Preparation And Catalytic Performance Of Palladium/Metal Oxide Catalysts For Hydrogen Production From Formaldehyde Aqueous Solution

Given the rapid development of the world economy and the accompanying global warming,the worldwide demand for economical and renewable energy has increased significantly.Hydrogen（H₂）energy is considered as an alternative energy feedstock to replace traditional fossil fuels for both environmental and economic concerns.The release of hydrogen from chemical hydrogen storage materials can solve the issue of the transport of hydrogen.Notably,the specific dehydrogenation reaction of formaldehyde（HCHO）aqueous solution can yield a theoretical hydrogen weight efficiency of 8.4 wt%under mild reaction conditions,which has attracted wide attention recently.The noble metal Pd exhibits excellent hydrogen production performance in the formaldehyde reforming reaction（FRR）due to its unique electronic structure.In addition,metal oxides can be used as ideal support materials with respect to their unique and versatile physicochemical property.Moreover,as active component is loaded on the carrier to form a host-guest material,the maximum utilization of the reactive site can be obtained.In order to reduce the loading amout of Pd and simultaneously improve the catalytic efficiency,a series of Pd/metal oxide catalysts were prepared to investigate their catalytic hydrogen production performance from aqueous formaldehyde solution.The research content is shown below:（1）Pd/Fe₂O₃ catalysts with different Pd contents supported on Fe₂O₃ were prepared by impregnation-precipitation method.Their structural and morphology features were characterized,and the catalytic performance of hydrogen production was systematically studied under a variety of conditions.By optimizing the loading capacity of Pd,the concentration of sodium hydroxide（Na OH）,formaldehyde（HCHO）and reaction temperature,it was proved that the hydrogen production rate of Pd/Fe₂O₃ catalyst can reach293.98 m L/min/g at 298.15 K when the loading capacity of Pd was 1 wt%,Na OH concentration was 1 M and HCHO concentration was 0.6 M.（2）The Pd/Bi/Bi OCl bimetallic nanocatalysts were prepared by one-step in-situ reduction of Bi OCl and Pd²⁺with Na BH₄.A systematic study of the effects of reaction parameters such as Na OH concentration and HCHO concentration on hydrogen production performance was carried out.Under the optimal reaction conditions,by adjusting the content of Pd in Pd/Bi/Bi OCl,the hydrogen production rate of Pd/Bi/Bi OCl-3%catalyst was 472.2 m L/min/g,which was 4.01 times that of pure Pd nanoparticles（NPs）,1.62 times that of pr-Pd/Bi OCl-3%,and 2.45 times that of Pd-Bi-3%.（3）The hydrothermally synthesized carbon quantum dots（CQDs）modified Ti O₂nanocomposites were used as a scaffold to prepare the supported Pd/CQDs/Ti O₂ as a catalyst to generate H₂ from an alkaline HCHO solution at ambient temperature.The catalytic reaction mechanism was investigated through a series of characterizations and further optimization of the reaction parameters.It was proved that the introduction of CQDs could activate the C-H bond of HCHO,thereby enhancing the catalytic hydrogen production activity of HCHO solution.When the loading amount of Pd was 3 wt%,the hydrogen production rate of Pd/CQDs/Ti O₂ catalyst was 176.67 m L/min/g within 30 min.