Synthesis Of Non-precious Metal-based Selenides Catalyst And Its Electrochemical Properties Of Alkaline Oxygen Evolution Reaction

With the gradual increase of global pollution,there is an imminent need for the development of clean energy,and hydrogen energy is undoubtedly a very ideal clean energy source,of which electrochemical water splitting technology is considered to be an effective means of hydrogen production.Among them,the anodic oxygen evolution reaction（OER）is considered the rate-determining step of water splitting,so the development of non-precious metal-based OER catalysts with low cost and excellent performance is important to control the application cost of hydrogen energy.Among the various catalysts,transition metal selenides have a narrow energy band gap and metallic properties,and excellent acid and base resistance,making them a promising catalyst for OER in 1.0 M KOH solution.Based on this,this dissertation selects transition metal selenides as the research objects,improves the synthesis method,and modulates the structure and composition of the materials in order to improve their electrocatalytic performances and stability,and has achieved the following results:1.Based on the high electronic conductivity of conductive carbon fiber,we synthesized a P-doped porous catalyst(Ni_xCo_1-xSe_y-P)in situ on carbon fiber.The OER catalytic performance of different samples was tested in 1.0 M KOH solution,and the electrochemical measurements results showed that the P-doped Ni_xCo_1-xSe_y-P electrode had the highest catalytic activity.The required overpotential(₁₀₀)at a current density of 100 m A cm^-2 was 436.0 m V with a Tafel slope of 64.3 m V dec^-1,while the₁₀₀ increased by～16 m V after 1000 CV cycles.The electrochemical impedance spectrum（EIS）indicates that the Ni_xCo_1-xSe_y-P electrode exhibits small charge transfer resistance,which indicates that the phosphorus doping has improved both the electron transport rate and the electrocatalytic performance of Ni_xCo_1-xSe_y-P.2.To simplify the catalyst synthesis method,cobalt diselenide submicron particle catalysts were successfully synthesized using an atmospheric pressure solvothermal method by adjusting the volume ratio of ethylene glycol and deionized water to control the sample morphology.Where the cobalt diselenide particles（Co Se₂-5:5）with a volume ratio of 5:5 correspond to an overpotential(₁₀₀)of 382.0 m V at a current density of 100 m A cm^-2 in 1.0 M KOH.The sample also exhibited excellent cyclic stability,with₁₀₀ increasing by～28 m V after 5000 CV cycles,an increased rate of only 7.3%.After comparing with the overpotential and Tafel slope of other cobalt-based OER catalysts in the literature,it was found that the sample prepared using the simplified synthesis method still had a good catalytic performance.3.Afterwards,the synthesis method was further simplified by using cheap pure water as the reaction system and L-cysteine as the structure-directing agent,and Ni Se₂-L submicron particles with coral-like morphology were successfully synthesized as OER catalysts by atmospheric pressure hydrothermal method,and the hydrothermal reaction time was further compressed to 4 h.The average of₁₀₀ in 1.0 M KOH was 400.3 m V and 522.3 m V,respectively.In addition,the Ni Se₂-L electrode exhibited excellent stability,with₁₀₀increasing by～16 m V after 5000 CV cycles,and was able to keep steady for 10 h at a current density of 40 m A cm^-2 with a current density decrease of 5.26 m A cm^-2.The relevant experimental results indicate that the added L-cysteine as a ligand interacts with the specific crystal planes of Ni Se₂ through free amino and carboxyl groups,and coordinates with free Ni²⁺to modulate the morphology of the sample and expose more active sites.