Multi-scale Structural Regulation Of The Performance Of Pd-based Catalysts In Formic Acid Dehydrogenatio

With the worsening environmental climate and the intensification of the energy crisis,the development of new energy has become the focus of countries,and the transition to clean energy has become a global consensus.As zero carbon energy source,hydrogen（H₂）plays a very important role in building a sustainable green energy system due to its advantages of renewable,clean,and pollution-free.However,storing and transporting H₂ in a safe and economical manner remains a challenge in developing the hydrogen economy.Therefore,developing sustainable in situ hydrogen production technology is an important means to solve this problem.Formic acid（FA,HCOOH）is a major product of biomass processing and CO₂ reduction.Due to its excellent stability,hydrogen content up to 4.4 wt.%,and low toxicity,it is considered to be one of the most promising hydrogen storage materials.However,the key to achieving this process is to design and prepare highly active and reusable catalysts that enable FA to release H₂ on demand under environmental conditions to meet the needs of practical applications.Based on this,this paper the FA dehydrogenation catalyst is regulated from the macro scale（morphology）,dispersion scale（particle size of active site）,and electronic scale（electronic environment of active site）.The main research contents are as follows:（1）Porous carbon carriers were prepared using peanut shell and melon seed shell as precursors.Pd/C catalysts with excellent performance were prepared by optimizing the amount of activator（ZnCl₂）and carbonization temperature.It was found that Pd metal was uniformly dispersed on the melon seed shell porous carbon carrier with a small particle size,and the catalyst had excellent hydrophilic properties.The initial turnover frequency value（TOF）is of the catalyst for catalytic decomposition of FA at30℃is 1597 h^-1,and the apparent activation energy is 37.60 KJ·mol^-1.（2）In order to further reduce catalyst cost and improve atomic utilization,CeO₂with different morphologies,sCeO₂（sphere）,oCeO₂（octahedron）,cCeO₂（cube）,and rCeO₂（rod）,were prepared through morphology control for anchoring Pd nanoparticles to prepare Pd-CeO₂ catalysts.The analysis shows that the Pd metal on Pd-sCeO₂ has ultra-fine size and good dispersion,and the electron transfer between Ce and Pd changes the electronic structure of the catalyst,which is the key to improving catalytic activity.The catalyst catalyzes the decomposition of FA at 50℃with a TOF of 870 h^-1 and an apparent activation energy of 57.71 KJ·mol^-1.（3）In order to further improve the catalytic activity of the catalyst,porous carbon carriers were prepared using melon seed shells as precursors,and different morphologies ofCeO₂ were used to construct Pd-xCeO₂/C heterostructures.The morphology,crystal surface,structure,and performance of the catalyst were comprehensively analyzed.Combined with density functional theory（DFT）calculations,the relationship between the decomposition performance of FA and the morphology and crystal surface ofCeO₂ was revealed.Studies have shown that sCeO₂on the（110）surface has abundant surface defects that can regulate the electronic state of Pd-sCeO₂ heterostructures.The catalyst catalyzes the decomposition of FA at 30℃with a TOF of 2691 h^-1 and an apparent activation energy of 20.41 KJ·mol^-1.