Controllable Preparation Of Multi-Element Amorphous Metal-Organic Framework Materials And Its Application In Oxygen Evolution Reaction

Electrolyzed water is considered to be one of the most promising hydrogen production methods due to its rich resources,no greenhouse gas emissions,and high efficiency.The electrochemical decomposition of water is mainly composed of two half reactions,the hydrogen evolution reaction（HER）on the cathode and the oxygen evolution reaction（OER）on the anode.The theoretical decomposition voltage of water is 1.23 V,but in order to overcome the thermodynamic equilibrium potential,the actual electrolysis process need to apply a certain overpotential（η）,which will increase energy consumption,high-efficiency electrocatalysts can reduce the overpotential of these catalytic reactions and increase the current density.The precious metals IrO₂ and RuO₂ are highly efficient catalysts for catalyzing OER,but the scarcity and high cost of precious metals hinder their large-scale application.Therefore,there is an urgent need to develop non-noble metal electrocatalysts with high catalytic activity and stability for hydrogen production.At present,amorphous metal organic framework（MOF）materials have also been involved in this field,and most of the materials as new precursors are easier to synthesize advanced electrocatalysts.MOF itself can also be used in electrocatalysis and many water splitting applications.Acts as an effective catalyst material in applications.This paper mainly studies the preparation method,microscopic morphology,electronic structure,valence state and electrocatalytic oxygen evolution reaction performance of multi-element amorphous metal-organic framework materials.The oxygen evolution reaction mechanism of multi-element amorphous metal-organic framework materials is explored.First,the classic cobalt-based MOF was synthesized by a one-step solvothermal method.A series of amorphous bimetallic FeCo-MOF materials（AFC-MOF）were synthesized by doping Fe³⁺ions into the crystalline cobalt-based MOF to make it amorphous.Benefiting from the excellent surface morphology and electrochemical surface area,it greatly promotes the charge transfer in the electrolysis process,and the Fe/CoaMOF（labeled AFC-MOF（1:4））with a synthetic metal ratio of 1/4 shows excellent performance.And stable OER activity,with an ultra-low overpotential（256 m V）at a current density of 10 mA·cm^-2,and a small Tafel slope(42.70 mV·dec^-1).The structure of the material was analyzed by XPS and XAFS,and it was found that the AFC-MOF material is a compound of pure divalent Co and trivalent iron,which has similar structural characteristics to CoO,but also has unique structural advantages.For example,a larger specific surface area,morphological features that are more conducive to electron transport,and the synergistic effect of bimetals.All these fully prove the feasibility of AFC-MOF material as OER catalyst,and amorphous FeCo-MOF material shows better OER activity than crystalline FeCo-MOF material.Finally,the ternary metal FeCo₄U_x material was synthesized by the doping of the high-valent metal element U（Ⅳ）.The introduction of high-valent metal atoms can optimize the energy required for the oxidation cycle of the 3d metal site in the OER process.By adjusting the adjacent metal atoms the electronic structure is expected to reduce the free energy of reaction required for the process,thereby effectively improving the OER activity of the material.