Platinum on nitrogen doped graphene and tungsten carbide supports for ammonia electro-oxidation reaction

Ammonia electrooxidation reaction involving multistep electron-proton transfer is a significant reaction for fuel cells,hydrogen production and understanding nitrogen cycle.Platinum has been established as the best electrocatalyst for ammonia oxidation in aqueous alkaline media.In this study,Pt/nitrogen-doped graphene(NDG)and Pt/tungsten monocarbide(WC)/NDG are synthesized by a wet chemistry method and their ammonia oxidation activities are compared to commercial Pt/C.Pt/NDG exhibits a specific activity of 0.472 mA·cm^(-2),which is 44%higher than commercial Pt/C,thus establishing NDG as a more effective support than carbon black.Moreover,it is demonstrated that WC as a support also impacts the activity with further 30%increase in comparison to NDG.Surface modification with Ir resulted in the best electro-catalytic activity with Pt-IrAVC/NDG having almost thrice the current density of commercial Pt/C.This work adds insights regarding the role of NDG and WC as efficient supports along with significant impact of Ir surface modification.

Alloying cobalt with ruthenium in nitrogen doped graphene layers for developing highly active hydrogen evolution electrocatalysts in alkaline media

Subject Code:B01With the support by the National Natural Science Foundation of China,a creative study by the research group led by Prof.Chen Qianwang(陈乾旺)from the University of Science and Technology of China and High Magnetic Field Laboratory,Hefei Institutes of Physical Science,Chinese Academy of

Atomic Layer Coated Al_(2)O_(3) on Nitrogen Doped Vertical Graphene Nanosheets for High Performance Sodium Ion Batteries

Heteroatom doped graphene materials are considered as promising anode for high-performance sodium-ion batteries(SIBs).Defective and porous structure especially with large specific surface area is generally considered as a feasible strategy to boost reaction kinetics;however,the unwanted side reaction at the anode hinders the practical application of SIBs.In this work,a precisely controlled Al_(2)O_(3)coated nitrogen doped vertical graphene nanosheets(NVG)anode material has been proposed,which exhibits excellent sodium storage capacity and cycling stability.The ultrathin Al_(2)O_(3)coating on the NVG is considered to help construct an advantageous interface between electrode and electrolyte,both alleviating the electrolyte decomposition and enhancing sodium adsorption ability.As a result,the optimal Al_(2)O_(3)coated NVG materials delivers a high reversible capacity(835.0 mAh g^(-1))and superior cycling stability(retention of 92.3%after 5000 cycles).This work demonstrates a new way to design graphene-based anode materials for highperformance sodium-ion batteries.

Doped graphene/carbon black hybrid catalyst giving enhanced oxygen reduction reaction activity with high resistance to corrosion in proton exchange membrane fuel cells

Nitrogen doping of the carbon is an important method to improve the performance and durability of catalysts for proton exchange membrane fuel cells by platinum–nitrogen and carbon–nitrogen bonds. This study shows that p-phenyl groups and graphitic N acting bridges linking platinum and the graphene/carbon black(the ratio graphene/carbon black = 2/3) hybrid support materials achieved the average size of platinum nanoparticles with(4.88 ± 1.79) nm. It improved the performance of the lower-temperature hydrogen fuel cell up to 0.934 W cm^(-2) at 0.60 V, which is 1.55 times greater than that of commercial Pt/C. Doping also enhanced the interaction between Pt and the support materials, and the resistance to corrosion, thus improving the durability of the low-temperature hydrogen fuel cell with a much lower decay of 10 mV at 0.80 A cm^(-2) after 30 k cycles of an in-situ accelerated stress test of catalyst degradation than that of 92 mV in Pt/C, which achieves the target of Department of Energy(<30 mV). Meanwhile,Pt/Nr EGO_(2)-CB_(3) remains 78% of initial power density at 1.5 A cm^(-2) after 5 k cycles of in-situ accelerated stress test of carbon corrosion, which is more stable than the power density of commercial Pt/C, keeping only 54% after accelerated stress test.

Electronic Transport Properties of Diblock Co-Oligomer Molecule Devices Sandwiched between Nitrogen Doping Armchair Graphene Nanoribbon Electrodes

We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-principles method based on density functional theory. Among the three models M1–M3, M1 is not doped with a heteroatom. In the left parts of M2 and M3, nitrogen atoms are doped at two edges of the nanoribbon. In the right parts, nitrogen atoms are doped at one center and at the edges of M2 and M3, respectively. Comparisons of M1, M2 and M3 show obvious rectifying characteristics, and the maximum rectification ratios are up to 42.9 in M2. The results show that the rectifying behavior is strongly dependent on the doping position of electrodes. A higher rectification ratio can be found in the dipyrimidinyl-diphenyl molecular device with asymmetric doping of left and right electrodes, which suggests that this system has a broader application in future logic and memory devices.

Nitrogen-doped pyrogenic carbonaceous matter facilitates azo dye decolorization by sulfide: The important role of graphitic nitrogen

Pyrogenic carbonaceous matter(PCM) catalyzes azo dye decolorization by sulfide, but the nitrogen doping catalytic mechanisms are poorly understood. In this study, we found that stagnate time of azo dye methyl orange(MO) decolorization was reduced to 0.54-18.28 min in the presence of various nitrogen-doped graphenes(NGs), remarkably lower compared to graphene itself. Particularly, graphitic nitrogen played a critical role in NGs-catalyzed MO decolorization by sulfide. Gas chromatography-mass spectrometry and in-situ surface Raman analysis demonstrated that doping nitrogen, especially graphite one facilitated reactive intermediate polysulfides formation. This is attributed to the improved electron conductivity through graphitic nitrogen doping, and the enhanced interactions between sulfide and carbon atoms bonded to graphitic nitrogen. This study not only provides a better understanding of PCM impact on transformations and fates of organic pollutants in natural environments, but also offer a new regulation strategy for more efficient wastewater treatment processes in PCM-catalyzed engineering systems.

A nanoporous nitrogen-doped graphene for high performance lithium sulfur batteries

A nanoporous N-doped reduced graphene oxide（p-N-rGO） was prepared through carbothermal reaction between graphene oxide and ammonium-containing oxometalates as sulfur host for Li-S batteries.The p-N-rGO sheets have abundant nanopores with diameters of 10-40 nm and the nitrogen content is 2.65 at%.When used as sulfur cathode,the obtained p-N-rGO/S composite has a high reversible capacity of 1110mAhg^-1 at 1C rate and stable cycling performance with 781.8 mAhg-1 retained after 110 cycles,much better than those of the rGO/S composite.The enhanced electrochemical performance is ascribed to the rational combination of nanopores and N-doping,which provide efficient contact and wetting with the electrolyte,accommodate volume expansion and immobilize polysulfides during cycling.

Competitive role of nitrogen functionalities of N doped GO and sensitizing effect of Bi_(2)O_(3)QDs on TiO_(2)for water remediation

The promising solar irradiated photocatalyst by pairing of bismuth oxide quantum dots(BQDs)doped TiO_(2)with nitrogen doped graphene oxide(NGO)nanocomposite(NGO/BQDs-TiO_(2))was fabricated.It was used for degradation of organic pollutants like 2,4-dichlorophenol(2,4-DCP)and stable dyes,i.e.Rhodamine B and Congo Red.X-ray diffraction(XRD)profile of NGO showed reduction in oxygenic functional groups and restoring of graphitic crystal structure.The characteristic diffraction peaks of TiO_(2)and its composites showed crystalline anatase TiO_(2).Morphological images represent spherical shaped TiO_(2)evenly covered with BQDs spread on NGO sheet.The surface linkages of NO-O-Ti,C-O-Ti,Bi-O-Ti and vibrational modes are observed by Fourier transform infrared spectroscopy(FTIR)and Raman studies.BQDs and NGO modified TiO_(2)results into red shifting in visible region as studied in diffused reflectance spectroscopy(DRS).NGO and BQDs in TiO_(2)are linked with defect centers which reduced the recombination of free charge carriers by quenching of photoluminescence(PL)intensities.X-ray photoelectron spectroscopy(XPS)shows that no peak related to C-O in NGO/BQDs-TiO_(2)is observed.This indicated that doping of nitrogen into GO has reduced some oxygen functional groups.Nitrogen functionalities in NGO and photosensitizing effect of BQDs in ternary composite have improved photocatalytic activity against organic pollutants.Intermediate byproducts during photo degradation process of 2,4-DCP were studied through high performance liquid chromatography(HPLC).Study of radical scavengers indicated that O_(2)^(·-) has significant role for degradation of 2,4-DCP.Our investigations propose that fabricated nanohybrid architecture has potential for degradation of environmental pollutions.

One-step preparation of Fe_xO_y/N-GN/CNTs heterojunctions as a peroxymonosulfate activator for relatively highly-efficient methylene blue degradation

Persulfate decontamination technologies utilizing radical‐driven processes are powerful tools for the treatment of a broad range of impurities.However,the design of high‐performance catalytic activators with multi‐functionality remains a great challenge.Therefore,in this study,three‐dimensional multifunctional FexOy/N‐GN/CNTs(N‐GN:nitrogen‐doped graphene,CNTs:carbon nanotubes)heterojunctions,which can be employed as microwave absorbers and catalysts,were synthesized via a solvothermal method and applied to activate peroxymonosulfate for the degradation of methylene blue(MB).X‐ray diffraction(XRD),Fourier transform infrared spectrometer(FTIR),scanning electron microscope(SEM),and X‐ray photoelectron microscopy(XPS)analyses revealed that the FexOy were anchored in‐situ onto the N‐GN network.Using MB as the model organic dye,various factors,such as degradation systems,PMS loading,initial organic pollutant concentration,and catalyst dosage were optimized.The results revealed that the remarkable efficiency was attributable to the synergistic effects of carbon,nitrogen,and iron‐based species.The oxidation system corresponded to the pseudo‐first‐order kinetic with a k value of^0.33 min^-1.It was demonstrated that both SO4^-and OH^-were the predominant reactive species through quenching experiments.Because these heterojunctions were employed as microwave absorbers and have a semiconductor‐like texture,the Fe/N co‐rich hierarchical porous carbon skeleton favored electron transport and storage.These heterojunctions increase the options for transitional metal catalysts and highlights the importance of designing other heterojunctions for specific applications,such as supercapacitors,energy storage,CO2 capture,and oxygen reduction electrocatalysts.