Construction Of High Stability Active Catalyst And Study On Catalytic Performance Of Hydrogen Production

Sodium borohydride hydrolysis is a fast and efficient means of hydrogen production,requires highly effective catalysts.Noble metal catalyst is an excellent catalyst for sodium borohydride hydrolysis with high catalytic activity.The non-precious metal catalyst is based on cobalt,and the cost is low.But both have the problem of poor stability.In order to improve the catalytic efficiency and cycling performance of the catalyst,three nano-composite catalysts,Co-Ti4N3,Ru NPs-TiO2-Ti3C2 and Ru@Co-Ni@NF,were prepared by using different metal frame structures as supports.The main research contents are as follows:(1)There are a large number of groups on the surface of MXene that can attract metal cations.Ti4AlN3 is etched with HF to obtain accordion-like Ti4N3Tx.The structurally stable cobalt nanorods were anchored to Ti4N3TX by hydrothermal synthesis.Ti4N3Tx effectively prevented agglomeration of cobalt nanorods and the lamellar structure made full contact between the solution and the active site of the catalyst.The Co-Ti4N3 composite has good activity and stability for the hydrolysis of sodium borohydride,with a hydrogen yield of 526 mL·min-1·g-1 and an activation energy of 44.23 kJ·mol-1 at 30℃.The catalyst retained 75%of its initial activity after 15 cycles,which is much higher than previously reported results.Density Functional theory(DFT)calculation shows that the Gibbs free energy of Co-Ti4N3 adsorbed hydrogen is close to 0 eV,which further confirms that Co-Ti4N3 has good activity.(2)In order to improve the atomic utilization rate of noble metal Ru,TiO2 nanospheres containing oxygen vacancies were grown on the layered Surface of Ti3C2Tx,and Ru NPTiO2-Ti3C2 catalyst was prepared by fixing ultrafine Ru nanoparticles on the surface of TiO2 nanospheres by calcination of hydrogen reducing ruthenium precursor.X-ray photoelectron spectroscopy confirmed the presence of titanium in a low oxidation state and thus the presence of oxygen vacancies.The spherical aberration transmission electron microscopy(TEM)image shows that the homogeneous Ru nanoparticles(average diameter about 2 nm)are dispersed on TiO2,and a small part of Ru exists in the form of single atom.The optimal mass fraction of Ru was 0.33%(the hydrolysis rate of sodium borohydride at 303 K was 60 L·min-1·gRu-1).In addition,the catalyst showed good activity even after 5 cycles.(3)Nickel foam is a kind of cheap,stable,hollow and porous carrier material.The nickel-cobalt Layered Double Hydroxide was coated on the nickel foam framework by a one-step hydrothermal process.The ruthenium was etched on the surface of cobalt-Nickel Layered Double Hydroxide by impregnation method.Finally,the ruthenium was reduced in situ by NaBH4 solution to prepare Ru@Co-Ni@NF Foam composite catalyst.The content of Ru in the sample was 1.27 wt%by ICP analysis.XPS results confirmed the existence of ruthenium.It was found that the catalytic performance of the catalyst could reach 38 L·min1·g-1 at 30℃ when the molar ratio of cobalt to Nickel was 1:2,this is due to the skeleton structure of the nickel foam and the support of a highly active catalyst.Thanks to the nickel foam skeleton structure,the catalyst retained 72%of its initial activity after 10 cycles applications.