Synthesis Of Cobalt Phosphide-Based Heterostructured Catalysts And Their Water Splitting Performance

Considering the growing problems of global fossil energy crisis,environmental pollution and greenhouse gas emissions,the demand to explore clean and sustainable energy sources has become more and more urgent.Hydrogen has the advantages of high energy density and no pollution,and the use of hydrogen instead of fossil fuels can mitigate the greenhouse effect.High purity hydrogen can be produced by electrolysis of water,which is clean and non-polluting,offering significant advantages in future development.Efficient electrocatalysts can reduce the electrolytic water reaction overpotential and hence reduce energy losses.Pt-and Ru-based materials are the most efficient electrocatalysts to facilitate the cathodic hydrogen evolution reaction（HER）and anodic oxygen evolution reaction（OER）of electrolytic water.However,the scarcity and expensive price of these noble metals limit their large-scale practical applications.In this paper,cobalt phosphide-based materials are used as research objects,and improvements are made in terms of morphological structure modulation and heterostructure interface engineering to prepare catalysts with the best HER/OER activity.The main research contents and results of this thesis are as follows.（1）Using phosphorous resin and CoCl₂as raw materials,adjusting the feedstock ratio,a series of cobalt phosphide nanoparticles with different cobalt/phosphorus ratios loaded on porous carbon electrocatalysts were successfully synthesized by a simple one-step thermal treatment method.The prepared CoP-Co₂P/NPC heterostructured catalysts have a homogeneous three-dimensional porous structure and large specific surface area,which not only have abundant active sites and ion diffusion channels,but also have high electrical conductivity and strong acid and base resistance,exhibiting excellent HER catalytic activity and stability.It only needs 96.7 and 162.1 m V to achieve a current density of 10 m A cm^-2in alkaline and neutral solutions,the Tafel slopes are only 55.4 and 93.6 m V dec^-1.Besides,it demonstrates potential seawater electrolytic catalytic performance,with small overpotentials(111.2 m V@10 m A cm^-2)and Tafel slope(64.2 m V dec^-1)in alkaline seawater solutions.（2）Based on the excellent HER activity of cobalt phosphide,Co₂P-Co_xO_y/C（Co_xO_y=CoO or Co₃O₄）heterostructure catalysts were successfully constructed by reasonably controlling the reaction temperature and oxidation time to achieve controlled oxidation based on the physical phase and morphology of Co₂P nanoparticles.Porous carbon network loaded Co₂P-Co_xO_ynanoparticles combine both the excellent HER active component of cobalt phosphide with the excellent OER active component of cobalt oxide.The synthesized Co₂P-Co₃O₄/C catalysts exhibited the most superior electrocatalytic activity and stability.In alkaline solution,it only requires 86and 246 m V to reach a current density of 10 m A cm^-2in HER and OER,the corresponding Tafel slopes are only 49.7 and 69.5 m V dec^-1.In addition,when Co₂P-Co₃O₄/C was used as both an anodic and a cathodic electrocatalyst,Co₂P-Co₃O₄/C|Co₂P-Co₃O₄/C only requires a low voltage of 1.55 V to achieve a current density of 10 m A cm^-2,which is even better than Pt/C|RuO₂/C system,and the current density does not decay significantly after 120h of operation.