only within a reaction duration time of 45 min using the CoW (20)/rGO catalyst. Also, the results obtained from the DFT study revealed that, for an efficient reaction over the surface of the catalyst, along with the S⋯O chalcogen interaction, the strength of the H-bonds interactions (H⋯O) between the DBT and active sites on catalysts may have tuned-up the driving force of the reaction. Ultimately, the results indicated that the charge transfer at the XW/rGO interface may be tuned by selecting impurity used alongside the WO3 species.

Pd–SnO2 heterojunction catalysts anchored on graphene sheets for enhanced oxygen reduction

Palladium (Pd) has received extensive attention as the substitute for platinum to work as efficient catalyst towards the oxygen reduction reaction (ORR) owing to its high intrinsic activity. However, the Pd catalyst usually performs inferior catalytic stability in the practical electrochemical test. Here, we report a novel design of constructing efficient ORR catalyst with Pd/SnO2 heterojunctions uniformly loaded on the reduced graphene oxide sheets (Pd@SnO2/rGO). The highly conductive rGO sheets are beneficial to increase the electron transfers during the ORR process and the SnO2 support can induce tensile-strain and electron-rich features for Pd nanocrystals in the Pd/SnO2 heterojunctions. The electrochemical results illustrate that the Pd@SnO2/rGO catalyst has higher ORR activity compared to commercial Pd/C and shows remarkable catalytic stability with 1 mV of negative shift in half-wave potential over 20000 cycles of accelerated durability tests. Moreover, the Zn-air battery assembled with Pd@SnO2/rGO cathode exhibits a 2.8-fold higher specific capacity than that with Pd/C cathode.