Rational Design And Precise Preparation Of Anti-poisoning Catalyst In The Conversion Of Formic Acid To Hydrogen Energy

Hydrogen energy is an emerging energy carrier to support the decarbonization.Therefore,the production of hydrogen from renewable energy is today's top priority.However,the key for development of hydrogen economic lies in the production,storage,transportation as well as low-cost utilization of hydrogen.Among the many technologies for hydrogen production,storage and transportation,small organic molecules,such as formic acid(FA),as a high-density hydrogen storage chemical carrier,have obvious advantages in hydrogen energy storage and transportation.Regarding the utilization of hydrogen,proton exchange membrane fuel cells(PEMFCs)are attractive next generation power sources to replace the current internal combustion engine.However,they suffer extreme CO poisoning even at PPM level(<10 ppm),owning to the CO surface blockage on the-state-of-the-art Pt based catalyst.The allowance of using cheap crude hydrogen from steam reforming and thereby avoids the costly product separation has been dreamed ever since the emerging of the PEMFC technology.This work aims at the development of high-performance hydrogen energy conversion catalysts,focusing on two aspects of catalyst performance regulation and active site exploration.The main research contents are as follows:(1)Well-dispersed palladium nanoparticles anchored by a porous N-doped carbon are prepared by the microwave-assisted polyol method,wherein the porous N-doped carbon driven from the metal organic frameworks(ZIF-8)by heart treatment.The porous N-doped carbon materials were proved to be directly loading the Pd nanoparticles and the N contributing to anchor the nanoparticles and adjust the electronic structure between the metal nanoparticles and carrier.The prepared Pd/CZIF8-950 catalyst shows superior catalytic performance and selectivity for formic acid decomposition,the value of turnover of frequency up to 1166 h-1 and the mass activity up to 11.01 molH2g-1pdh-1 at 30?,which is higher than the Pd/C catalyst at the same condition.This activation strategy for preparing the porous N-doped carbon materials by heart measurement the metal organic frameworks provide an effective and easy way for synthesis the Pd-based catalyst,which has enormous application prospects for numerous catalytic reactions.(2)Proton exchange membrane fuel cell(PEMFC)is one of the keys enabling technologies for the transition to the upcoming hydrogen economy.However,one major detractor is its poor tolerance to carbon monoxide impurity,embodied by the markedly reduced operating energy efficiency even in the presence of trace level CO(10 ppm).Therefore,PEMFCs are now fed exclusively with pure hydrogen or purified hydrogen from steam reforming,being expensive and/or complicated.This problem can be settled if an efficient anti-poisoning anode electrocatalyst can be discovered to replace the current catalyst of choice,i.e.,Pt/C.Here we describe a new class of atomically dispersed IrRu-N-C anode catalysts for PEMFC,capable of òxidizing H2,CO,or a combination of the two.With small amount of Ir and Ru(24 ?gmetal cm-2)used in anode,H2 fuel cell performs peak power density at 1.43 W cm-2.When operating with pure CO,this new catalyst exhibits maximum current density at 800 mA cm-2,while the Pt/C based cell ceases to work.The CO turnover frequency reaches 68.6 s-1,even 1-2 orders of magnitude higher than the best CO catalytic removal catalysts.We attribute this exceptional CO oxidation performance to the interplay between Ir and Ru single atom centers,where the two sites act in synergy to favorably decompose H2O and to further facilitate CO activation.These findings open up a new avenue to conquer the formidable poisoning issue of PEMFCs.(3)The current materials used in proton-exchange membrane fuel cells(PEMFCs)are not sufficiently durable for commercial deployment.One of the major challenges lies in the development of an efficient,and CO-tolerant anode catalyst.Herein,we describe an IrRh@CZIF-8 dual metal catalysts for PEMFC anode,capable of oxidizing H2,CO,and the combination of two mixture gas.We find that these catalysts of function active distinct center atoms are high in catalytic efficiency for both H2 and CO,at negligible anode polarizations.With only 24 ug cm-2 of Ir and Rh used in the anode,the H2 fuel cell performs as good as that of Pt/C anode.When operating with pure CO,the cell exhibits a current density of 750 mA cm-2 at 0.21 V,while the counterpart Pt/C anode completely ceases to work.X-ray absorption fine-structure measurements reveal the presence of nitrogen coordinated structure of the Ir and Rh single atoms.These findings offer proof of concept that catalysts more robust than Pt can be synthesized to allow low temperature fuel cells working under challenging poisonous conditions.