Controllable Preparation Of Supported Transition Metal Electrocatalysts And The Application For Electro-Oxidation Performance

As the excessive consumption of fossil fuels,energy crisis and environmental problems are becoming more and more serious.Developing clean renewable energy has been the key to solve this problem.Hydrogen energy is attractive as one of the alternatives to traditional fossil fuels owing to its high energy density and environmental friendliness.Among all the hydrogen-producing technologies,electrochemical water splitting for the production of hydrogen has emerged as an efficient and simple hydrogen production technology.However,the slow kinetics of anodic oxygen evolution reaction（OER）is a problem that needs to be solved if the technology is to achieve mass production of hydrogen fuel.To solve this problem,on the one hand,researchers are devoted to develop efficient and low-cost OER electrocatalysts.On the other hand,the researchers replaced the anode OER by electrooxidation of small molecules with rapid chemical reaction kinetics.Of course,this is inseparable from excellent performance,low-cost and good stability of electrocatalysts.Among many electrocatalysts,transition metal-based electrocatalysts not only have the advantages of simple synthesis process,earth-abundant and low-cost,but also have the advantages of high structural controllability,high catalytic performance and excellent stability.In addition,the charge transfer ability of the electrocatalyst can be enhanced if it is loaded on the conductive carrier,which can further optimize the catalytic activity of the catalyst.In this thesis,the author has developed several transition metal based electrocatalysts supported on conductive carbon carriers or nickel foam（NF）substrates.It was applied to catalyze OER or glycerol partial oxidation reaction.The main contents of this thesis are as follows:1.The author fabricated a series of Co-based nanocatalysts embedded in porous N-C skeleton with various degree of sulfurization,and systematically investigated the OER behavior of the nanocatalysts with surface sulfurization,partially sulfurization and fully sulfurization.Detailed investigations proved that the structural benefits of the partially sulfurized Co-based nanocatalyst could lead to excellent activity towards OER catalysis.The partially sulfurized catalyst could display boosted pre-oxidation reaction and facilitated charge transfer behavior,therefore leading to rapid accumulation of the high-valence active species for efficient OER catalysis with remarkable intrinsic activity.In addition,the partially sulfurized Co-based nanocatalyst has strong OER electrocatalytic stability due to the protective effect of the N-C supporting framework.Therefore,the overpotential of the partially sulfurized Co-based nanocatalyst is only 225 m V when the current density is 10 m A cm^-2,and its excellent OER catalytic activity can be stable for about 300 hours.2.A high-entropy layer hydroxide（HE-LH）supported on nickel foam substrate was synthesized by one-step hydrothermal method.And the HE-LH was used to electrocatalyze glycerol partial oxidation reaction to produce formic acid.The high roughness two-dimensional ultra-thin nanosheet structure of HE-LH electrocatalyst can promote the preferential exposure of a large number of surface active sites.Meanwhile,the synergistic action of Fe,Cr,Co,Ni and Cu in the catalyst can optimize the electronic structure,which can further enhance the intrinsic activity of the catalyst.In addition,the high conductivity of NF substrate can promote charge transfer,which can cooperate to optimize the intrinsic activity of the active site of catalyst.Based on this,the HE-LH electrocatalyst not only has the excellent electrocatalytic activity of glycerol partial oxidation reaction,but also has high Faraday efficiency and selectivity of electrocatalyze glycerol partial oxidation reaction to produce formic acid.In addition,the catalyst also showed excellent stability in the electrocatalytic process of glycerol partial oxidation reaction to produce formic acid.Therefore,this method provides a feasible guidance for the production of formic acid by glycerol upgrade oxidation with high-entropy materials.