Preparation And Electrocatalytic Performance Of Metal Selenides Derived From Prussian Blue Analogues

Environment pollution and energy crisis caused by traditional energy forms have imposed many negative influences on humans.Hydrogen,as a kind of novel energy,develops fast in recent years.Besides,electrochemical water splitting has aroused wide interests due to its highly efficient,clean,and easily operated features,hence,developing highly efficient catalysts with low cost is an urgent task.Among all the noble metal free electrocatalysts,metal selenides,with the unique electronic structures,exhibit excellent electrocatalytic performances.In this study,with Prussian blue analogues?PBA?as the precursors,we fabricated a series of transition metal selenides with different components via hydrothermal and calcination methods,and then investigated their HER and OER performances in 1.0 mol/L KOH solution.Hydrothermal methods were used to achieve the selenization of PBA.Morphological and compositional characterizations revealed the presence of Co-Co PBA derived CoSe hollow nanocubes and Ni-Co PBA derived NiSe nano-spheres.In contrast,the selenization of Zn-Co PBA,Fe-Co PBA and Co-Fe PBA formed nanoparticles with two phases.The growth mechanism of CoSe and NiSe indicates that Se^2-would conduct ion-exchange reactions with[Co?CN?₆]^3-from PBA and then form MSe.In the ion exchange process,thanks to the different diffusion rates of Co²⁺,Ni²⁺and Se^2-inward and outward caused by their different radiuses,the CoSe hollow structures and NiSe nano-spheres could be formed.In 1.0 mol/L KOH solution,for HER,at the current density of10 mA/cm²,CoSe and NiSe achieve the overpotentials of 315 and 372 mV,with the Tafel slopes of 171 and 183 mV/dec,respectively.For OER,CoSe and NiSe have the overpotentials of 337 and 356 mV,with the Tafel slopes of 56 and 60 mV/dec.The overpotentials of other selenides are higher than those of CoSe and NiSe.To better control the morphologies and compositions,we used solid phase calcination method to prepare selenides.Their components can be expressed as CoSe₂?Ni_0.6Co_0.4Se₂?CoSe₂/ZnSe?Fe_0.6Co_0.4Se₂ and Fe_0.4Co_0.6Se₂,most materials can inherent their pristine morphologies.We conducted OER under 1.0 mol/L KOH solution,it was found that at the current density of 10 mA/cm²,they have the overpotentials of 355,327,351,334 and 300 mV,respectively,which are much better than those of metal oxides(Co₃O₄?Co₃O₄/NiO?Co₃O₄/ZnO?Fe_1.8Co_1.2O₄?Fe_1.2Co_1.8O₄).In addition,the performance of Fe_0.4Co_0.6Se₂ even exceeds that of IrO₂,and it also has excellent durability,which may because that doping of Fe can induce the synergistic effects between two metals and facilitate OER process.