Electrocatalytic Oxygen Evolution Property And Large-scale Preparation Of Hollow Multishell Nickel-based Materials

Oxygen evolution reaction(OER),as one of the key reactions for metal-air battery,fuel cell and water splitting reaction,play a key role in the fields of energy storage and conversion.However,the OER process involves the transfer of 4 electrons,so the kinetics is very sluggish.The adoption of electrocatalysts can reduce the overpotential of OER.Hollow multishelled structure(HoMSs)materials can expose a large effective surface,enrich reactant molecules,accelerate the mass transfer,and shorten the electron transport path,which makes them very attractive as OER electrocatalysts.The spray drying not only has a simple process and a larger output,but also can accurately control the ratio of each component of materials.In this paper,the spray drying was adopted to prepare LaCo1-xNixO3-δ HoMSs and NiO-CeO2-δ HoMSs through atom substitution and construction of heterogeneous composite structure.In addition,the defect structure and microstructure of the materials were regulated to improve the OER performance.Based on the characteristics,the improvement of the concentration as well as the efficiency of atomization and drying for the precursor solution were accurately studied to achieve the large-scale preparation of HoMSs materials.The main contents are listed as follows:(1)A series of LaCo1-xNixO3-δ HoMSs with different Ni substitution amounts(x,x=0.1,0.3,0.5,0.7,0.9)were prepared by spray drying.As the Ni substitution increased,the overpotential and Tafel slope of LaCo1-xNixO3-δ HoMSs first decreased and then increased.When the Ni substitution amount is 0.5,LaCo0.5Ni0.5O3-δ HoMSs has the smallest overpotential(330 mV@10 mA/cm2)and the smallest Tafel slope(59 mV/dec).The Ni substitution regulates the oxygen vacancies and lattice distortion in HoMSs,thus improving the charge transfer capability,increasing the active surface,and reducing the crystal field splitting energy,resulting in the improvement of OER performance.Meanwhile,the construction of the HoMSs can also increase the effective specific surface area,enhance charge transport and mass transport,thus further improving the OER performance.Finally,the pure perovskite phase HoMSs including La0.9Ce0.1CoO3,LaCo0.9Mn0.1O3 and La0.9Ce0.1Co0.5Ni0.5O3 were also prepared successfully.(2)CeO2 with excellent oxygen storage-exchange capacity and NiO with excellent surface activity were used to construct a heterogeneous composite structure NiO-CeO2-δ HoMSs by spray drying.It turned out that as the proportion of CeO2 increases,the overpotential and Tafel slope of NiO-CeO2-δ HoMSs first decreased and then increased.When the proportion is 0.3,the NiO-CeO2-δ HoMSs has the best OER performance.This is mainly because the construction of the heterogeneous composite structure NiO-CeO2-δ HoMSs not only increases the specific surface area,but also introduces oxygen vacancy defects,thus improving the interface charge transfer capability of the materials and further improving the OER performance.However,the increase of the calcination temperature will induce the decay of the OER performance of NiO-CeO2-δ HoMSs,which is mainly due to the decrease of the specific surface area,reduction of oxygen vacancy defects,and interface charge transfer capability.Based on the above research,a series of heterogeneous composite HoMSs such as Ni/Co,Mo/Ni,Al/Ni and Fe/Ni were successfully constructed by spray drying,which enriched the diversity of HoMSs.(3)The unique advantages of HoMSs make them promising in many application fields.In order to realize the commercial application of HoMSs materials,it is crucial to improve their yield.The spray drying has many advantages in improving the yield of HoMSs.Firstly,the precursor solution of nickel-based HoMSs was successfully prepared through analyzing the preparation process of the spray drying.Then the NiO@Ni@NiO HoMSs with a sandwich structure was prepared.However,the precursor solution can not be completely atomized and dried after increasing its concentration.By adding ammonia and ammonium citrate,the concentration of the precursor solution is improved.Meanwhile,a large-scale spray drying equipment with multiple nozzles was designed to improve the efficiency of atomization and drying for the precursor solution.Thus,the large-scale preparation(kilogram-scale)of NiO@Ni@NiO HoMSs was finally successfully realized,which laid the foundation for the practical application of HoMSs materials.