Construction Of Copper-Based Composite Microstructure And Its Catalytic Behavior On Boride System

As a kind of acknowledged clean and efficient new energy,the development and utilization of hydrogen energy are effective tactics to actively respond to the fossil energy crisis and environmental pollution.The establishment of a safe,efficient and controllable hydrogen storage-releasing system is the key link for the rational utilization of hydrogen energy.Ammonia borane（NH₃BH₃,AB）is a complex type hydride solid hydrogen storage material that has attracted attention in recent years.Its theoretical hydrogen content is as high as 19.6 wt%,its physicochemical properties are stable,easy to store and transport,and can Controlled release of hydrogen under conditions.Sodium borohydride（Na BH₄）also has a high theoretical hydrogen content（10.7 wt%）,is a direct hydrogen source for direct sodium borohydride fuel cells,and is also one of the key reactants for preparing AB.As part of the research content of the National Natural Science Foundation of China（No.21576073）,this article aims to improve and optimize the process conditions for the catalytic hydrogen release of ammonia borane,and explore the preparation of sodium borohydride by electrochemical methods.1.Controllable preparation of Pd-Cu micro-nano alloy and evaluation of its catalytic activity.During the preparation of Pd-Cu micro-nano alloys,adjusting the temperature and the amount of additives can control the directional growth of the product to a certain extent,and prepare Pd-Cu micro-nano alloys with different morphological characteristics（such as concave Tetrahedron,cube,polyhedron,nanosphere,nanowire,worm-like,sea urchin-like and peony-like,etc.）,and comprehensively characterize its phase composition and morphology,and evaluate its catalytic activity.The analysis shows that the Pd-Cu micro-nano alloy exhibits an alloy phase structure and has high catalytic activity and selectivity.Due to the charge transfer from Cu to Pd,a synergistic effect is formed,which enriches the electrons around the Pd nucleus,facilitates the adsorption of metal to H to form M-H species,and promotes the catalytic hydrolytic dehydrogenation of AB.In the hydrolysis reaction of 298 K catalyzed ammonia borane,the concave concave Pd-Cu nano-alloy has almost the same catalytic activity as Pd,and its apparent activation energy is 31.18 k J/mol,which can be maintained after 5 cycles of use 89.0%of initial catalytic activity.2.Construction and characterization of TiO₂/TiN nanotube array and its supportedsingle/bimetallic catalytic electrode.（1）Preparation of TiO₂/TiN nanotube array:10.0×10.0×2.0 mm high-puritytitanium plate is selected as the metal substrate for polishing-cleaning-drying surface pretreatment,the TiO₂nanotube array（TiO₂-NTAs@Ti）is grown on the surface of the titanium plate by using secondary anode oxidation method.By gradually optimizing the process conditions,TiO₂nanotubes with a diameter of about 150 nm are obtained,and the nanotubes are arranged in an orderly manner without damage to the nozzle.Put TiO₂-NTAs@Ti in the muffle furnace,subject it to constant temperature treatment in an N₂atmosphere,then pass high-purity NH₃gas,heat up to 850℃,and react for a certain period of time.In the above process,the process preparation parameters were continuously optimized.With the help of XRD,SEM and EDS analysis,it was found that TiN-NTAs@Ti with neat arrangement and large specific surface area was obtained.（2）Preparation of metal/TiN-NTAs@Ti electrode:TiN-NTAs@Ti is used as the electrode substrate,and the non-cyanide copper plating solution of citric acid system and the non-cyanide gold plating solution of chloroauric acid system are respectively used as the plating solution,and the current-time curve method is used Electrodeposition of Cu and Au on the surface of TiN-NTAs@Ti.By changing the electrodeposition time and other conditions,Cu/TiN-NTAs@Ti,Au/TiN-NTAs@Ti and Au（Cu）/TiN-NTAs@Ti composite structure catalytic electrodes with different metal loadings can be obtained.By means of phase and morphological characterization methods（such as XRD,EDS,SEM,etc.）,it can be seen that the Cu particles adsorbed on the electrode surface are spherical.With the increase of electrodeposition time,the particle size and loading of Cu also increase,and there are A part of the copper particles were deposited inside the TiN nanotubes;Au particles were initially in an amorphous shape and crystallized into larger-sized dendrites over time;after analysis,it was believed that the electrodeposition time for copper was 40min and the electrodeposition time for gold The best time is 1 min,that is,the electrode has a higher specific surface area and more catalytic active sites.3.Electrocatalytic behavior of metal/TiN-NTAs@Ti composite electrode on metaborate.The electrochemical behavior of the M（Cu,Au）/TiN-NTAs@Ti electrode in potassium ferricyanide solution was tested by cyclic voltammetry.Its redox peak potential difference was less than 80 m V,confirming that the electrode has a low Internal resistance and high electrochemical reversible stability.A three-electrode system was constructed with Au（Cu）/TiN-NTAs@Ti electrode as cathode,graphite electrode as anode,and saturated calomel electrode as reference electrode.The electrocatalytic reduction of Na OH solution and alkaline sodium metaborate solution at a certain concentration were studied respectively.By adjusting the electrochemical process conditions（electrolysis voltage,pulse ratio and electrolysis time,etc.）,the effect of cathode electrochemical reduction under different conditions was investigated.Linear voltammetry and chemical analysis were used to monitor and analyze the electrode reaction process and its product,and reasonably speculate on the electrode process and its reaction mechanism.