Biomass-templated Preparation Of C-Ni/NiO Nanocomposites For Magnetic And Electrocatalytic Properties

Pomelo peel?PP?,corn stalk?CS?and cotton fiber?CF?were used as multifunctional agents?template,reductant,carbon source?,Ni?NO₃?₂·6H₂O as Ni source,H₂O as solvent to to prepare carbon-based Ni/NiO?C-Ni/NiO?by a facile and eco-friendly template-assisted dipping/adsorbing-calcining two-steps method without adding any other chemical reagent.The prepared materials were characterized by SEM,TEM,XRD,XPS,FT-IR and BET techniques to analyze and study the morphology,phase composition,and structure of composites.Finally,the obtained C-Ni/NiO nanocomposites are applied to magnetic materials and bifunctional electrocatalyst.The specific research contents are as follows:1.Analyzing the morphology of the obtained materials has foud that the sample prepared with PP had a flower-like structure,CS was chosen as bio-template to synthesize porous nanosheet structure materials,hollow-fiber shape sample were prepared by using the CF as template,in which the material obtained with CF as a template more perfect replication of its fiber morphology,having special structure and uniform morphology.The material has a high specific surface area and rich pore structure due to its special biological morphology and structure,which not only exposes more active sites but also provides ion channels for the electrocatalytic reaction to accelerate the charge transfer rate and make the target material exhibit excellent electrocatalytic activity.2.The experiment successfully synthesized C-Ni/NiO nanocomposites without adding any other reagents?such as precipitant,reducing agent etc.?by analyzing the phase composition of the obtained materials.The results shows that multiple reactions compete simultaneously in situ during the calcination of the precursor material Ni²⁺/Tp(Ni²⁺absorbed on template)in air atmosphere,such as the full combustion?Tp???CO₂+H₂ O+......?,carbonization of the template?Tp?C?,further combustion?C?CO₂?of as-generated carbon material,the conversion(Ni_ad^2?10??NiO)of adsorbed Ni²⁺to NiO,the reduction(Ni_ad^2?10??Ni⁰)of Ni_ad²⁺to Ni⁰ by the carbonization(^C?-H?C⁰),further oxidation?Ni⁰?NiO?of Ni⁰ to NiO,and so on.Particularly,the contents of Ni and NiO effect the property of sample,which can be rationally adjusted by controlling the amount of template and calcination temperature to improve the performance of the sample.3.The obtained material exhibit magnetic properties due to the formation of metal Ni by phase composition analysis.The effects of calcination temperature and template amount on the magnetic properties of the samples were analyzed by magnetic photo and magnetization curves.It can be found that a suitable calcination temperature?low temperature?and moderate amount of template are beneficial to induce the formation of Ni,and the sample exhibit the excellent magnetic propertie with more Ni content.Comparing the magnetic properties of the best samples from three different biological templates demonstrate that hollow-fiber shape C-Ni/NiO composite display the best magnetic properties?maximum saturation magnetization is 44.08 emu/g?,the porous nanosheet structures sample take the second place,the performance of flower-like material is poor.This may be due to the loose morphology structure of CF is easy to burn and carbonize,which is more conducive to the formation of Ni.On the contrary,the carbonization temperature of tight structure CS and PP is high,which is not beneficial to convert the Ni²⁺to Ni⁰.Therefore,the magnetic property of materials obtained under CS and PP are inferior than under CF.4.The C-Ni/NiO nanocomposites are applied to bifunctional electrocatalyst,which exhibits excellent oxygen evolution?OER?and hydrogen evolution?HER?activity in alkaline electrolyte.The best samples obtained under different biological templates PP-C-Ni/NiO,CS-C-Ni/NiO,CF-C-Ni/NiO obtain a current density of 10 mA cm^-2 requiring overpotentials at 316 mV?OER?and 228 mV?HER?,293 mV?OER?and 179 mV?HER?,276 mV?OER?,and 151 mV?HER?.The excellent electrocatalytic activity of CF-C-Ni/NiO catalytic material is attributed to its special hollow-fiber morphology,larger and more efficient surface area area and outstanding ability of charge transfer.