Design And Investigation On Cobalt Based Self-supported Catalyst For The Performance Of Oxygen Evolution Reaction In Electrochemical Water Splitting

Electrochemical water splitting is an efficient strategy to produce high-purity hydrogen（H₂）.However,the oxygen evolution reaction（OER）that occurs at the anode involves a complex four-electron transfer process,which is the rate-determining step of overall water splitting.For OER,the catalyst plays crucial roles in reducing the overpotentials and thus improving the electrocatalytic performance.Transition metal cobalt based materials,such as oxides,hydroxides and various composites,are promising OER catalysts.In addition,when the catalysts in-situ grow on conductive substrate,the resistance at catalyst/electrode interface can be reduced,further enhancing the catalytic performance.Based on above analyses,in-situ growth of Almodified Co LDH nanosheets（NSs）on carbon cloth（CC）and ternary CoNiAl_xO/NF nanowires（NWs）were well designed.The main contents are as follows:（1）A series of Al³⁺-doped Co LDH/CC catalysts were synthesized by one-step hydrothermal method using CC as the substrate and controllable Co and Al salts as raw materials.The optimized Co₂Al₁ LDH/CC exhibits excellent electrocatalytic OER performance and good stability in both alkaline and neutral electrolytes,characterized by the low overpotentials of 171 and 200 mV at current density of 10 mA cm^-2,respectively.Experimental results and theoretical calculations indicate the excellent OER activity of Co₂Al₁ LDH/CC can be attributed to the following three aspects:（ⅰ）the high conductive substrate of CC improves the conductivity and accelerates the electron transfer and mass transport processes;（ⅱ）the self-supported structure and the selective growth of Co and Al results in ultrathin nanosheets structures which provide abundant active sites;（ⅲ）the low content of introduced Al³⁺ can effectively tune the d-band center of the Co LDH/CC,which in turn reduces the Gibbs free energy of the OER intermediate on the catalyst surface.This work provides an idea for optimizing electrocatalysts for LDH by modulating the morphology and electronic structure.（2）Using NF as both conductive substrate and Ni source,an electrocatalyst(CoNiAl_0.5O-300/NF)with excellent OER performance was designed and synthesized through a two-step process.In 1 M KOH,CoNiAl_0.5O-300/NF exhibited a lower overpotential（230 mV）at a current density of 100 mA cm^-2,a smaller Tafel slope of 26 mV dec-1,and excellent stability which can last for 180 h at current density of 10 mA cm^-1.The high conductive and porous structure of the NF substrate not only can increase the overall conductivity,provide abundant reaction active sites,but also promote the penetration and diffusion of the electrolyte,which are conducive to charge transfer and mass transport.What’s more,the introduced Al³⁺ not only facilitates the reaction of the Ni source in the NF to transform into nickel oxide,but also promotes the transfer of electrons from Ni to Co.In addition,the electrophilic O^-/O₂^2- generated on the catalyst surface has high adsorption activity,which is helpful for water oxidation in alkaline solution.This study provides a new solution for designing low-cost,high catalytically active electrocatalysts.