Synthesis And Electrocatalytic Oxygen Evolution Performance Of Non-Layered Dysprosium Oxysulfide Based Chainmail Catalyst

The increasingly problem of carbon dioxide emissions needs to be solved by reducing the use of fossil fuels and developing clean energy.Hydrogen energy is considered as an ideal substitute for fossil energy because of its high combustion heat value and pollution-free products.Electrolytic hydrogen production from water has less pollution compared to traditional chemical hydrogen production,and produces high-purity hydrogen gas,making it a truly environmentally friendly hydrogen production technology.Currently,commercial hydrogen production through electrolysis of water requires the use of precious metals and their oxides as catalysts.Their high cost and low availability limit further development of industrial hydrogen production through electrolysis.Cobalt-based catalysts have the advantages of abundant raw materials and high electrochemical activity,making them an ideal substitute for precious metal catalysts.However,single-component cobalt-based catalysts still have intrinsic disadvantages such as low activity and poor stability,which make direct industrial application difficult.Multicomponent integrated catalysts combine multiple components to form heterogeneous interfaces that utilize synergistic effects between components,providing higher reaction activity and stability than single-component catalysts.Chainmail catalysts have a core-shell structure in which the active centers of the core are encapsulated by the shell,maintaining good stability even in harsh environments over long periods of time.At the same time,the strong interaction between the core and shell can adjust the electronic structure at the interface,accelerate reaction kinetics and enhance the catalytic activity of the material.Rare earth elements can be used as additives or accelerators to adjust the 3d electronic structure of transition metals and improve the catalytic performance.However,conventionally doped rare earth atoms are easily dissolved under conditions of oxidation-reduction or strong acid-base,leading to reduced or even deactivated catalyst activity,seriously affecting the long-term stability of the catalytic process.Here,we synthesized a chainmail catalyst Dy2O2S@Co-800（a core-shell structure with outer layer of dysprosium oxide sulfide and inner layer of cobalt）,by a simple one-step carbonization.Due to the synergistic effect between dysprosium oxysulfide and cobalt,Dy2O2S@Co-800 displays excellent OER performance,with low overpotentials of 225.0±1.0 and 298.7±4.5 m V at0.1 and 1.0 A·cm^-2,respectively,for alkaline OER under industrial conditions（50^oC,6 M KOH）.Moreover,dysprosium is not easily dissolving due to the dysprosium element is connected to sulfur and oxygen in dysprosium oxide sulfide by a strong covalent bond,enabling Dy2O2S@Co-800 to maintain stability for more than 120 hours at 1.0 A·cm^-2.In addition,we used a series of in-situ characterization techniques combined with theoretical calculations to reveal the electron redistribution phenomenon on the true active sites and heterogeneous interfaces of the catalyst during OER.A variety of in-situ/ex-situ characterization techniques,combined with theoretical calculations unveil the real active sites as well as electron redistribution on the interface,which intensify the oxygen intermediates adsorption and facilitate the O2 desorption.This work provides a new way to utilize rare earth elements towards optimizing the performance of electrocatalysts.