Catalyst Preparation Of Ruthenium Supported On Ceria And Their Application In Hydrogen Production From Ammonia Borane Hydrolysis

Hydrogen is a promising energy carrier that can be expected to replace unsustainable and CO₂-emitting fossil fuels in the future.Ammonia borane（NH₃BH₃,AB）has attracted extensive interest due to its high hydrogen capacity and low molecular weight.AB hydrolysis to produce hydrogen can be achieved without the need of high temperatures.In this work,using ruthenium（Ru）metal as the active species and metal oxide（i.e.,CeO₂）as carriers,three different catalysts were prepared by loading Ru nanoparticles onto CeO₂ with different composition using two different reduction methods.The main work is as follows:（1）Nano-cube CeO₂ can be obtained by hydrothermal synthesis and the Ru/CeO₂-H₂/Ar catalysts were prepared by loading of Ru nanoparticles onto the surface of nano-cube CeO₂through reduction using H₂/Ar gas mixture.It was demonstrated that the use of suitable reduction methods was beneficial to the formation of small particle size and uniform dispersion of Ru nanoparticles.Therefore,the turnover frequency（TOF）of Ru₁/CeO₂-H₂/Ar was 176.9 mol _H2·mol _Ru^-1·min^-1 and the activation energy（E_a）was 42.98 k J·mol^-1 at room temperature（25°C）for AB hydrolysis.（2）Nano-cube CeO₂ with Co doping was prepared by a simple hydrothermal process to form the Ru/Co-CeO₂ catalysts.The introduction of Co could result in the formation of a Co-O-Cespecial structure on the surface of CeO₂ and a synergistic effect with Ru,giving rise to a large enhancement of AB hydrolysis performance of Ru₁/Co-CeO₂-2 with a TOF value of384.5 mol _H2·mol _Ru^-1·min^-1 and an E_a of 45.96 k J·mol^-1.（3）Co@NPC was prepared by high temperature calcination of ZIF-67 as precursor to obtain Co@NPC-CeO₂ composite by hydrothermal growth of CeO₂ onto the surface of Co@NPC.Ru/Co@NPC-CeO₂ catalyst was prepared by reduction of Ru³⁺using H₂/Ar gas mixture.It was indicated that Co is more conducive to electron transfer between Ceand Ru,thus promoting the creation of a Co-O-Cespecial structure and enhancing the synergistic effect with Ru.The Ru₁/Co@NPC-CeO₂-2 catalyst was tested to achieve a high turnover frequency（TOF）of 431.3 mol _H2·mol _Ru^-1·min^-1 and a low activation energy of 39.73 k J·mol^-1for the hydrogen production from AB hydrolysis.