Highly Efficient Pd-based Nanocatalysts For Hydrogen Production From Formic Acid At Room Temperature

Hydrogen（H₂）plays an essential role in the construction of a sustainable energy system because of its renewable,clean,and pollution-free advantages.However,the safe storage and transportation of hydrogen remain critical challenges toward the construction of a sustainable energy system.Formic acid（FA,HCOOH）,a colorless and stable liquid at ambient conditions,with hydrogen-containing mass density and volume capacity of 4.4 wt%and 53.4 g/L,respectively,is considered to be an innoxious and convenient hydrogen supplier material that effectively avoids the problems of storage and transportation of hydrogen.The catalysts and reaction conditions greatly affect the decomposition pathway of formic acid through dehydrogenation and/or dehydration reaction.Therefore,the exploitation and fabrication of heterogeneous catalysts with excellent catalytic activity and selectivity for hydrogen production from formic acid at ambient conditions are urgently desired for the practical application of formic acid as a hydrogen storage material.In this paper,we have designed and synthesized a series of highly efficient Pd-based nanocatalysts for hydrogen production from formic acid at room temperature.The main research contents are given as follows:（1）A facile surfactant-free co-reduction method was successfully applied for the synthesis of novel PdAg-CeO₂/MC catalysts with exceedingly high catalytic activity for hydrogen production from formic acid.According to a series of characterization and catalytic performance test results,the amorphous CeO₂ with abundant oxygen vacancies can strongly coordinate with PdAg alloy nanoparticles and MC support and thus create intimate interfaces between PdAg and MC to improve electron transfer from MC and CeO₂ to the PdAg alloy nanoparticles to form an electron-rich surface.As a result,the as-synthesized PdAg-CeO₂/MC catalyst exhibits exceedingly high catalytic activity for formic acid dehydrogenation reaction with 100%hydrogen selectivity.The initial turnover frequency value（TOF）is 2272.8h^-1（HCOOH/HCOONa=1/6）at 303 K,and the value even reaches as high as 5244.8h^-1 at 353 K without the addition of sodium formate（HCOONa,SF）,which are comparable to the best heterogeneous catalyst ever reported.（2）A surface functionalization and co-reduction method was successfully applied to graft 3-aminopropyltriethoxysilane on the surface of mesoporous silica（SBA-15）to obtain amine-modified mesoporous silica（NH₂-SBA-15）used for anchoring IrPdAu trimetallic alloy nanoparticles.The obtained IrPdAu/NH₂-SBA-15catalyst was used as a highly efficient nanocatalyst for fast hydrogen production from formic acid at room temperature.A full of characterizations and catalytic performance test results indicate that ultrafine and electron-rich IrPdAu alloy nanoparticles are highly dispersied on the NH₂-SBA-15.The electronic synergistic effect between Ir,Pd,and Au metals and the strong metal-support interaction（SMSI）effect between IrPdAu alloy nanoparticles and NH₂-SBA-15 substrate give IrPdAu/NH₂-SBA-15 catalyst with abundant and accessible active sites.As a result,the IrPdAu/NH₂-SBA-15catalyst exhibits an extremely high catalytic activity,100%hydrogen selectivity,and good reusability for hydrogen production from formic acid at room temperature,giving record TOF values of 6316 h^-1（HCOOH/HCOONa=1/1）and 4737 h^-1（without HCOONa）at 298 K,which are among the highest values reported to date for all heterogeneous catalysts for formic acid dehydrogenation reaction.