Synthesis Of Carbon Transition Metal Compound Nanostructures On Electrochemical Properties

Lithium ion batteries(LIBs)have been widely used in portable electronic devices since their first commercialization by the Sony Corporation.They are also considered as an attractive power source for electric vehicles.Carbonaceous materials are commonly used as anode material,but improvement of their gravimetric capacity and safety is still required.We need to develop alternative anode materials with large specific capacities,high rate performance,and long-cycle properties,which are desirable for high-performance LIBs.Ti O2 has attracted great attention as anode materials due to its superior safety,excellent rate and cycle ability,but its conductivity is poor.To improve the performance of Ti O2,we adopted some measures,including nanocrystallization,morphological control,and some combination? which could improve the performance of lithium storage.In addition,Hydrogen(H2)with a high calorific value as a clean and sustainable energy resourse represents an ideal alternative of fossil fuels in future.The noble metal-based catalysts(Pt,Ru,Ir)exhibit the best catalytic performance for electrochemical water splitting.However,the global reserve scarcity and exorbitant price of noble metals limit their extensive usage.At present,the intensive search has been dedicated to replace the noble metal based eletrocatalysts by the non-precious and earth-abundant alternatives.Transition metal sulfides,hydroxides,phosphides,and nitrides have demonstrated their potentials as efficient and durable HER catalysts.Hydroxides have been proved as potential electrocatalysts to promote oxygen evolution reation(OER)due to the intrinsically high activity and large surface area.The main contents are summaried as follows:(1)Development of noble-metal-free catalysts towards highly efficientelectrochemical OER is critical but challenging in the renewable energy area.Herein,we firstly embed Ni Fe LDHs quantum dots(QDs)into expanded graphite(Ni Fe LDHs/EG)via in-situ confined formation progress.The interlayer spacing of EG layers acts as nanoreactors for spatially confined formation of Ni Fe LDHs QDs.The QDs supply huge catalytic sites for OER.The in-situ decoration endows the strong affinity between QDs and EG,thus inducing fast charge transfer.Based on the aforementioned benefits,the designed catalyst exhibits outstanding OER properties,in terms of small overpotential(220 m V required to generate 10 m A cm-2),low Tafel slope,and good durable stability,making it a proming candidate for inexpensive OER catalyst.(2)Searching active and cost-effective bifunctional electrocatalysts for overall water splitting is a vital but challenging task towards clean and sustainable energy sources.Here,mixed metal phosphides of Ni2P-Co P anchored on N-doped graphene(Ni Co P/NG)as efficient and earth-abundant electrocatalysts for water splitting are reported.The large active sites,synergism,and hybridization with N-doped graphene endow Ni Co P/NG electrocatalyst with outstanding oxygen evolution reaction activity which is better than benchmark Ru O2 in alkaline electrolyte,as well as active hydrogen evolution reaction in acidic,neutral,and alkaline solution.Ni Co P/NG has further been employed as both anode and cathode in a two-electrode alkaline water electrolyzer towards overall water splitting,and a cell voltage as low as1.57 V is needed to generate a current density of 20 m A cm-2.Moreover,the overall water splitting in this two-electrode electrolyzer can be driven by a single-cell AA battery(nominal voltage of 1.5 V),making Ni Co P/NG as the promising efficient cost-effective catalysts for water electrolysis.(3)Nitrogen doped Ti O2 is synthesized by sol-gel method,which is embedded into the expanded graphite layer to form N&Ti O2/EG composite.The interlayer spacing of EG provides a lot of lithium storage space and alleviates the volume effect.Nitrogen doped Ti O2 has good multiplier performance and cyclic stability.It is combined into a composite material as lithium ion anode material,which effectively improves its specific capacity,ratio performance and cyclic stability.Under0.1 A g-1,the discharge specific capacity is up to 400 m Ah g-1,and the discharge specific capacity is stable at 309.5 m Ah g-1 after 100 cycles,indicating its good cycle stability.Under 5 A g-1,the discharge capacity of the material is 183.7 m Ah g-1,which shows good rate performance.