Construction Of CoMoO₄-Based Composite Electrocatalysts And Their Applications In Electrocatalytic Water Splitting

As a typical transition metal oxide,owing to the stable crystal structure,strong redox ability and great conductivity of cobalt molybdate（CoMoO₄）,it has a broad application prospect in the field of electrocatalytic water splitting.However,the further practical applications of CoMoO₄ are restricted by its low utilization rate of active sites and short cycle life to a large extent.In order to make up for the above defects,this paper constructed CoMoO₄-based heterostructure nanocomposite,taking advantage of the synergetic effect between different electrode materials to reduce the reaction kinetic energy barrier of water splitting,increase the specific surface area,improve the stability,and then enhance the electrocatalytic activity.The component,microstructure,electrocatalytic activity and stability of the as-prepared samples were investigated by a series of characterization.Furthermore,the process of electrocatalytic water splitting was also discussed.The specific research content was as follows:1.Novel CoMoO₄-Ni（OH）₂ nanosheet array composite electrocatalysts were successfully synthesized by facile hydrothermal and electrodeposition methods supported on Ni foam.In order to find the best composite ratio,the loading amount of Ni（OH）₂ nanosheets can be well controlled by changing the deposition time.The electrocatalysts were characterized by XRD,XPS,SEM,TEM and BET,and the results showed that there is a strong interfacial effect between CoMoO₄ nanosheets and Ni（OH）₂ ultrathin nanosheets.A series of electrocatalytic tests were conducted in 1 M KOH solution by using a three-electrode configuration.The relevant results showed that the optimized CoMoO₄-Ni（OH）₂-400s electrocatalyst manifests the excellent oxygen evolution reaction（OER）catalytic performance with a low overpotential of 349mV at the current density of 100 mA cm^-2,a long-term stability,and high（nearly 100%）Faradaic efficiency.According to the electrocatalytic oxygen evolution mechanism,it was found that the oxidation of Ni²⁺and Co²⁺have created a synergistic effect to lower the energy barrier for the OER,which contributes greatly to the high electrocatalytic activity.2.A novel integrated ternary hybrid（CoO_x/CMO）composed of CoO/Co₃O₄（CoO_x）nanoparticles supported on CoMoO₄ nanorods（CMO）was constructed through the hydrothermal treatment of ZIF-67/CoMoO₄ followed by a thermal annealing.The as-prepared samples were characterized by XRD,XPS,BET,SEM and TEM,and the corresponding electrochemical measurements were conducted in 1 M KOH solution.Benefiting from the enlarged surface areas,more active sites and fast charge transfer kinetics on the interface between CoO_x and CMO,CoO_x/CMO electrocatalyst manifests the excellent OER catalytic performance with a low overpotential of 253 mV at the current density of 10 mA cm^-2 and high long-term durability.It can be found that the well-coupled interface between CMO and cobalt oxides has facilitated the charge transfer and reactant transport and accelerated the action,thus leading to enhancement of OER performance.3.Novel CoP₃/CoMoP heterogeneous nanosheet arrays supported on nickel foam（CoP₃/CoMoP/NF）were synthesized from a one-pot phosphidation of CoMoO₄nanosheet arrays.The phase and microstructure of as-prepared samples were tested by XRD,XPS,SEM,TEM and BET characterization,indicating the strong interaction between CoP₃ particles and CoMoP nanosheet.The electrocatalytic hydrogen evolution performance of CoP₃/CoMoP/NF was investigated in different media,which exhibited excellent activities with a low overpotential of 125 mV to reach the current density of10 mA cm^-2 in the acidic media.Furthermore,the CoP₃/CoMoP/NF showed high electrocatalytic hydrogen evolution reaction（HER）activities and durability in both neutral and alkaline media.It can be found that plenty of tiny CoP₃ nanoparticles were embedded in the CoMoP nanosheet,forming abundant heterostructure interface,which can provide more active sites and improve the electric conduction,consequently improving the catalytic efficiency.