Synthesis And Electrochemical Properties Of MOF-based Cobalt Phosphide/Sulfide Catalysts

Transition metal compounds have excellent catalytic and electrochemical properties,and we expect they can be widely used in catalysis and energy storage and conversion in future.In this paper,cobalt phosphide and cobalt molybdenum sulfide were synthesized based on MOF and the effects of different reaction conditions towards the performance of synthesised catalysts were studied.By changing the ratio of ZIF-67s and sodium hypophosphite,a series of CoP hybrids with various morphologies were successfully synthesized by utilizing MOFs as precursors,sodium hypophosphite as phosphorus source.The phosphating method we adopted was low-temperature phosphorization.As HER catalysts,the activity of these CoP hybrids increased at first and then decreased with the increasing of phosphorus source.When the ratio of Co to P was 1:15,the activity of CoP hybrid we obtained was the best.This CoP hybrid we obtained is the structure of CoP nanoparticles embedded in P and N co-doped carbon?CoP@PNC?.CoP@PNC not only exhibited good HER and OER activity and stability in alkaline environment,but also showed excellent HER performances in acidic environment.The results of DFT calculation and conductivity mesurement showed that the CoP@PNC has good conductivity,which benefited the electron transfer and then enhance the improvement of catalytic activity.Further,using nickel foam as substrates,CoP@PNC acted as a superior catalyst to catalyze overall water splitting and only required a voltage of 1.52V to deliver a current density of10mA/cm²,superior to the noble-metal catalysts system?Pt/C//IrO₂?and the reported noble-metal-free bifunctional electrocatalysts.By using ZIF-67s as precursors and the thioacetamide as sulfur source,CoS nanomaterials can be synthesized through solvothermal method.In order to improve the electrochemical activities,we added molybdenum when preparing precursors,and then the cobalt molybdenum sulfide can be obtained.By adjusting the ratio of Co and Mo,solvothermal temperature,and solvothermal time,we explored the influence of various factors on the catalyst and finally acquired the best reaction condition.The material exhibited excellent HER activity and stability in acidic environment and required a voltage of-158mV to deliver a current density of 10 mA/cm².