Controllable Preparation And Electrocatalytic Properties Of Ni Foam Supported Mesoporous Carbon Doped Metal Phosphide Multifunctional Catalyst

In order to deal with the increasingly serious environmental pollution and energy depletion in the world,reserachers began to work on clean and green electrochemical energy storage devices,such as zinc-air batteries,electrolytic water.Zinc-air battery has attracted much attention because of its high theoretical energy density and clean alkaline electrolytic water.However,as the important reactions in these devices,oxygen evolution(OER),oxygen reduction(ORR)and hydrogen evolution(HER),the reaction kinetics of the three reactions are relatively slow,which hinders the development of these green and clean electrochemical energy storage devices.At present,the commercial catalysts with better OER performance are the ones with better Ir O2,Ru O2,ORR and HER performance,and the ones with better Pt/C.However,these catalysts are noble metals with scarce content and high price in the world.Therefore,in order for these electrochemical devices to be commercialized on a large scale,we need to develop low-cost and efficient three-functional catalysts.This paper mainly use the nickel foam for conductive base,the design of porous carbon and nickel chemical compound,and then phosphorus source,introduced by high temperature calcination,prepared by coprecipitation method and hydrothermal method for porous with flowers shape classification of nano structure of nitrogen mesoporous carbon doped nickel phosphide catalysts,and through a series of various samples of these physical characterization and electrochemical testing,physical characterization,such as scanning electron microscopy,transmission electron microscopy,X-ray diffractometer,X-ray spectrometer,electrochemical testing,such as linear scanning voltammetry,blue-electric system and other methods,mainly to analyze the morphology of the samples,crystal surface,electronic configuration,and elemental valence,electrochemical performance and catalytic principle.We can draw a few conclusions:A series of Nix Py@NF catalysts under different hydrothermal conditions and phosphating temperatures were prepared by a simple hydrothermal phosphating method,and the optimal electrochemical performance of Nix Py@NF catalyst under appropriate conditions was explored.Finally,through the physical characterization of samples and electrochemical tests under various conditions,it was found that the Nix Py@NF catalyst showed the best OER performance and stability at 120 oC,14h hydrothermal conditions and 320 oC phosphating conditions.The results of electron microscopy showed that Nix Py@NF catalyst was essentially a kind of porous hierarchical nanosheet,which was assembled into a flower cluster morphology.This structure would essentially expose more active sites,which would facilitate efficient electron transport.Nix Py@NF is obtained by XRD and XPS analysis between different valence state phosphating nickel catalyst activity is derived from the heterostructure,and HRTEM is one of the amorphous structures and phosphate crystallization area of nickel element closely connected and there is no obvious boundary,thus this is an area of amorphous phosphate to the OER catalytic reaction has played a good protection effect.In addition,electrochemical tests show that Nix Py@NF catalyst shows excellent bi-functional electrocatalytic activity and stability in HER and OER in alkaline solution,in which the current density of 10 m A cm-2 can be reached with only 76 m V in HER reaction.In the OER reaction,only 240 m V overpotential is needed to reach the current density of 10 m A cm-2.Through the above analysis,we found that this excellent catalytic performance is actually due to the appropriate thickness of amorphous structure designed under specific hydrothermal conditions and the heterogeneous interface between different valence states of nickel phosphide.By taking advantage of the good OER performance of catalyst in above,we introduced porous carbon with good ORR performance into it,and prepared the tri-functinal Nix Py-N-HPCs@NF catalyst on nickel foam by coprecipitate method and hydrothermal phosphorization method.This heteroatom-rich product has different co-ordination forms and significant coordination capacity,which can bind N and P atoms into the carbon-nickel matrix during calcination,and the nickel metal component of the precursor is slowly reduced into the nickel phosphide phase,and then in-situ embedded into the carbon-nickel matrix co-doped with nitrogen and phosphorus.Nix Py-N-HPCs@NF catalyst reached the current density of 10 m A cm-2 in OER with an ultra-low potential of only 1.47 V,i.e.Ej10 was 1.47 V,which was lower than the 1.67 V of the commercial catalyst Pt/C-Ru O2.Nix Py-N-HPCs@NF has a half-wave potential(E1/2)of 0.81 V in ORR,which is close to the performance of the commercial catalyst Pt/CRu O2.In HER,only 86 m V of overpotential is needed to reach the current density of 10 m A cm-2,which is far lower than the 302 m V of Pt/C-Ru O2.The stability of Nix Py-N-HPCs@NF in OER was analyzed by quasi-situ characterization method.It was concluded that the morphology of the catalyst changed obviously during the whole catalytic process.It was believed that the change of the surface morphology of the catalyst and the gradual oxidation of the carbon layer were the real reasons for the degradation of the catalyst performance.Therefore,the construction of stable outer carbon layer can avoid the oxidation of internal active metal compounds,and the unique interconnecting porous structure of the catalyst can slow down the oxidation rate of outer porous carbon,effectively avoid the rapid transformation of internal active center,thus showing good catalytic stability.On the basis of the above,we applied these catalysts to actual electrochemical equipment,water electrolytic equipment and zinc-air battery.The Nix Py@NF catalyst used in alkaline water splitting device 1.72 V to reach the current density of 10 m A cm-2,and its activity is mainly attributed to the heterogeneous structure between different valence states of nickel elements.The high power density of 377 m W cm-2 can be achieved when Nix Py-N-HPCs@NF catalyst is directly used as the cathode catalyst for zinc-air battery assembly,while the current density of 10 m A cm-2 can be achieved with only 1.52 V low voltage when it is applied to alkaline water splitting.The above results further indicate that the two Nix Py based catalysts/electrodes designed in this paper have certain application potential,providing data support and theoretical basis for the development of Nix Py based multifunctional catalysts.