Fabrication Of Carbon Based Nanomaterials And Their Applications In Catalyzing Water Splitting And Electrochemical Sensor

Material is the basis of human society.The development of material promotes the social progress.In recent years,the design and fabrication of high performance novel materials is urgently needed since the energy crisis and environmental problems are becoming increasingly serious.Nanomaterial has attracted much attention for its specific physical and chemical properties that benefits from the nanoscale.Among them,carbon based nanomaterials have played important roles in the construction of low cost and high performance energy storage and transfer devices,and biosensors.The present work introduced the properties,fabrications and applications of several carbon based nanomaterials and overviewed the development of such materials applied as electrocatalyst for water splitting and constructing electrochemical sensors.And on this basis,we developed several facile processes for the controllable fabrication of carbon based nanomaterials,which were then applied in electrochemical sensors and catalyzing water splitting.The relationships between components,structures and performance of the synthesized materials were studied.Details are as follows:(1)In the 2nd chapter,Schiff base metal complex with controllable different shapes and components were obtained on the ITO electrode surface through a one-step electrodeposited process under different experimental conditions.The depositions included nanorod clusters,octahedral-shape particles,cauliflower-like particles and rough spherical particles.The mechanism of the deposited process and nucleated process had been clarified though the studying of the coordinate process,electrochemical process and the components and structures of the depositions.When these depositions used as oxygen evolution catalyst,their performances highly depended on their structures,for which the hexa-coordinate deposition with-OH groups exhibited lower overpotential and higher stability.(2)The 3rd introduced a facile pyrolysis process for paragenesis of palladium-cobalt nanoparticle in nitrogen-rich carbon nanotubes(Pd-CoCNTs).Pd-CoCNTs exhibited efficient catalysis performance for both hydrogen evolution reaction(HER)and oxygen reduction reaction(ORR).Physical characterization revealed that most of the palladium nanoparticles(PdNPs)with dimeters of 2-4 nm were uniformly distributed on the surface of CNTs.Controlled experiments demonstrated that PdNPs provided the surface of CNTs with highly active sites and made the surface more defective,which leaded to a lager electrochemical active surface area(ECSA)and better performance.The activity of Pd-CoCNTs can be adjusted by the content of Pd.At Pd loading of 0.0292 mg cm-2,Pd-CoCNTs toke an overpotential of 0.024 V and 0.215 V to catalyze HER and drive a current density of 50 mA cm-2 in acidic solution,respectively.Compared to the Pd free N-rich CoCNTs,Pd-CoCNTs showed enhanced ORR activity with outstanding methanol tolerance,long-term stability and a similar 4-electron path way.(3)In the 4th chapter,we developed an in situ pyrolysis process for Pd-CoCNTs fabrication without any additional reductant.Physical characterization proved that most of the Pd was existed as independent PdNPs of 3-4 nm,which were uniformly distributed on the surface of CNTs,and only a small portion of Pd was centered at the inner particles with Co to form Pd-Co alloy.Benefitting from the in-situ formed PdNPs,Pd-CoCNTs had a more defective surface with larger ECSA compared to CoCNTs,showing better performance in catalyzing glucose oxidation and hydrogen peroxide reduction.The as prepared glucose sensor displayed remarkable performance with selectivity,stability and reproducibility with a linear range that consisted of two parts,including the former range fitting at 10 ?M-5.3 mM and the later part located at 5.3-23.1 mM,and was successfully applied in the detection of glucose in blood plasma.The calibration line was also fitted for the hydrogen peroxide sensor,containing two parts at 1 ?M-1.11 mM and 2.11 mM-10.1 mM.(4)In the 5th chapter,palladium-carbon hollow nanoparticles(PdHS)was synthesized through a facile template method.Study found that PdHS was consisted of smaller PdNPs.PdHS showed efficient catalytic performance for glucose oxidation.Controlled experiments were conducted in N2-saturated,O2-saturated and air-saturated solution using cyclic voltammetry,respectively.The results demonstrated that,glucose oxidation was in low efficiency in N2-and O2-saturated solution.The oxidation and reduction process of Pd refreshed the PdHS surface and improved its catalytic performance towards glucose oxidation.In high concentration of O2,the surface of Pd was easily oxidized to PdO in positive potential which caused inactivity,however,a competition raised between ORR and glucose oxidation under the negative potential also lowered the efficiency of glucose oxidation.In comparison,PdHS showed best catalytic performance for glucose oxidation in air condition.The calibration line for PdHS based glucose sensor was fitted at 0.2-61.9 mM with a detection limit of 0.07 mM.